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  • 1
    Electronic Resource
    Electronic Resource
    Hydrophobic organic micropollutants in samples of coastal waters: efficiencies of solid-phase extraction in the presence of humic substances (1998)
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 803-810 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid-phase extraction (SPE) has been used to enrich organic micropollutants (hydrophobic chlorinated and polycyclic aromatic hydrocarbons, CHC and PAH) from coastal water samples and to systematically study the influence of humic substances (HS) on SPE. A reversed phase (RP) system with high flow rates (rapid chromatography, RC) was used to show the basic adsorption principles and interaction processes which influence the enrichment of organic compounds. A model humic substance was found to hinder the enrichment of individual hydrophobic micropollutants (MP), depending on their octanol-water distribution coefficient P OW. This effect was found to be lower with natural humic substances. For longer contact time between water sample and adsorption material, the pollutant/humic substance bonding proved to be reversible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051019
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  • 2
    Electronic Resource
    Electronic Resource
    Electrothermal vaporization-ICP-MS for the determination of metals in micro amounts of high-purity non-metals (P, As, Sb, S, Se, Te, I) (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 520-526 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A thermal trace-matrix separation procedure has been developed for the determination of ultra-traces of metals in solid non-metals (P, As, Sb, S, Se, Te and I). These matrices are dissolved in high-purity hydrogen peroxide to form the corresponding acids. By applying a suitable temperature profile, coating the graphite tube with WC and using hydrogen as a gaseous modifier more than 90% of the matrix can be removed. Analyte recoveries are 90 to 105% with a standard deviation of 5 to 10%. Since the separation principle is not specific, non-metallic analytes show poor recoveries of 10 to 40% (20–100% RSD). Elements forming persistent carbides, such as refractory metals, require either HF or freon as an additional modifier. Separation of the matrix leads to higher sensitivities, fewer spectral and non-spectral interferences and to better precision. The graphite tube is only little contaminated and its lifetime is drastically increased. The improvements result in limits of detection in the lower pg/g-range in the solid non-metals. Furthermore, this method can be employed for amounts of sample around 1 mg at absolute detection limits below 1 pg. Best performance of the coupling of ETV to ICP-MS is only obtained in the single-ion monitoring mode which means only semi-sequential multi-element capabilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050752
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics and stoichiometry in the Karl Fischer solution (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 139-147 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mechanisms of the Karl Fischer (K.F.) reaction are reviewed and further investigated. Both kinetic measurements of the iodine concentration and chromatographic determinations of the reaction products were performed. In alcoholic solutions mainly alkyl sulfite is oxidized, and a reaction via partial formation of sulfur trioxide is proposed. In methanol an exact 1:1 stoichiometry (H2O:I2) has been verified. In the aprotic, dipolar solvents acetonitrile, DMF and propylene carbonate HSO3 –is oxidized by iodine. Based on formation and subsequent hydrolysis of base – SO3 adducts the stoichiometric factor for water is determined by type and concentration of the base, by the concentration of water and by the solvent itself. – In K.F. reagents the oxidation of SO2 by aerial oxygen to sulfate and alkyl sulfate takes place as a side reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000444
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of nitrophenols, nitrobenzoic acids and polar explosives by HPLC-diode array detection in ground water samples of former ammunition plants (1996)
    Springer
    Chromatographia 43 (1996), S. 612-618 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode array detection ; Explosives residues ; Nitro-compounds ; Ground water ; Ammunition waste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method with diode array detection for the determination of acidic aromatic nitro compounds (in particular nitrophenols and nitrobenzoic acids) in ground water around former ammunition plants is presented. The use of an isocratic mobile phase, buffered to a pH of 2.30 on a reversed phase column, allows the separation of several nitrophenols and nitrobenzoic acids, some of which are known as phototransformation products of 2,4,6-trinitrotoluene (TNT). In a ground water sample from the former ammunition site at Elsnig (Saxony, Germany) 2,4- and 3,5-dinitrophenol (18), picric acid (8) and 2,4-dinitrobenzoic acid (3) were identified in addition to a variety of explosives determined previously. The presence of these compounds was corroborated by a diode-array (DAD)-library search.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02292976
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  • 5
    Electronic Resource
    Electronic Resource
    Robustheit und Anfälligkeit als Kenngrößen zur Bewertung analytischer Systeme (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 319-324 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Robustness and Susceptibility as Descriptors for the Validation of Analytical SystemsThe use and meaning of robustness and similar terms well known but not defined in quality control and validation are discussed. Susceptibility is recommended as a numerical descriptor. Since limited errors of analytical signals can be tolerated and small deviations of method variables cannot be avoided susceptibility is defined as Ai,j=ΔSi,max/ΔVj, the maximum variation Δ of the analytical signal Si caused by a variation Δ of the system variable j on its level Vj. The need of rational discussion of and consensus on tolerable variations Δ is stressed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360408
