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  • 1990-1994  (2,592)
  • 1980-1984  (1,923)
  • 1992  (2,592)
  • 1981  (1,923)
  • Analytical Chemistry and Spectroscopy  (2,485)
  • Biochemistry and Biotechnology  (1,126)
  • Physics  (490)
  • Physical Chemistry  (350)
  • Gas chromatography
  • Nuclear reactions
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  • 1990-1994  (2,592)
  • 1980-1984  (1,923)
Year
Keywords
  • 1
    ISSN: 1434-4475
    Keywords: Gas chromatography ; Polyphenyl ethers ; Lubricants, synthetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The described synthesis of synthetic lubricants based on polyphenyl ethers requires an analytical characterization of the isomerization step, which is important to the process optimization. The separation of the intermediates succeeds with gas chromatography; the isomers are determined using a retention index system. The obtained results are compared with the composition of the final product, which was investigated by HPLC analysis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1246
    Keywords: Stereometabolism ; Ethylbenzene exposure ; R- and S-mandelic acid ; Gas chromatography ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ethylbenzene is an important industrial solvent and a key substance in styrene production. Ethylbenzene metabolism leads to the formation of mandelic acid, which occurs in two enantiomeric forms, and phenyl-glyoxylic acid. To decide which enantiomer is preferably formed, 70 urine samples of exposed workers were taken at the end of shifts and — after 3-pentyl ester derivatisation — gas chromatographically analysed. The R/S ratio of mandelic acid enantiomers in urine amounts to 19:1, which means that R-mandelic acid is a major metabolite and S-mandelic acid is one of the minor urinary metabolites of ethylbenzene in man. The R/S ratio is independent of ambient air concentration of ethylbenzene within the investigated range. Compared to an ethylbenzene monoexposure the height of total mandelic acid excretion is decreased in the case of coexposure to other aromatic solvents.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 66 (1992), S. 298-299 
    ISSN: 1432-0738
    Keywords: 2,4-Dichlorophenol ; Accident ; Fatality ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case involving an accidental fatality resulting from skin absorption of 2,4-dichlorophenol in a factory is presented. The compound was quantified using gas chromatography after separation on a SP-1240 DA column and detection with flame ionization. Confirmation was obtained with mass spectrometry. Blood concentration was 24.3 mg/l. Other drugs, including ethanol, were not detected.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Activity coefficients ; 18-Crown-6-ether and tetraethyleneglycol dimethyl ether ; Thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The thermodynamic properties of different solutes at infinite dilution have been determined at 323.15 K. Deviations from ideality are discussed in terms of different contributions. The activity coefficients are compared with the calculated values by the one group contribution method.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 33 (1992), S. 103-112 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free fatty acids ; Cheese ; Programmed temperature vaporizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method with a capillary column and a programmed temperature vaporizer injector has been used to analyze the individual free fatty acids in cheese. The lipids were extracted from an acidified cheese slurry with diethyl ether and treated with tetramethylamonium hydroxide (TMAH) to convert the free fatty acids to tetramethylammonium soaps (TMA-soaps), which were subsequently pyrolyzed to methyl esters in the injector. Carrying out injection at the initial column temperature resulted in lower dispersion of the results, but the solvent front prevented quantitative determination of butyric and caproic acids, and an injector temperature of 300°C was therefore employed. Under the conditions tested, trimethylamine (tma) flash-off did not affect the determinations. The accuracy of the method improved at higher free fatty acid contents (coefficient of variation of 0.53% for a total free fatty acid content of 9000 mg/kg as opposed to 7.0% for a total free fatty acid content of 1400 mg/kg). The recovery rate for individual free fatty acids ranged between 91 and 103%.
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  • 7
    ISSN: 1612-1112
    Keywords: Gas chromatography ; coupling capillary columns ; Selectivity optimization ; Dual oven tuning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted procedure is presented for optimization of selectivity of tandem capillary columns with the same apolar (SE-54) stationary phase by varying column temperatures. The procedure is based on a threshold criterion calculated from the required resolution factor in which the separating power of the columns as a function of temperature is incorporated. The validity of the procedure has been verified by the analysis of a sample containing 33 hydrocarbons on two 31 m×0.3 mm i.d. SE-54 capillary columns coupled in series and by varying the temperatures of both columns in the range 60–100°C. At the optimum temperatures (70°C for the first and 92°C for the second column) 26 compounds were resolved equal to or better than Rji=1.00 in 22.8 min.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Carbon adsorbents ; Methyliodide ; Effect of KI on adsorption ; Thermodynamics of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography has been used to measure the adsorption at zero surface coverage of methyl iodide on different types of carbon. The effect on the adsorption of methyl iodide of adding potassium iodide to the carbon samples was also studied. The differences observed in the behaviour of these samples for the adsorption of methyl iodide are explained on the basis of the textural characteristics of the samples. Thermodynamic functions of adsorption of methyl iodide at zero surface coverage are obtained.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Partition coefficients ; Olive oil-nitrogen partition ; QSAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas-liquid chromatographic method has been used for direct determination of the partition coefficients (KD) of alcohols, ethers and ketones between olive oil and nitrogen. Olive oil was characterised as a stationary phase for gas chromatography. The differential molar enthalpies of solution were also calculated from retention data. Correlations between log KD for olive oil — nitrogen and molecular connectivity indices, differential molar enthalpies of solution, biological activity and partition coefficients for blood-air were obtained.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 621-626 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methyl and ethyl chloroformate ; Derivatization in the presence of water ; Alkyl and alkoxycarbonyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Phenolic acids, i.e. benzoic, phenylacetic, phenylpropenoic (cinnamic), phenylglycolic (mandelic), phenylpropionic and their variously substituted forms can be converted almost instantly to derivatives amenable to GC by treatment with methyl or ethyl chloroformate. The reaction, catalyzed by pyridine, proceeds even in the presence of water. The carboxylic group is esterified to the corresponding alkyl ester but even the alkoxycarbonyl ester (mixed anhydride) can be produced by altering the reaction conditions. Hydroxyl groups on the benzene ring or adjacent to the carboxylic group are converted to the alkoxycarbonyl ethers. Benzoic acid and some of its substitutents, unlike the other aromatic acids, shows a tendency to mixed anhydride formation even under conditions used for alkyl esters. A well deactivated capillary column with a thin film of stationary phase of low polarity enables even the mixed anhydrides to be analyzed successfully.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 163-165 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cyclodextrins ; Crown ethers ; Dimethylnaphthalene isomer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The twelve structural C2 isomers of naphthalene are resolved on a single capillary column using α, β, or γ cyclodextrin as the stationary phase. A change in elution order is seen upon going from α to β and then γ cyclodextrin which can be related to the size of the cyclodextrin cavity and the stereochemical fit of the isomer. A crown-ether column and a liquid-crystal column were found to be unable to separate all of the isomers.
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  • 12
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Partition coefficients ; Multiple headspace extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of “vapor phase calibration —VPC” where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 241-248 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Natural insecticides ; Marigolds ; Isolation of volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of optimizing Soxhlet and Simultaneous Distillation-Extraction (SSDE) procedures for the isolation of natural insecticides fromTagetes erecta, Tagetes patula, andTagetes minuta, members of theCompositae family, are presented. Extraction procedures were developed and validated that produced the extract with the highest degree of biocidal activity. The highest activity was obtained with extracts isolated by SSDE using methylene chloride. Initial work was carried out on a micro-SSDE. Preparative SSDE was used to provide large quantities of extracts for bioassays. Bioassays were used to govern optimization procedures usingAedes aegypti andAnopheles stephensi adults and larvae as target organisms.Tagetes minuta was determined to be the most active of the three species studied. Evaluation of activity and recovery versus extraction time was investigated. It was determined that an extraction time of ten hours resulted in the highest activity and over 90% recovery of the oils. Finally, supercritical fluid extraction of the flowers with CO2 was compared to SSDE.
