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The limit of detection of gas chromatography-electron ionization mass spectrometry (in scanning in the full ion current mode) is 10.sup.-11 to 10.sup.-10 g, depending on the substance. A full electron ionization mass spectrum of a substance can be recorded for 10.sup.-10 to 10.sup.-9 g, while the peak of the molecular ion in these mass spectra is often either absent or of low intensity. The minimum amount of a substance that can be detected by gas chromatography-atmospheric pressure photoionization mass spectrometry is 10.sup.-12 to 10.sup.-10 g and by gas chromatography-atmospheric pressure photochemical ionization mass spectrometry is 10.sup.-14 to 10.sup.-12 g, depending on the analyte and the reagent substance. For the amount of substance in the range from 10.sup.-9 to 10.sup.-10 g and up to the limit of detection, a mass spectrum consisting of the peaks of the M.sup.+ [Formula omitted] or MH.sup.+ ion or both of them is recorded. It gives selective information about the molecular weight of the analyte throughout the studied range. Identifying trace amounts of unknown components in complex mixtures can be achieved by sharing data from the mass spectra of electron ionization and atmospheric pressure photoionization., Author(s): I. A. Revelsky [sup.1] , Yu. S. Yashin [sup.1] , A. S. Samokhin [sup.1] , A. I. Revelsky [sup.1] Author Affiliations: (1) https://ror.org/010pmpe69, grid.14476.30, 0000 0001 2342 9668, Department [...]

Four types of reactions (azo coupling, protolytic and oxidative condensation, ion association), accompanied by the formation of hydrophobic colored analytical forms of corresponding organic analytes, are proposed on an example of biologically active substances (aromatic amines, [alpha]-amino acids, antibiotics of aminoglycoside and [beta]-lactam series, anionic surfactants). It is shown that, in these systems, the hydrophobicity of both the initial reactants, e.g., tetrafluoroborates of diazonium salts, and analytical forms (azo compounds, Schiff bases, Ruemann's purpura, ion associates with surfactants) can be increased. Possibilities of various methods for the derivatization of organic analytes with the formation of colored analytical forms with increased hydrophobicity for the best fixation on solid matrices and the development of test systems on their basis, which can be used to control the quality of various samples with rather good performance characteristics, are considered., Author(s): T. A. Sokolova [sup.1] , I. V. Kosyreva [sup.1] , S. Yu. Doronin [sup.1] Author Affiliations: (1) Chernyshevsky Saratov National Research State University, , 410012, Saratov, Russia Biologically active [...]

A mathematical model is proposed for revealing the absence of a compound to be identified in an electron impact mass spectral library. The mathematical model (developed based on PLS Discriminant Analysis) can be represented as a 'black box' which provides an answer whether a compound to be sought is absent or present in a database. The match factors of top ten candidates among the possible ones were used as input data. More than 5000 objects (mass spectra) were used at the steps of training, validation, and testing. The developed classification model provides correct prediction (of whether a compound is absent from the library) in 28.4% cases, while only 1.2% of compounds present in the database were incorrectly classified as the absent ones. Keywords: identification of organic compounds, GC/MS, mass spectral library, mass spectral database, classification, PLS discriminant analysis DOI: 10.1134/S1061934817140143, INTRODUCTION Combined gas chromatography--mass spectrometry (GC/MS) is one of the most widely used methods for the trace determination of organic compounds in samples of complex composition. The possibilities of this [...]

Abstract: It is found that the interaction of retinol, ergocalciferol, and cholecalciferol with electrochemically generated bromine proceeds rapidly and quantitatively. The stoichiometric coefficients of the reaction are 1 : 2, 1 : 7, and 1 : 3, respectively. A coulometric determination of microgram amounts of individual liposoluble antioxidants in model solutions was performed with RSD = 1--5%. The voltammetric response of retinol and [alpha]-tocopherol was studied at a stationary platinum microelectrode in 0.1 M HClO.sub.4 and 0.1 M C[H.sub.3]COONa in acetonitrile. The quantification limit for [alpha]-tocopherol is 2.7 x 10.sup.--4 M in 0.1 M HClO.sub.4, and the quantification limits for retinol are 4.1 x 10.sup.--5 M in 0.1 M HClO.sub.4 and 2.1 x 10.sup.--5 M in 0.1 M C[H.sub.3]COONa. A procedure for the coulometric determination of total free liposoluble antioxidants in human blood serum is proposed. Article History: Registration Date: 07/10/2004

