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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 55 (1992), S. 446-450 
    ISSN: 1432-0649
    Keywords: 41.60.Ap ; 41.85.-p ; 41.60.Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this note we explore the conditions under which synchrotron radiation can be used to trigger a photocathode gun. We show that such a solution offers in principle the possibility of operating with a pulsed electron beam filling all the buckets of the accelerating radio frequency. Some comments on the e-beam characteristics are also presented.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 23 (1987), S. 796-802 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Steroids ; Rat tissue ; Purification by extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method for analysis of steroids in the tissue of laboratory animals is described. A two-stage solid extraction procedure, utilizing Sep-pak C18 and graphitized carbon black, gives a purified product. Steroids in this extract were separated by multistep gradient elution with a reversedphase liquid chromatography system, using acetonitrilewater as solvent. Several columns with different geometry and phase loading were investigated. Optimum resolution was obtained with a medium covered and spherical particle. The applicability of this method was successfully demonstrated in the analysis of the testis and adrenal gland of rat.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Carbopack B ; Free sphingosine in human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid, sensitive and selective high-performance liquid chromatographic method has been developed for the determination of sphingosine in human serum. After precipitation with methanol, the samples were extracted using Carbopack B disposable columns; the sphingosine was eluted with 0.05 M hydrochloric acid in methanol-dichloromethane (20∶80, v/v) and the extract evaporated to dryness at 40°C. The sample residue was then reconstituted with methanol and reacted with o-phthaldialdehyde reagent to produce a fluorescent compound. Separation was performed using an LC-18 column with 0.05 M phosphate buffer (pH 7)-methanol-acetonitrile (15∶80∶5, v/v) as mobile phase. Fluorescence detection was performed with excitation and emission wavelengths of 340 and 455 nm, respectively. The serum extract was re-analyzed with a cyano LC column to minimize the possibility of false positive results. The possible interference of compounds having a structure similar to that of sphingosine was evaluated. The mean recovery of sphingosine was 〉94.5%. The limit of detection of the assay was 1 ng mL−1. The between-run and within-run coefficients of variation for replicate analyses were 〈4.0% and 〈3.4%, respectively. The levels of free sphingosine in the serum of 40 normal subjects (20 male and 20 female) was investigated; the average level was 81.6±41.1 ng mL−1 (mean ±S.D.) for males and 85.5±33.7 ng mL−1 for females.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 38 (1994), S. 88-92 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenylurea herbicides ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method has been developed for the determination of thirteen phenylurea herbicide residues in milk. It involves one-step solvent extraction of the milk with methanol by ultrasonication. The extract is cleaned up on an Amberchrom resin cartridge. Reversed-phase, gradient elution, high-performance liquid chromatography with UV detection at 242 nm is used to analyse the residues. The recovery of thirteen phenylurea pesticides is quantitative, ranging from 71.4% to 97.9% for the individual herbicides investigated at concentrations around 0.05 mg kg−1 and from 65.1% to 95.6% around 0.005 mg kg−1. The method is not associated with any of the emulsion problems common to conventional solvent extraction, which considerably reduce the sample clean-up process compared with existing methods.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 41 (1995), S. 178-182 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid-phase extraction ; Triazine herbicides ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatography with UV detection was used to determine eight triazine herbicides in milk. Solid-phase extraction was performed using a double trap; first, a nonspecific adsorbent (Carbograph), and then a cation exchanger (SCX). Eluate from the SCX was evaporated to dryness under reduced pressure and redissolved in mobile phase. An aliquot was injected into the chromatography, which was operated isocratically in the reverse-phase mode with UV detection at 225 nm. Analytical recoveries for the eight triazines ranged from 73.0% to 92.4%. The limit of sensitivity of this method was about 0.09 ng mL−1 of milk. The method was validated and evaluated by comparison with a method reported in literature.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; MS detection ; Trace herbicides ; Natural waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the simultaneous identification and quantification of base/neutral and acidic pesticides at a low nanogram per liter concentration level in natural waters is presented. The method includes enrichment of the compounds by solid phase extraction on graphitized carbon black, followed by sequential elution of the base/neutral and acidic pesticides. Identification and quantification of the compounds is performed with HPLC-ESI-MS. This procedure involves passing 1 L of ground water and 2 L of drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mm-i.d. reversed phase LC C-18 operating with a 1 mL min−1 flow of the mobile phase was used to chromatograph the analytes. A flow of 100 μL min−1 of the column effluent was diverted to the ESI source. The ESI source was operated in positive ion mode for base/neutral pesticides and in negative-ion mode for acid pesticides. For the analyte considered, the response of the mass detector was linearly related to the amount of the analytes injected between 5 and 250 ng. In all cases, recoveries of the analytes were better than 90%. The limit of detection (signal-to-noise ratio=3) of the method for the pesticides considered in drinking water samples was estimated to be about 3–10 ng L−1.
    Type of Medium: Electronic Resource
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