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  • 14
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sociation constants ; Hydrogen bonding solutes ; Nearly ideal binary solvent theory ; Isosteric solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic data measured on mixtures of 19,24-dioctadecyldotetracontane, A≡C78, and 18,23-dioctadecyl-1-hentetracontanol, POH, allow the determination of the standard chemical potential of a solute on an ideal stationary phase with primary alcohol groups at ideal dilution. The Nearly Ideal Binary Solvent Theory provides the link between these data and the sociation constant of the solute with the primary alcohol. The method was applied to calculate sociation constants of a series of hydrogen bonding solutes. Results are compared with those determined by spectroscopy and calorimetry.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 398-410 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow technique ; Catalysis ; Hydrodenitrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Many important parameters of surface catalysed reactions can be determined simultaneously, under nonsteady state conditions using Reversed-Flow Gas Chromatography. A simple, slightly modified gas chromatograph is required. The distorted diffusion bands, obtained experimentally for reactant and product(s), can be analysed mathematically, using simple PC programs, to give the pre-exponential factors and the exponential coefficients of a function consisting of the sum of two-four exponential functions of time. From these, and some geometrical and diffusional characteristics of the reaction cell, the values of adsorption, desorption and reaction rate constants, the overall mass transfer coefficients in the gas and in the solid catalyst, and the adsorption equilibrium constant, for both reactant and product(s) can be calculated. The above parameters were determined at various temperatures and over three catalysts for the hydrodenitrogenation of piperidine ton-pentane, an industrially important hydrotreating process. The results obtained can help to understand the mechanism of reactions on solid surfaces and to confirm experimentally theoretical calculations on adsorption and surface reactions.
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  • 16
    ISSN: 1612-1112
    Keywords: Gas chromatography ; High-pressure Soxhlet extraction ; Organochlorine residue analysis ; Supercritical fluid extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The operational conditions of a high-pressure Soxhlet extractor (pressure, temperature, time and amount of sample) have been optimized, using carbon dioxide as extractant for the determination of organochlorine pesticides and polychlorinated biphenyls (PCBs) in certified potato, carrot, olive oil and lyophilized fish tissue samples. Good recoveries were obtained.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 475-478 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Telomeric fluoroalkanols ; Retention index ; Regression equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fluoroalkanols with the general formula H(CF2CF2)nCH2OH (n=1–8) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at three temperatures. A correlation between the retention index values, the molecular weights and the number of C and F atoms in the solute molecules was found.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 461-467 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Allyl thiocyanate and isothiocyanate ; Plant extract ; Analytical artifacts ; Isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Allyl thiocyanate and isothiocyanate were synthesized and could be analysed by gas chromatography without isomerization by keeping the injector at, or below, 50°C. Synthetic allyl isothiocyanate contained none of the isomeric thiocyanate but allyl thiocyanate contained 0.5% of isothiocyanate. The NMR spectra indicated both compounds to be free of the corresponding isomer. Analysis of extracts of stinkweed, mustard and horseradish by GC using non-isomerizing conditions showed that only the stinkweed extract contained allyl thiocyanate. Mustard and horseradish extracts contained allyl, and other, isothiocyanates but no allyl thiocyanate. Allyl thiocyanate previously reported in extracts of mustard and horseradish was most likely an artifact caused by partial isomerization of allyl isothiocyanate under the conditions of isolation and/or analysis.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 513-528 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    International journal of legal medicine 105 (1992), S. 65-68 
    ISSN: 1437-1596
    Keywords: Fire victim ; Exposure before or after death ; Carbon monoxide hemoglobin ; Gas chromatography ; Brandopfer ; Antemortale und postmortale Exposition ; Kohlenmonoxid-Hämoglobin ; Gaschromatographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Mit Hilfe der Gaschromatographie wurde die Kohlenmonoxid-Konzentration im Blut des rechten und linken Herzens vergleichend untersucht. Das Material stammt von Leichen mit antemortaler oder nicht-antemortaler Feuer- oder CO-Exposition. Das Konzentrationsverhältnis von COHb zwischen linkem und rechtem Herzblut (L/R-Quotient) scheint ein nicht brauchbares Kriterium zu sein, um festzustellen, ob der Tod sich vor oder nach der Feuer-Exposition ereignet hat; mit der Ausnahme von solchen Fällen, wo bei makrokopischer Untersuchung kein Ruß in den Atemwegen gefunden wird und wo die COHb-Konzentration innerhalb jener Grenzen ist, welche für Zigaretten-Raucher als normal angesehen werden.
    Notes: Summary Carbon monoxide hemoglobin (COHb) concentrations in left and right heart blood samples from cadavers both exposed and not exposed to fire or CO gas were analyzed by the gas chromatographic method. The COHb concentration ratio between samples of left and right heart blood (L/R ratio) does not appear to be useful for establishing whether death has occurred before or after exposure to fire with the exception of cases where no soot can be detected in the airways by the naked eye and the COHb concentration in the blood sample is within the level considered normal for tobacco smokers.
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992), S. 20-23 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A rapid, specific and reliable gas chromatographic assay procedure for Nifedipine in plasma has been developed. With a single-step solvent extraction, and electron capture detection, the method is sensitive to 0.5 ng/mL of plasma and the standard curve is linear from 0.5 to 500 ng/mL. Samples are protected from light to prevent formation of photodecomposition products. The method has been used to monitor drug concentrations in patients receiving therapeutic doses.
    Additional Material: 1 Ill.
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  • 22
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Blood group B antigenic trisaccharide-β-aminopropyl glycoside (B-TSAP) covalently attached to poly-N-(2-hydroxyethyl)acrylamide-coated porous glass interacts with anti-B monoclonal antibodies faster than the ligand coupled to CNBr-activated Sepharose 4B and Affi-Gel 10. Rates of hydrophobic adsorption of antibodies on the butyl derivatives of the same supports were measured to evaluate the diffusion input to overall kinetics. The lowest average affinity adsorption time [t1(aff) = 250 s] observed for polymer-coated glass probably arises because of the flexibility of the extended segments of chemisorbed N-substituted polyacrylamide acting as effective spacer arms.
    Additional Material: 3 Ill.
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  • 23
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Antibodies against gangliosides isolated from small tumour and nervous tissue specimens can be reliably detected in serum samples by the ganglioside electrotransfer technique without the need for previous purification steps. After separation by high performance thin layer chromatography gangliosides are transferred from silica gel plates to hydrophobic polyvinylidene difluoride membranes. These membranes are highly suitable for immuno-staining. The use of a 15-slit device allows simulataneous testing of up to 15 serum samples. Samples of serum from 39 patients with clear-cell carcinoma of the kidney, mammary carcinoma, ovarian carcinoma and neurological disorder together with samples from healthy controls were tested for anti-ganglioside antibodies from various tissues.
    Additional Material: 4 Ill.
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  • 24
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This paper describes a high performance liquid chromatographic (HPLC) method for determining 1,5-anhydroglucitol in plasma, in which anion exchange chromatography and pulsed amperometric detection are used. Plasma samples deproteinized with trichloroacetic acid are passed through a three-layer column packed with (1) strongly basic anion (BO3-3 form, the upper layer), (2) strongly basic anion (OH- form, the middle layer) and (3) strongly acidic cation (H+ form, the lower layer) exchange resins. 1,5-Anhydroglucitol is efficiently recovered in the flow-through fraction and interfering substances are completely removed by the column treatment. The analytical response of the method is linear with concentration to 40 mg/L, and it is possible to detect as little as 0.1 mg 1,5-anhydroglucitol per litre of plasma. Analytical recovery is between 96 and 103%, and there is good agreement between the results measured by our method and by a gas/liquid chromatographic method (r = 0.998). The method has been successfully used for the determination of very low 1,5-anhydroglucitol concentrations (〈 1 mg/L) in the plasma of diabetic patients.