Byline: Yu. F. Milyaev (1), E. V. Semenova (1) Abstract: It was shown that mezapam can be determined by cathodic stripping voltammetry in aqueous media. At a potential sweep rate of 50 mV/s, pH 2.5, amplitude of polarizing voltage of 50 mV, initial accumulation potential of --0.75 V, and accumulation time of 1 min, the detection limit for mezapam was found to be 0.1 ug. Author Affiliation: (1) Department of Organic Substance Production, Novomoskovsk Institute of Mendeleev University of Chemical Engineering, ul. Druzhby 8, Novomoskovsk, Tul'skaya oblast, 301650, Russia Article History: Registration Date: 06/10/2004

Byline: I. N. Stan'kov (1), A. A. Sergeeva (1), V. B. Sitnikov (1), I. D. Derevyagina (1), O. T. Morozova (1), S. N. Mylova (1), V. B. Forov (1) Abstract: A gas chromatographic procedure is developed for the determination of [beta],[beta]-dichlorodiethylsulfide (yperite, sulfur mustard) and [beta]-chlorovinyldichloroarsine (lewisite) in the working area and community air at a level defined by the hygienic regulations for community air (2 x 10.sup.--6 and 4 x 10.sup.--6 mg/m.sup.3 for sulfur mustard and lewisite, respectively) and at the maximum permissible level for a working area (2 x 10.sup.--4 mg/m.sup.3). The procedure for the determination of sulfur mustard is based on the trapping of the analyte from air with Silochrom S-120 impregnated with Apiezon L with further extraction by a 1 : 1 acetone--hexane mixture, the evaporation of the extract to a small residual volume, and chromatography with an electron capture detector. The procedure for the determination of [beta]-chlorovinyldichloroarsine (lewisite) involves the absorption of the analyte with a 2.2% solution of triethanolamine in 0.1 M hydrochloric acid, the conversion of lewisite to acetylene by treating the trap contents with 30% alkali solution, and the chromatography of the vapor phase using a flame ionization detector. The error of the determination is no more than +-23 rel %. The analysis takes 1.5 h. Author Affiliation: (1) Russian Research Institute of Organic Chemistry and Technology, sh. Entuziastov 23, Moscow, 111024, Russia Article History: Registration Date: 06/10/2004

Byline: E. V. Alekseev (1), L. A. Gribov (1), S. G. Ivanov (1) Abstract: Density functional theory can be used in the quantitative analysis of substances by their IR spectra in cases when high precision is not necessary or certified reference samples are principally unavailable or are difficult to obtain. IR spectra of 30 complex organic molecules including different heteroatoms (Br, Cl, F, N, O) were calculated using the Gaussian98w program (6-31G) basis set. The calculated spectra were compared with experimental ones, and quantitative inverse spectral problems (calculation of concentrations) were solved for all of the molecules studied. It was shown that the found concentrations for the majority of the studied substances differ from their true concentrations by no more than 30%, which is acceptable, for example, for ecological monitoring. Author Affiliation: (1) Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia Article History: Registration Date: 06/10/2004

Byline: L. F. Naumenko (1), N. M. Buneeva (2), R. N. Korneeva (2), V. F. Selemenev (2), D. V. Nemtsev (3) Abstract: A simple and rapid procedure was developed for the potentiometric titration of citrate ions in fermented solutions from citric acid production with the use of a copper-selective electrode. Author Affiliation: (1) Department of Chemistry, Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006, Russia (2) Voronezh State Agrarian University, ul. Michurina 1, Voronezh, 394087, Russia (3) Belgorod Citric Acid Production Plant, ul. Chicherina 8, Belgorod, 308015, Russia Article History: Registration Date: 06/10/2004