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Ultraspuren-Analytik in hochreinem Phosphor mit thermischer Spuren-Matrix-Trennung durch ETV-ICP-MS (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 408-414 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ultratrace Analysis in High Purity Phosphorus by Thermal Trace-matrix-separation via ETV-ICP-MSElemental (red) phosphorus can be effectively volatilized and separated from ultra trace contaminants by electrothermal vaporization (ETV) in a graphite furnace. The tube must be covered with WC and some hydrogen added to the transport argon. Detection limits of 0,01 to 10 ng/g in the phosphorus sample are obtained for most analytes by ICP-MS in single ion monitoring mode. Exceptions are some carbide forming elements (B, Si, V), some contaminants from the graphite (B, Si) and some easily volatile traces (As, Sb, Te, I). ETV in multi element scan mode or alternatively wet chemical trace matrix separation (SMT) with an cation exchanger plus nebulizer aspiration allow detection limits about one order higher. The proposed technique requires a minimum of chemical manipulation and therefore reduces risk of contamination.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360505
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  • 7
    Electronic Resource
    Electronic Resource
    Expertensysteme zur Unterstützung der Analytischen Chemie: Verwechslungsprüfung und Schrott-Identifizierung in der Qualitätssicherung (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 458-464 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Expert Systems to Assist Analytical Chemistry: Confounding Tests and Scrap Identification in Industrial Quality ControlQuality control in the steel industry has to ensure the identity of semi-finished products and of scrap. This means to make a decision among about 2000 or more possibilities. The inductive learning algorithm ID3 is used to build the necessary decision tree, the main problem being overlap of the metal concentrations specifying the different alloys. Local attributes are introduced to split up remaining clusters without destroying the other parts of the tree. The system ist designed for use with industrial (mobile) spectrometers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360514
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  • 8
    Electronic Resource
    Electronic Resource
    Spuren-Matrix-Trennung als Probenvorbereitung für die Bestimmung von Chlorid, Bromid und Iodid durch Ionenchromatographie in Salzen, anderen Feststoffen und konzentrierten Lösungen (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 529-533 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trace-Matrix-Separation as Sample Pretreatment for the Determination of Chloride, Bromide and Iodide by Ion Chromatography in Salts, other Solid Samples and in Concentrated SolutionsChloride, bromide and iodide are collected from concentrated salt solutions on a column of Ag2CrO4. The excess of the collector is removed with acid and the silver halogenides dissolved with cyanide. The anions are separated on a PRP-X100 column using an eluent with p-hydroxybenzoic acid, p-hydroxobenzonitrile, methanol and cyanide. Detection limits are 0.2 ppm chloride, 0.04 ppm bromide and 0.2 ppm iodide, using conductivity detection and the Metrohm Ion Chromatograph 690.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701113
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  • 9
    Electronic Resource
    Electronic Resource
    Expertensysteme zur Unterstützung der analytischen Chemie: Intelligente Anwenderberatung für die ICP-Massenspektrometrie (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 16-22 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Expert Systems to Assist Analytical Chemistry: Intelligent User Counseling in ICP-Mass SpectrometryBecause ICP-mass spectrometry is a sensitive and rather new technique, some operators may lack the required thorough expertise. An intelligent system is presented which at first helps to identify any problems originating from the components of the actual sample. By demand of the user an experimental strategy to acquire any lacking information is provided. Based on this knowledge possible interferences are prognosticated. An appropriate operating procedure is then proposed, including suitable details of sample preparation. After the analytical measurement a scanned mass spectrum may be automatically checked for plausibility and for evidence of unexpected sources of error. The system is strictly organized in separated modules. It is open for easy introduction of additional knowledge and for the cooperation with the software of the spectrometer. The expert system shell Nexpert has been used as a building tool.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380103
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  • 10
    Electronic Resource
    Electronic Resource
    Expertensysteme zur Unterstützung der Analytischen Chemie: Realisierung von Lernfähigkeit und Plausibilitätsprüfung am Beispiel der ICP-Massenspektrometrie (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 593-597 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Expert Systems to Assist Analytical Chemistry: Realization of Learning Ability and Plausibility Checking Demonstrated for ICP Mass SpectrometryCertain, uncertain and lacking knowledge has to be considered for intelligent counseling. In the ICP mass spectrometry the composition of the actual sample and the ionization rates are the most important parameters to be prognosticated. The way of storage and retrieval of data and of decision making should be automatically checked and improved with respect to the success of previous guesses. The Dempster-Shafer theory is used for the combination and propagation of uncertainties.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199633801115
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