    Additional Material: 2 Ill.
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  • 25
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The peroxyoxalate chemiluminescence(CL) detection method for the evaluation of the CL intensity of malondialdehyde(MDA) condensates with seven 2-thiobarbituric acid derivatives is described. The method consists of a flow injection technique together with a CL detection system using bis(2,4,6-trichlorophenyl) oxalate(TCPO) and hydrogen peroxide as chemiluminogenic reagents. Linear correlations between CL intensity and concentration are obtained for pmol levels of condensates. Among the condensates, 1,3-diethyl-2-thiobarbituric acid(DETBA)-MDA shows the largest CL intensity. High performance liquid chromatography (HPLC)/CL detection of DETBA-MDA and 1,3-diphenyl-2-thiobarbituric acid(DPTBA)-MDA using a mixture of TCPO and hydrogen peroxide in acetonitrile as a postcolumn reagent solution is also described. The detection limits for DETBA-MDA and DPTBA-MDA are 20 and 200 fmol, respectively, per 20 μL injection at a signal-to-noise ratio of 2. This HPLC/CL detection system was applied to the defermination of MDA in rat brains by using DETBA as a fluorescent derivatizing reagent.
    Additional Material: 7 Ill.
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  • 26
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: On the basis of the heparin-like effect of phosphotungstate (PTA), we have shown that it is useful for the purification of hepatitis-B virus surface antigen (HBsAg) using heparin-Sepharose affinity chromatography. HBsAg was eluted with 0.2-0.6 M NaCl. HBsAg was also eluted with PTA at approximately 1 mM, and the HBsAg fraction thus obtained contained fewer impurities than the corresponding fraction eluted with NaCl. Moreover, PTA yielded HBsAg and hepatitis-B virus e-antigen simultaneously. PTA may specifically reduce the affinity of HBsAg for heparin as well as simply competing with heparin for an anion-binding site of HBsAg. Residual PTA in the eluate was easily decomposed by alkalization, which was useful for subsequent studies.
    Additional Material: 2 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992), S. 91-94 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The use of capillary electrophoresis for simultaneous separation and detection of the two bipyridylium herbicides, paraquat and diquat, was investigated. Both herbicides were extracted from fortified sera with disposable ODS-silica cartridges. Separation was carried out using a capillary tube (50 μm i.d., 750 mm) of fused silica containing 10 mM glycine-HCl buffer (pH 3.0), 40 mM NaCl and 20% methanol as the carrier. Paraquat and diquat were completely separated in 10 min at an applied potential of 20 kV. On-column UV monitoring allowed detection of both herbicides simultaneously. The assay sensitivity was 0.05 μg/mL (signal-to-noise ratio, 2:1), which probably increases with increase in the sample volume of serum. Analytical recovery of both herbicides added to serum was about 97% at concentrations of 0.5-2.0 μg/mL.
    Additional Material: 3 Ill.
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  • 28
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive and simple reversed phase high performance liquid chromatographic (HPLC) method for the quantitative determination of free fatty acids in human serum is presented. The method is based on the direct derivatization of serum fatty acids with 6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone-3-propionylcarboxylic acid hydrazide. The derivatization reaction proceeds in aqueous solution in the presence of pyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 37°C. The resulting derivatives are separated within 75 min on a reversed phase column (YMC Pack C8) with a gradient elution of aqueous acetonitrile and detected fluorimetrically. The detection limits are 2.5-5 fmol in a 10 μL injection volume. The sensitivity permits precise determination of free fatty acids in 5 μL serum. The method is simple and is without the conventional liquid-liquid extraction steps of serum fatty acids.
    Additional Material: 2 Ill.
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  • 29
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive method for the determination of N-acetylneuraminic acid in human serum and urine is investigated. This method employs high performance liquid chromatography with chemiluminescence detection. N-Acetylneuraminic acid, released by hydrochloric acid hydrolysis of serum and urine, and N-glycolylneuraminic acid (internal standard) are converted into chemiluminescent derivatives with 4,5-diaminophthalhydrazide dihydrochloride, a chemiluminescence derivatization reagent for α-keto acids. The derivatives are separated within 35 min on a reversed phase column, TSKgel ODS-120T, with isocratic elution, followed by chemiluminescence detection; the chemiluminescence is produced by the reaction of the derivatives with hydrogen peroxide in the presence of potassium hexacyanoferrate(III) in alkaline solution. The detection limit for N-acetylneuraminic acid is 9 fmol (signal-to-noise ratio = 3). This sensitivity permits precise determination of N-acetylneuraminic acid in 10 nL of serum or 50 nL of urine. The method is applied to the determination of the N-acetylneuraminic acid in human sera from normal subjects and cancer patients and in normal urine.
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  • 30
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The content and dissolution rate of theophylline, diprophylline and proxyphylline from a sustained release formulation were determined by UV in situ densitometry. After separation the chromatographic zones corresponding to the spots of theophylline, diprophylline and proxyphylline on the high performance thin layer chromatographic plates were scanned in reflectance/absorbance mode at 275 nm. Quantification was performed with a second degree polynomial function over the range 40-200 ng for theophylline and 60-300 ng for diprophylline and proxyphylline. Percentages of dissolved theophylline, diprophylline and proxyphylline were monitored over 1, 3 and 6 h. The method was found to be simple, accurate, reliable, time-saving (up to 18 samples can be determined simultaneously) and low-cost.
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  • 31
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An improved method for the preparation of perbenzoylated ganglioside-derived sialic acids is described. After mild acid hydrolysis, isolation of sialic acids can be achieved by Folch partition (Method A) or by anion exchange chromatography (Method B). Perbenzoylated sialic acids were freed from benzoylation reagents by a second Folch partition. Total recoveries of both methods were found to be ≥90%, calculated from metabolically labelled gangliosides. Derivatized N-acetylneuraminic and N-glycolylneuraminic acids were separated and quantified by isocratic high performance liquid chromatography using a RP18 column as the stationary phase and methanol: water (8:2) as the mobile phase. Both sialic acids were completely separated and eluted as single peaks within 15 min, monitored by UV detection. As little as 20 ng of neuraminic acid could be detected, the detector being linear up to 5 μg tested.
    Additional Material: 5 Ill.
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  • 32
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two enzymes, phosphoglycerate mutase and peroxidase, were purified by using an immobilized metal ion adsorbent for the removal of unwanted proteins. The mutase was obtained pure from a single column, whereas the purification of peroxidase required the use of a thiophilic adsorbent in a tandem. The capacity was 2.5 mg pure peroxidase per mL gel.
    Additional Material: 6 Ill.
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  • 33
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    Biomedical Chromatography 6 (1992), S. 196-197 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The separation of tetracycline and amino glycopeptide antibiotics was achieved on silica gel thin layers. Tetracycline antibiotics were resolved on a Co+2 (1.0%) impregnated silica gel layer using ethanol:acetic acid: water (10:6:6, v/v/v) as the mobile phase. Amino glycopeptide antibiotics were separated on an untreated silica gel layer using the mobile phase n-butanol: formic acid: water (6:5:7, v/v/v). The spots of these antibiotics were located by exposing the chromatoplate to iodine vapours.
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  • 34
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    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992), S. 212-214 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 4 Ill.
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  • 35
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    Biomedical Chromatography 6 (1992), S. 222-223 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A new method for the quantification of famotidine consists of a simple extraction procedure and paired-ion high performance liquid chromatography with ultraviolet detection. The method has good accuracy and precision and should be suitable for the routine measurement of plasma and urine samples for clinical studies.
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  • 36
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    Biomedical Chromatography 6 (1992), S. 241-243 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive (1 ng/mL) and rapid method for the determination of naphazoline in rat plasma is described. Following extraction, the compound is analysed by reversed phase high performance liquid chromatography and ultraviolet detection at 214 nm.