Byline: Farzaneh. Shemirani (1), Masood. Salavati Niasari (2) Abstract: A method for the preconcentration of Cd(II), Cu(II), Zn(II), and Ni(II) is proposed using a minicolumn filled with silica gel modified by Schiff's base. The retained analytes on the ligand-coated silica gel were recovered with a small volume of HNO.sub.3 (nitric acid). The metal ions in the eluent were determined by flame atomic absorption spectrometer (FAAS). Different factors, including the pH of the sample solution, the sample volume, the amount of silica gel, eluent volume and matrix effects for preconcentration were examined. The recoveries for the analytes under optimum working conditions were higher than 95%. The relative standard deviations of the determination were 1.50, 2.10, 2.40, 3.43% for Cu(II), Cd(II), Zn(II) and Ni(II). The limits of detection (3s, n = 10) for Cd(II), Cu(II), Zn(II), and Ni(II) were found to be 3, 5, 5 and 4.7 ngL.sup.--1. The proposed method was applied to the analysis of some natural water samples and standard reference aluminum alloy material (NBS SRM 85b). Author Affiliation: (1) Department of chemistry, Faculty of Science, University of Tehran, IRAN (2) Department of chemistry, Faculty of Science, University of Kashan, IRAN Article History: Registration Date: 06/10/2004

Byline: V. V. Kuznetsov (1), Yu. V. Ermolenko (1), A. Ya. Zheltov (1), K. A. Kornev (1), S. V. Sheremet'ev (1) Abstract: The coprecipitation of azo compounds based on 4-nitrophenyl- and 4-sulfophenyldiazonium naphthol sulfonates as their diphenylguanidinium ion-pair complexes with analogous compounds of naphthalene-2-sulfonic acid and 4-phenylsulfodiazonium is investigated. The optimization of the coprecipitation is considered based on the notions of the driving force of the cocrystallization of impurities. The optical characteristics of colored ion-pair complexes are measured. It is found that the water solubility is decreased most substantially for azosulfonates with hydrophobic nitro groups and with no more than two sulfo groups in different aromatic nuclei, which can lead to a decrease in the detection limit due to preconcentration by coprecipitation, which stimulates the thermodynamic flux of concentrate elution. Coprecipitation is combined with flow-injection analysis in the on-line mode, and new procedures are developed for determining naphthol sulfonates and related azo compounds with the detection limit equal to 0.003--0.006 mg/50 mL. Author Affiliation: (1) Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125047, Russia Article History: Registration Date: 06/10/2004

Byline: E. A. Illarionova (1), I. P. Syrovatskii (1), E. M. Artasyuk (1) Abstract: A unified procedure was developed for the spectrophotometric determination of pyrazidole in the medicinal substance and in tablets using phenolphthalein or benzoic acid as reference samples. The best conditions for the determination have been found as follows: 0.1 M HCl as a solvent and an analytical wavelength of 276 nm. The scaling factors have been determined. Calibration equations are given. The relative standard deviations of the results obtained with the proposed procedure are less than 0.5% for the substance and 3.3% for tablets. Author Affiliation: (1) Department of Pharmacy, Irkutsk State Medical University, Irkutsk, 664003, Russia Article History: Registration Date: 06/10/2004

Byline: U. Hener (1), W. A. Brand (2), A. W. Hilkert (2), D. Juchelka (1), A. Mosandl (1), F. Podebrad (1) Keywords: Key wordsaGC-pyrolysis-IRMS; GC-combustion-IRMS; [delta]18O values; [delta]13C values; Vanillin; 13C analysis; 18O analysis; Multi-element analysis Abstract: aThe on-line coupling of gas chromatography and isotope ratio mass spectrometry via a pyrolysis interface (GC-pyrolysis-IRMS, GC-P-IRMS) allows the simultaneous determination of [delt[a].sup.13]C and [delt[a].sup.18]O values for organic compounds. On the basis of illustrative investigations of vanillin from different origins, the scope and limitations of the new method are discussed. Author Affiliation: (1) Johann Wolfgang Goethe-Universitat Frankfurt, Institut fur Lebensmittelchemie, Marie-Curie-Strasse 9, D-60439 Frankfurt, Germany, DE (2) Finnigan MAT, Barkhausenstrasse 2, D-28197 Bremen, Germany, DE Article note: Received: 18 October 1997 / Revised version: 18 December 1997