    Additional Material: 3 Ill.
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  • 37
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    Biomedical Chromatography 6 (1992), S. 248-250 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A procedure for the solubilization and purification of cytochrome-P450 (cyt-P450) from human liver microsomes is described. Successive treatment of microsomes with protease XXVII and 3-(3-cholamidopropyl)dimethylammoniopropanesulphonic acid gave a solubilized cyt-P450 in more than 80% yield and with a three-fold increae in specific activity. With this treatment it was possible to eliminate 80% of cytochrome-b5 and 75% of NADPH cyt-P450 reductase. The solubilized cyt-P450 was filtered on a Sephacryl-200 column and then subjected to high performance liquid chromatography with a Mono-P column (chromatofocussing). The recovery of separated cyt-P450 was about 50% with a specific activity of 11.5 nmol cyt-P450/mg protein. Also with this technique it was possible to determinate the isoelectric points of cyt-P450. These results allowed us to confirm the usefulness of our method, for the study the cyt-P450 from surgical biopsies.
    Additional Material: 2 Ill.
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  • 38
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 39
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    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992), S. 255-257 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The retention behaviour of conjugated bile acids has been studied in a reversed phase high performance liquid chromatographic (RP-HPLC) system by using the mixture of methanol and aqueous phosphate buffer as the mobile phase. The retentions of the conjugates in RP-HPLC have been found to be mainly controlled by the glycine and taurine groups. The selectivity between five different glycine and taurine conjugated bile acids is a constant in RP-HPLC. This selectivity has been used for peak identification in the practical separation of conjugated bile acids.
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  • 40
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    Biomedical Chromatography 6 (1992), S. 263-263 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 41
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A combined high performance liquid chromatography/radioimmunoassay procedure is described for the simultaneous determination of dexamethasone (DEX) and its prodrug dexamethasone-21-sulphobenzoate sodium (DSS) in plasma. After precipitation of the plasma proteins by acetonitrile, the protein-free supernatant was injected onto a C18 reversed phase liquid chromatographic system and DSS- and DEX-containing fractions were collected. Hydrolysis of DSS by 0.01 N NaOH, followed by fractions extraction of both hydrolysed DSS and DEX fractions with ethyl acetate allowed the use of a dexamethasone-specific radioimmunoassay for the selective determination of both compounds. The method is accurate and reproducible (intraday variability for DSS and DEX〈6%, interday variability for DEX 14%), allowing quantification of DEX and DSS as low as 0.3 ng/mL and 0.7 ng/mL, respectively.
    Additional Material: 4 Ill.
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  • 42
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Vaginal organic acids have previously been detected by gas-liquid chromatography, but we have applied an ion exclusion high performance liquid chromatographic procedure to the analysis of vaginal discharge samples. This procedure has the advantage of not requiring derivitization of non-volatile acids and provides the convenience of a technique which does not require the use of flammable gasses, while allowing the identification of at least 18 different acids from the same chromatographic analysis. Vaginal discharge from women with symptoms of bacterial vaginosis was collected on weighed swabs and analysed for the presence of organic acids. The results were compared to the organic acid content of samples obtained from the same cohort of women after treatment with metronidazole. In addition, samples were obtained from asymptomatic women and these samples were analysed in the same manner. The number of organic acids present in samples from women with bacterial vaginosis was greater than the number found after treatment or among asymptomatic women. Succinic acid appeared to be inversely related to lactate concentration and succinate:lactate ratios were greater among women with bacterial vaginosis before treatment than after treatment. Liquid chromatography has proven useful as a means of evaluating the metabolic end-products of vaginal microorganisms in situ.
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  • 43
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    Biomedical Chromatography 6 (1992), S. 244-247 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: CGS 18102A is a novel hexahydrobenzopyranopyridine that has a mixed pharmacological profile of 5-HT-1A agonist and 5-HT-2 antagonist properties. Based upon these mechanisms, the compound is predicted to have anxiolytic efficacy with possible efficacy in depression. Preclinical studies in the rat have shown the drug to be well absorbed and extensively metabolized. Because of the anticipated low plasma levels in humans a gas chromatography/mass spectrometry (GC/MS) analytical method has been developed and validated to determine plasma concentrations of CGS 18102A in early clinical studies. The method utilizes CGS 18416A as the internal standard. Samples (1 mL) were extracted with pentane:ethyl acetate (75:25, v:v). Extracts were then concentrated and analysed directly by GC/MS. Separation was accomplished on a methylsilicone capillary column (30 m × 0.32 mm i.d.). GC/MS was carried out under positive ion ammonia CI conditions, with selected ion monitoring of the [M + H]+ ions (m/z = 262 and 248) for CGS 18102A and CGS 18416A, respectively. The method was successively applied to the analysis of clinical samples from an ascending multidose safety and tolerability study conducted in six normal healthy male volunteers.
    Additional Material: 3 Ill.
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  • 44
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A selective and sensitive method for the determination of low molecular weight aliphatic primary amines in urine is described. These amines were converted into their benzenesulphonyl derivatives by a modified Hinsberg procedure, and measured by gas chromatography with flame photometric detection (FPD-GC) using a DB-1 capillary column. The derivatives were very stable and provided excellent FPD responses. By FPD-GC, linear calibration curves were obtained in the range 10-200 ng of methylamine, ethylamine, n-propylamine, isobutylamine and n-butylamine using tert-butylamine as an internal standard, and the detection limits of these amines were ca. 6-25 pg as the injection amount. Benzenesulphonamide derived from ammonia was converted into its N-dimethylaminomethylene derivative which has a longer retention time, and separated from benzenesulphonyl derivatives of low molecular weight primary amines on the chromatogram. The recoveries of aliphatic primary amines added to urine samples were 91-107% and the relative standard deviations were 0.2-4.5%. Analytical results of aliphatic primary amine contents in urine samples of normal subjects are presented.
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  • 45
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 46
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    Biomedical Chromatography 6 (1992), S. 269-277 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Several polymer-bound o-nitrobenzophenone reagents containing different detector-sensitive tags have been combined in the same reactor for the on-line derivatization of amine samples. The formation of multiple derivatives allows numerous opportunities for quantitation from the same injection, and also allows improved identification from the retention times of the multiple derivatives. Changing the reaction conditions changes the ratio of the products formed, so that changes in the ratio of peak heights and areas can also be used for analyte identification. In this work, propylamine was derivatized in acetonitrile on-line, precolumn. Changing the reaction conditions, of reaction time, temperature, solvent, presence of catalyst and the components of the reactor, changed the ratio of the derivatives formed. These changes in product formation with changing reaction conditions were applied to the identification and quantitation of amphetamine and methamphetamine in urine. The drugs were identified by the retention times of their derivatives, the ratio of te peak areas of the derivatives and the change in the ratios after changing reaction conditions. Each derivative was also used for quantitation of levels of spiked concentrations of amphetamine and methamphetamine, with relative errors less than 8%.
    Additional Material: 7 Ill.
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  • 47
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic method was developed for the simultaneous assay of R(-)- and S(+)-albuterol in human serum. The assay involves solid phase extraction as a sample clean-up step and derivatization of racemic albuterol to its diastereomeric thioureas with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl isothiocyanate. Chromatographic separation was accomplished under isocratic conditions using an octadecylsilane column and a mobile phase consisting of 29:71 acetonitrile:distilled water containing 0.1% triethylamine, pH 4.0 (adjusted with concentrated phosphoric acid) at a flow rate of 0.8 mL/min. The diastereomers were detected using a fluorescence detector set at 223 nm excitation and no emission filter. Racemic bamethane was used as internal standard. Drug to internal standard peak-height ratios were linear over a 2-20 ng/mL range for each enantiomer. The limit of detection of each analyte was 1.0 ng/mL (S/N = 3).
    Additional Material: 5 Ill.
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  • 48
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A fully automated assay for the analysis of ranitidine in serum and plasma, with and without an internal standard, was validated. It utilizes robotic solid phase extraction with on-line high performance liquid chromatographic (HPLC) analysis. The ruggedness of the assay was demonstrated over a three-year period. A Zymark Py Technology II® robotic system was used for serial processing from initial aspiration of samples from original collection containers, to final direct injection onto the on-line HPLC system. Automated serial processing with on-line analysis provided uniform sample history and increased productivity by freeing the chemist to analyse data and perform other tasks. The solid phase extraction efficiency was 94% throughout the assay range of 10-250 ng/mL. The coefficients of variation for within- and between-day quality control samples ranged from 1 to 6% and 1 to 5%, respectively. Mean accuracy for between-day standards and quality control results ranged from 97 to 102% of the respective theoretical concentrations.
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  • 49
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    Biomedical Chromatography 6 (1992), S. 9-11 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A specific method for the determination of 10α-methoxy-9,10-dihydrolysergol, a nicergoline metabolite (metabolite 2), in urine is described. Metabolite 2 was well separated from the urine components on a reversed phase column, Hypersil ODS 5 μm, using an acetonitrile: pH 3.5 phosphate buffer (40:60, v/v) as the mobile phase at a flow rate of 1 mL/min. UV detection was set up at 220 nm. After addition of a known amount of lysergamide as the internal standard, the compounds were extracted from alkalysed urine on a pre-packed glass column (Extrelut 1) with dichloromethane. With 0.5 mL urine, concentrations down to 0.56 μmol/L could be determined.
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  • 50
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This paper describes a method for the direct gas/liquid chromatographic (GC) analysis of 46 glycine-conjugated bile acids, which differ from one another in the number, position and configuration of the hydroxyl groups at positions C-2, C-3, C-4, C-6, C-7 and/or C-12. Free bile acids were converted quantitatively on a micro scale to ethyl ester-trimethylsilyl (Et-TMS) and methyl ester-dimethylethylsilyl (Me-DMES) ether derivatives of the corresponding glycine conjugates. The Et-TMS and Me-DMES ethers of the glycine conjugates were chromatographed on an aluminum-clad flexible fused-silica capillary column coated with a thin film (0.1 μm) of chemically bonded and cross-linked methylpolysiloxane. Relative retention time (RRT) and methylene unit (MU) values were determined for the 46 compounds and their GC behaviour was discussed. The derivatization procedure and the retention data would be useful for the direct GC identification of unknown glycine-conjugated bile acid mixtures extracted from biological samples.
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  • 51
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    Biomedical Chromatography 6 (1992), S. 24-29 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method for the determination of the antiepileptic drug valproic acid and 14 of its metabolites in serum and urine by gas chromatography/mass spectrometry with selected ion monitoring of the trimethylsilylated derivatives has been developed. Sample preparation, including hydrolysis of VPA-conjugates and removal of urea in urine is carried out at pH 5.0 and is rapid and simple. The samples are extracted with ethyl acetate and the concentrated extracts are trimethylsilylated. Analysis with adequate separation of metabolites is achieved with a DB 1701 fused silica (Megabore) capillary column. The method exhibits high recovery and reproducibility and is sufficiently sensitive and selective for analysis of small sample volumes. Application of the method for screening patient serum and urine samples for unusual metabolite patterns, with possible predictive value for early detection of liver injury, is presented.
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  • 52
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    Biomedical Chromatography 6 (1992), S. 108-108 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 53
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic (HPLC) method has been developed to permit the rapid comparison of acidic polysaccharides of diverse compositions and the sensitive determination of their constituents. It is based on two combined analyses of the polysaccharide hydrolysates - a separation of the released compounds by ion-moderated partition chromatography with UV detection at two wavelengths and a separation of the sugar dansylhydrazine derivatives by reversed phase chromatography. The former permits identification and quantitation of uronic and carboxylic acids, the latter permits more sensitive and specific determination of the neutral aldoses. Some bacterial exopolysaccharides have been used to demonstrate the validity of this HPLC procedure for the chemical characterization of uronic acid-containing polysaccharides. This method appears to be useful for studying capsular polysaccharides, which are involved in the evasion of phagocytosis by pathogenic bacteria.
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  • 54
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and α-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: α-santalol 6.1 ng/mL, β-santalol 5.3 ng/mL and α-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with α-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively.
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  • 55
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive and simple method for the determination of prostaglandins (PGs) by HPLC with fluorescence detection is described. PGs are converted to the corresponding fluorescence derivatives by the reaction with 4-(N,N-dimethylaminosulphonyl)-7-(1-piperazinyl)-2,1,3-benzoxadiazole (DBD-PZ) in the presence of 2,2′-dipyridyl disulphide and triphenyl phosphine in acetonitrile. The reaction is completed at room temperature after 30 min. The DBD derivatives of nine PGs are separated within a single 45 min chromatographic run on a reversed phase ODS column with a linear gradient elution using water and acetonitrile. The detection limits (signal-to-noise ratio of 3) calculated from the standard mixture of PGs (6-keto-F1α, F1α, F2α, E1, E2, D2, limaprost, A1 and B1) are in the range 1.7-5.0 fmol. The applicability of the proposed procedure is evaluated to the detection of PGs added to rat plasma.
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  • 56
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    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 57
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    Biomedical Chromatography 6 (1992), S. 183-190 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method for the extraction and quantification by high performance liquid chromatography (HPLC) of non-labelled benzodiazepines partitioned into biological membranes has been developed. The benzodiazepine (BZD) was partitioned in a synaptosomal membrane-buffer system. The membranous pellet was separated by centrifugation and from this pellet, previously submitted or not to a proteolytic treatment and resuspended in the same buffer, the BZD was extracted by the addition of the proper volume of ethyl acetate, i.e. that capable of extracting at least 99.5% of the total drug in the aqueous phase. Optimal conditions for maximum proteolysis were: incubation of membranes at a final concentration of 1 mg protein/mL in the presence of 0.08 mg of Protease type I per mL for 90 min. at 45°C. Although the efficiency of the proteolysis was demonstrated not only by kinetic but also by electrophoretic evidence, recovery of BZD in the organic solvent was not increased by the enzymatic treatment at a mass BZD/protein ratio in the range 4-4.6 10-5 μg BZD/mg protein. For the HPLC quantification a reversed phase ODS column was used with methanol: water (1:1) plus 3.5% acetic acid as the mobile phase at a constant pressure and 1 mL/min flow rate. The UV detector was calibrated at 265 nm. Calibration curves were constructed by plotting peak height or peak area vs. nmoles BZD and adjusted to straight lines by a regression analysis by the least squares method. The peak height was selected as the detection method. Intra- and inter-assay precision did not exceed 10% and the total recovery was 100%.
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  • 58
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A reversed phase high performance liquid chromatographic method for the simultaneous determination of pseudouridine (PU) and creatinine (Cr) in urine is described. The mobile phase was 0.01 mol phosphate buffer (pH 6.1) containing 2.5 mmol octanesulphonic acid as the ion pairing agent. UV detection was set at 250 nm. Variation in pH value affected the retention time of PU and Cr significantly; Their separation from interfering peaks was also affected. The recoveries of PU and Cr were 89.93% and 90.35%, respectively. The standard deviation of the method for PU was 48.69 ± 0.063 (nmol/μmol Cr, mean ± SD, n = 5). The urine samples from 233 normal children of different ages and 119 patients with leukaemia were analysed by this method. The normal reference value was appraised by comparison with the percentage of immature cells in the bone marrow. The results showed that the sensitivity of the method was 94.12%, the specificity was 95.86%, the accuuracy was 95.50%, the positive predictive value was 82.05% and the negative predictive value was 98.78%. The method can be used to evaluate the state of the leukaemia, and to monitor the effect of treatment.
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  • 59
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    Biomedical Chromatography 6 (1992), S. 205-211 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Zn-metallothioneins (MT-1 and MT-2) were isolated and purified from Wistar rat liver induced by subcutaneous injection with cadmium chloride over a short time. Instead of Sephadex G-50 and DEAE Sephadex A-50, new chromatographic media produced by Pharmacia, Sephacryl S-200, S-100 and DEAE Sepharose Fast Flow were used in the purification of metallothioneins. The time required for purification with the new method was only 1/3 that required with the usual method and had the same purification effect and rate of recovery. The number of mercapto groups measured with modified Ellman's reagent and cysteine as standard is 20 in MT molecules. Zn and Cd concentrations in each fraction were measured by single sweep polarography rather than atomic absorption spectrophotometry. MT-1 and MT-2 contained 6 gram atoms of zinc, but no cadmium. Purified MT-1 and MT-2 were shown by high performance liquid chromatographic analysis to be highly homogeneous and had an amino acid composition similar to that of Cd-MT.
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  • 60
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    Biomedical Chromatography 6 (1992), S. 224-226 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Haemoglobin obtained from a male adult Ghanian with retinopathy, which was probably caused by haemoglobinopathy was analysed by capillary electrophoresis (CE) for clinical diagnosis. Two major peaks, which were in the ratio of nearly one, were detected. The elution times of these peaks (HbXI and HbXII) were faster than that of normal haemoglobin (HbA). The existence of two different abnormal types of haemoglobin was clear in the patient blood. The following sequence analysis revealed that the first peak (HbXI) was HbC and the second (HbXII) was HbS on the electropherogram, and that the patient was a heterozygote of HbS and HbC (HbSC disease). One of the diagnostic processes in a haemoglobin disease was shown by the combined use of CE, HPLC and a protein sequencer.
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  • 61
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    Biomedical Chromatography 6 (1992), S. 236-240 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An analytical method has been developed for the determination of a new antiepileptic drug, CGS 18416A, in human plasma. CGS 18416A is a new anticonvulsant representative of a novel class of water-soluble agents being developed for the treatment of epilepsy. Preclinical trials indicate sustained efficacy at relatively low oral doses, indicating a need for a sensitive assay. The method is based on capillary gas chromatography/mass spectrometry and utilizes stable isotope-labelled CGS 18416A as the internal standard. Samples (1 mL) are acidified, then washed with pentane/ethyl acetate, followed by liquid/liquid extraction at pH 11 with pentane/ethyl acetate. Extracts are then concentrated and analysed directly by gas chromatography/mass spectrometry. Separation is accomplished on a thick film methylsilicone capillary column. Mass spectrometry was carried out under positive ion ammonia Cl conditions with selected ion monitoring of the protonated molecular ions (m/z = 248 and 252) for CGS 18416A and the 13CD3-CGS 18416A, respectively. Specificity was demonstrated by the lack of interfering peaks at the retention time of CGS 18416A and the internal standard. Recovery and reproducibility assessments indicate good accuracy and precision over the validated concentration range of 0.2-51 ng/mL. The limit of quantification is 0.2 ng/mL and the method has sufficient sensitivity to support clinical trials. This is illustrated with an example of quantification in a normal volunteer following oral dosing.
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  • 62
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    Biomedical Chromatography 6 (1992), S. 106-107 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 63
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    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 64
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive determination method for a non-fluorescent anti-arrhythmic drug, mexiletine, in rat plasma is presented utilizing a HPLC peroxyoxalate chemiluminescence (PO-CL) detection system. After an internal standard (4-methylmexiletine, 4.35 pmol) and 0.1 N sodium hydroxide solution were added to 5 μL rat plasma, the solution was poured onto an Extrelut 1 column. Both mexiletine and the internal standard were eluted with diethy ether and then the eluate was evaporated to dryness. The residue was dissolved in 0.2 M borate buffer (pH 8.5) and mixed with dansyl chloride (75 nmol) in acetronitrile. After standing of 90 min at room temperature, 0.5 N HCI was added to the reaction mixture to stop the reaction and a 2/45 aliquot of the mixture was subjected to a HPLC PO-CL detection system using bis(4-nitro-2(3,6,9-trioxadecyloxycarbonyl)phenyl)oxalate (TDPO) and hydrogen peroxide. The calibration curve for mexiletine in rat plasma was linear over the range 20-100 ng/mL plasma (20.6-103 fmol/injection). The detection limit (S/N = 2) was 1.0 fmol over the whole procedure. The method was applied to the measurement of the time courses of plasma mexiletine concentration after oral administration of the drug [25 mg (115.9 μmol)/kg] to rats.
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  • 65
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    Biomedical Chromatography 6 (1992), S. 162-162 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 66
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The increased attention on the therapeutic implications of stereoisomerism has provided an impetus for the development of analytical methods for enantiomeric separation. The indirect method of separation of enantiomers as diastereomers using high performance liquid chromatography (HPLC) has emerged as an efficient and versatile approach. This is due mainly to the availability of numerous chiral derivatization reagents (CDRs). This article reviews CDRs useful for the development of an indirect HPLC method using ultraviolet, fluoresence and electrochemical detection. In addition, factors crucial for the development of the indirect method are discussed.
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  • 67
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    Biomedical Chromatography 6 (1992), S. 194-195 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Hageman factor fragment (HFf) concentrate was prepared from acetone and dextran sulphate activated human plasma by chromatography on a CM-Sephadex column. The preparation was free of the main kallikrein inhibitors - Cl-inactivator, α2-macroglobulin, antithrombin III and α1-antitrypsin. The HFf concentrate can serve as an activator of prekallikrein in patient plasma.
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  • 68
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    Biomedical Chromatography 6 (1992), S. 198-204 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive method for the determination of hyoscine (scopolamine) in urine is described. After concentration and “clean-up” on C18 and CN solid phase extraction columns, hyoscine was quantified by high performance liquid chromatography with coulometric detection (oxidation at +0.9 V). The limit of detection was 5 ng per sample and the precision for 5 mL samples containing 2 ng/mL was 12.3%. The method was applied to urine samples collected from 12 volunteers wearing Scopoderm TTS patches. The mean excretion rate of unmetabolized hyoscine was 0.45 μg/h and 87% of the total hyoscine was present as conjugates. Apohyoscine (aposcopolamine) was identified as a urinary metabolite. The significance of this with regard to hyoscine assays is discussed.
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  • 69
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    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 70
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    Biomedical Chromatography 6 (1992), S. 227-230 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A new method for the detection of gangliosides based on the lipophilic fluorescence agent 4-(N,N-dihexadecyl)amino-7-nitrobenz-2-oxa-1,3-diazole (NBD dihexadecylamine) and its application for preparative high performance thin layer chromatography is described. Brain gangliosides were chromatographed on silica gel coated thin layer plates and located with non-destructive fluorochrome under longwave ultraviolet light. The fluorescent zones were scraped off and the gangliosides were extracted with a mixture of chloroform/methanol/water (30/60/8; v/v/v). The gangliosides were separated from uncharged NBD dihexadecylamine by anion exchange chromatography and impurities were removed by Iatrobeads chromatography. The method described offers a simple and succesful preparative thin layer chromatographic strategy to obtain pure gangliosides in microgram and milligram quantities.
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  • 71
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    Biomedical Chromatography 6 (1992) 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 72
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A gas chromatographic/mass spectrometric procedure has been developed for the quantiation in human plasma of the enatiomers of rimanatadine and its three hydroxylated metabolites. The assay utilized derivatization of all analytes with the optically active reagent S-α-methyl-α-methoxy(pentafluorpheyl)acetic acid, selective ion monitoring, methane negative ion chemical ionization mass spectrometry and stable isotope dilution techniques. This method has been used to meausure plasma concentrations of the enantiomers of rimantadine, m-hydroxyrimantadine and p-hydroxyrimantadine (equatorial and axial epimers) in the ranges 2.5-250, 2.5-50, 1.25-62.5 and 1.25-62.5 ng/mL, respectively, in six subjects given a single 200 mg dose of racemic rimantadine. Although there are no significant differences in the concentration-time profiles of R- and S-rimantadine, large stereospecific differences in the disposition of their metabolites are observed.
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  • 73
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    Biomedical Chromatography 6 (1992), S. 53-53 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 74
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    Biomedical Chromatography 6 (1992), S. 84-87 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A universal peroxyoxalate-chemiluminescence detection system for high performance liquid chromatography, available for a variety of mobile phases, has been developed. The system consisted of a dual-head short-stroke pump and a chemiluminescence detector. The standard conditions using bis(2,4,6-trichlorophenyl) oxalate (TCPO) as aryl oxalate were as follows. The first postcolumn solution was the mixture of 0.5 M imidazole-nitric acid (pH 7.5) and acetonitrile (1:4, v/v). The second was acetonitrile containing TCPO-hydrogen peroxide. These two solutions were delivered by the two pump-heads. After the pH of the column eluate was adjusted to the optimum range (6.5-7.5) by the first postcolumn solution, the solution was mixed with the second postcolumn solution. After flowing through a reaction coil, the chemiluminescence of the mixture was monitored. Using this system, a high sensitivity (fmol level) was obtained for perylene as an analyte with mobile phases having different pH values (2.0-8.0). Polycyclic aromatic hydrocarbons became detectable to a high sensitivity even after the column separation using an acidic mobile phase. The detection sensitivity of nitrated pyrenes after on-line electrochemical reduction using an acidic mobile phase was also increased. This system might be available for other aryl oxalates by some modifications of the postcolumn solutions.
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  • 75
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    Biomedical Chromatography 6 (1992), S. 99-105 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The plasma concentrations of metoprolol enantiomers have been determined by means of a direct phenyl carbamate-cellulose-based chiral high performance liquid chromatography assay using fluorimetric detection. This assay has been used to investigate the pharmacokinetics and pharmacodynamics of metoprolol enantiomers in the conscious goat. There is evidence that the pharmacokinetics of metoprolol in the goat occurs stereoselectively and that enantiomer-enantiomer pharmacokinetic interactions occur. R-Metoprolol is less effective in reducing the mean arterial blood pressure than S- and R/S-metoprolol.
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  • 76
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    Biomedical Chromatography 6 (1992), S. 59-62 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The method for the simultaneous determination of angiotensin-converting enzyme (ACE) inhibitor enalapril and its active metabolite enalaprilat in plasma and urine was developed by gas chromatography/mass spectrometry. Enalapril and enalaprilat in plasma and urine were extracted and cleaned up by using Sep-Pak C18 and silica cartridges. Derivatization was carried out using diazomethane and trifluoroacetic anhydride. Detection by selected ion monitoring was selected to m/z 288 (enalaprilat) and 302 (enalapril). The detection limit of enalapril and enalaprilat was 200 pg/mL in plasma and 2 ng/mL in urine. This method was applied to the pharmacokinetic analysis of enalapril and enalaprilat in body fluids.
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  • 77
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A highly sensitive and selective method for the determination of spermidine and spermine has been developed. A polyamine oxidase (Aspergillus terreus) immobilized column was used as a postcolumn reactor. The detection limit was 0.2 pmol/injection for both spermidine and spermine with a linear range of three orders of magnitude.
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  • 78
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive and specific high performance liquid chromatographic method is described for measuring imidazole dipeptides and 3-methylhistidine in human muscle biopsies, serum and urine. Muscle extract, serum or urine was reacted with o-phthaldialdehyde and the derivatives were separated by reversed phase chromatography with column swithing and fluorescence detection.
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  • 79
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    Biomedical Chromatography 6 (1992), S. 35-38 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple and rapid method for analysis of the core of 2′,5′-oligoadenylates, mainly based on the use of high performance liquid chromatography (HPLC), is described. Perchloric acid extracts of tissues or cells were first treated with nuclease P1. Portions of the extracts were then digested with alkaline phosphatase. HPLC analysis of the extracts was performed on a column system composed of an Ultrasphere ODS precolumn (4.6 × 45 mm) and an Ultrasphere Octyl column (4.6 × 250 mm) by stepwise elution using a 50 mM ammonium phosphate buffer, pH7, containing 3.5 and 7% methanol. Three species of the core of 2′,5′-oligoadenylates (dimer, trimer and tetramer) from a number of samples were eluted separately with 7% methanol, and the concentration of each core was directly estimated using constant values calculated with the standard core. The level of the core of 2′,5′-oligoadenylates in tissues and cells determined by our method is similar to that reported by other authors who used biological, radiobinding or radioimmunological assays.
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  • 80
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    Biomedical Chromatography 6 (1992), S. 50-52 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Orosomucoid, a member of the lipocalin family, may function in the in vivo transport of lipophilic compounds such as basic and neutral drugs. We describe the identification of 7-chloro-1-methyl-1,5-benzodiazepine-2,4-dione (clobazam) bound to the serum orosomucoid from individuals actively taking this tranquillizer. This suggests not only that other endogenous factors limit access to the benzodiazepine binding site on human serum albumin, but also that the differential binding of benzodiazepines and their metabolites by orosomucoid should be considered in determining therapeutic doses, particularly in the acute phase response.
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  • 81
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    Biomedical Chromatography 6 (1992), S. 278-282 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An automated analytical method utilizing laboratory robotics has been developed and validated for quantifying concentrations of a new antiepileptic drug candidate (CGP 33101) in human plasma. The robotic system aliquots the biological sample, adds the internal standard (CGP 23901) and pH 12 buffer, extracts the compounds from the basified matrix into an organic phase (methyl-t-butyl ether:dichloromethane, 2:1) and concentrates the extracts for reversed-phase, high performance liquid chromatographic (HPLC) analysis. The robotic system is directly interfaced with the HPLC system. Separation is achieved on a Hypersil 3 μm C18 column (4.6 × 50 mm) with ultraviolet detection of the analytes at 230 nm. Specificity was demonstrated by the lack of interfering peaks at the retention times for both the drug and internal standard. Recovery and reproducibility assessments indicated good accuracy (overall mean relative recovery of 102.7%) and precision (coefficient of variation of 4.4 to 7.7%) for CGP 33101 over the concentration range of 50-4000 ng/mL. The limit of quantification (LOQ) is 50 ng/mL. The method has been successfully applied to a clinical study in which normal volunteers received single oral doses of 400--1200 mg of this new drug candidate.
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  • 82
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    Biomedical Chromatography 6 (1992), S. 287-290 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The technique of high performance immunoaffinity chromatography was used to measure the levels of recombinant interferon in chronic lymphocytic leukaemia patients enrolled in a phase II recombinant interferon clinical trial. The technique employed a short high pressure chromatography column packed with minute glass beads which had monoclonal antibody, directed against recombinant alpha interferon, immobilized to their surface. This system was used to measure interferon levels in a variety of different human body fluids. A good correlation was found when interferon levels, detected by chromatographic separation, were compared to levels obtained by a conventional radioimmunoassay.
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  • 83
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    Biomedical Chromatography 6 (1992), S. 258-258 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 84
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    Biomedical Chromatography 6 (1992), S. 259-262 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 85
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    Biomedical Chromatography 6 (1992), S. 265-268 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Six estrogens - estrone, equilin, estradiol, sodium estrone sulphate, sodium equilin sulphate and sodium 17-α-dihydroequilin sulphate in dog serum were successfully separated and quantified by a high performance liquid chromatographic method developed in our laboratories. The mobile phase was optimized by studying the effects of an organic modifier (acetonitrile) and an ion pairing reagent (tetrabutylammonium hydroxide). The serum sample work-up procedure was designed to recover both conjugated and unconjugated estrogens. The optimum method involved acetonitrile to precipitate serum proteins/peptides and extract estrogens. Residues were reconstituted in 50% acetonitrile in water for injection. The detection limits for these six estrogens via UV detection ranged from 0.5 to 5 ng on-column with a signal-to-noise ratio (S/N) of 10 for a 20 μL injection and via fluorescence 0.1 ng on-column for 17-β-estradiol. Validation data are included for all six estrogens.
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  • 86
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A sensitive and selective liquid chromatographic method to quantitate MDL 201,012 in human plasma was developed and validated. MDL 201,012 (I), diethyl-MDL 201,012 (internal standard, II) and desmethyldiol-MDL 201,012 (masking agent, III) were isolated from basified plasma (2 mL) by solid phase extraction using Bond-Elut® C-18 cartridges. Endogenous components were selectively removed prior to eluting the analytes from the sorbent. Components were separated using on-line LC column switching with a cyanopropyl precolumn and a phenyl analytical column. The analytical column effluent was monitored electrochemically at a glassy carbon electrode at a potential of + 1025 mV vs. Ag/AgCI. Peak-height ratios were proportional to the amount of MDL 201,012 added to plasma over the range 125-7500 pg/mL MDL 201,012. Absolute recovery of MDL 201,012 from human plasma was 〉94% across the calibration range. The minimum quantitation limit was 125 pg/mL. Assay precision (%RSD) ranged from 5.2 to 13% based on the analysis of quality control standards containing 125, 250, 500, 1000, 2500, 5000 and 7500 pg/mL MDL 201,012. Corresponding assay accuracy (% relative error) was ±8.5%. The method has been successfully used to quantitate MDL 201,012 in samples from acute dose tolerance studies in human volunteers.
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  • 87
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic method for the analysis of chlortetracycline (CTC) using postcolumn fluorescence detection has been developed. After chromatographic separation of CTC on a polystyrenedivinylbenzene copolymer column, a highly fluorescent derivative isochlortetracycline (iso-CTC) was formed postcolumn in an on-line reaction coil with the addition of 25% NaOH (w/v). Chromatographic separation was achieved on a PRP-1 column, 15 cm × 4.6 mm, with 27:73 acetonitrile:0.2% perchloric acid (v/v), at 1.0 mL/min. Fluorescence derivatization was achieved by the on-line addition of 25% NaOH (w/v), at a flow rate of 0.2 mL/min, into the column eluant in a post-column reaction coil. The reaction coil was 9 m of teflon (1/16 in o.d., 0.3 mm i.d.) knitted into a six-sided coil. The fluorescent derivative was detected at λex 355 nm and λem 〉389 nm. Using this method after a simple sample cleanup, CTC can be detected in milk at 0.04 μg/mL, which is comparable to that obtained by microbiological assays. The detection method was linear between 0.02 μg/mL and 4 μg/mL. Because of the chromatographic separation, the method is more selective than microbiological assays and more sensitive than ultraviolet detection. With the chromatographic system described, the keto tautomeric forms of CTC and 4-epi-CTC are separated in a system which minimizes their formation on-column. In acidic aqueous organic solutions, the keto tautomer of CTC is the only product formed to any significant amount.
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  • 88
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    Journal of Chemometrics 6 (1992) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 89
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    Journal of Chemometrics 6 (1992), S. i 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 90
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 63-64 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 91
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 65-83 
    ISSN: 0886-9383
    Keywords: Trilinear decomposition ; Receptor modeling ; Source identification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In many cases, monitoring data for ambient airborne particles can be organized in the form of a three-way data table with one way for chemical species, one for sampling periods and one for sites. A direct trilinear decomposition followed by a matrix reconstruction (DTDMR) is developed to analyze such a data table as a whole. The three-way data set is composed into three two-way matrices by a direct trilinear decomposition (DTD). The column vectors of each of the matrices are called ‘source profiles’, ‘emission patterns’ and ‘site coefficients’ respectively. Particulate sources are identified by examining both their source profiles and emission patterns. After the sources have been identified, emission patterns and site coefficients are used to produce a three-way matrix that gives estimates of mass contributions of sources to the samples collected at every site in every period. By simulation study, not only has the method been verified, but a good indicator has been found that shows the number of factors (i.e. sources) in the system. Unlike other receptor models, DTDMR does not require source profile data and does not involve trial-and-error procedures. Since DTDMR identifies sources based on variations in two dimensions, it has a higher potential to distinguish two sources that have similar chemical compositions. The DTDMR model has provided excellent results with simulated data and has been applied in a real world three-way data set.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 92
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 113-116 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 93
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 117-118 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 94
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 151-161 
    ISSN: 0886-9383
    Keywords: NIR spectroscopy ; Wavelength selection ; Interaction effects ; Multicomponent mixtures ; Partial least squares ; Generalized least squares ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modern scanning (near-)infrared reflectance/absorption (NIR) spectroscopes measure the absorptions or reflectances at a sequence of around 1000 wavelengths. Training data may consist of 10-100 carefully designed sample mixtures for which the true composition of the mixture is either known by formulation or accurately determined by wet chemistry. In future one wishes to predict the true composition from the spectrum. In this paper we compare a simple wavelength selection approach with methods which retain all the wavelengths. It offers a powerful yet simple technique for choosing those wavelengths that are specific to each pure component as against the other components (including the medium) for the varying compositions. In the presence of a defined range of ingredients in thus chooses wavelengths which are highly selective for each particular component. It has the added advantage of selecting wavelengths which are little effected by interaction effects and consequent non-linearities.The calibration data used consist of 125 observations of three sugars, each varying at five levels in a full 53 design. The validation set consists of 21 further samples specially selected to have compositions outside the range of the training sample. The selection methods perform much better on this prediction set than methods which retain all the wavelengths, 700 in this case. The leave-one-out cross-validation internal to the calibration data would point to the opposite finding and suggests that such crossvalidations may be overly flattering to techniques such as partial least squares and may encourage overfitting. After selection, simple straightforward least squares methods may be used, eschewing the need for ‘shrinkage’ methods such as partial least squares or ridge regression.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 247-255 
    ISSN: 0886-9383
    Keywords: Analysis of variance ; Assumptions ; Graphics ; Models ; Validation of model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computer has made it possible to scrutinize data rapidly by means of graphics. This should be done prior to the application of any model to the data, since the model must be validated before using it as a means of analyzing the data. The procedure is illustrated in terms of two examples of real experimental data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 96
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 284-285 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 307-334 
    ISSN: 0886-9383
    Keywords: Non-linear PLS ; Quadratic regression ; Non-linear models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We treat here an extension of linear PLS regression to include regression on quadratic PLS components. The quadratic regression can be viewed as a natural extention of linear PLS regression to quadratic PLS according to the H-principle of mathematical modelling. The numerical implementation is treated in detail. It is shown that this approach can be used for models with large numbers of variables. Some modelling strategies are discussed depending on the purpose of the modelling. Applications of this approach are treated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 357-357 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 99
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 111-116 
    ISSN: 0887-3585
    Keywords: protein folding ; multiple minima problem ; peptide conformation ; energy calculation ; helices ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have investigated the conformational properties of a truncated analogue of mastoparan and of mastoparan X, both peptides from wasp venom. The electrostatically driven Monte Carlo method was used to explore the conformational space of these short peptides. The initial conformations used in this study, mainly random ones, led to α-helical conformations. The α-helical conformations thus found exhibit an amphipathic character. These results are in accord with experimental data from NMR and CD spectroscopy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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