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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 [...]

Chemistry Paper Abstracts ALGORITHMS FOR REMOVING DRIFT IN MICROBALANCE READINGS. HALEY D. ALBRIGHT, M. B. MOELLER, DEPT. OF CHEMISTRY AND INDUSTRIAL HYGIENE, AND P. G. DAVISON, DEPT. OF BIOLOGY, UNIVERSITY [...]

Characterization of the chemical composition and chemical transformations of secondary organic aerosol (SOA) is both a major challenge and the area of greatest uncertainty in current aerosol research. This study presents the first application of desorption electrospray ionization combined with high-resolution mass spectrometry (DESI-MS) for detailed chemical characterizaton and studies of chemical aging of organic aerosol (OA) samples collected on Teflon substrates. DESIMS offers unique advantages both for detailed characterization of chemically labile components in OA that cannot be detected using traditional electrospray ionization mass spectrometry (ESI-MS) and for studying chemical aging of OA. DESI-MS enables rapid characterization of OA samples collected on substrates by eliminating the sample preparation stage. In addition, it enables detection and structural characterization of chemically labile molecules in OA samples by minimizing the residence time of analyte in the solvent. In this study, DESIMS and tandem mass spectrometry experiments (MS/MS) were used to examine chemical aging of SOA produced by the ozonolysis of limonene (LSOA) in the presence of gaseous ammonia. Exposure of LSOA to ammonia resulted in measurable changes in the optical properties of the sample observed using ultraviolet (UV)-visible spectroscopy. High-resolution DESI-MS analysis demonstrated that chemical aging results in formation of highly conjugated nitrogen-containing species that are most likely responsible for light-absorbing properties of the aged LSOA. Detailed analysis of the experimental dam--allowed us to identify several key aging reactions, including the transformation of cardonyls to imines, intramolecular dimerization of imines with other carbonyl compounds in SOA, and intermolecular cyclization of imines. This study presents an important step toward understanding the formation of light-absorbing OA (brown carbon) in the atmosphere. 10.1021/ac902801f

An in-house-built ion trap mass spectrometer combined with a soft ionization source has been set up and tested. As ionization source, an electron beam pumped vacuum UV (VUV) excimer lamp (EBEL) was used for single-photon ionization. It was shown that soft ionization allows the reduction of fragmentation of the target analytes and the suppression of most matrix components. Therefore, the combination of photon ionization with the tandem mass spectrometry (MS/MS) capability of an ion trap yields a powerful tool for molecular ion peak detection and identification of organic trace compounds in complex matrixes. This setup was successfully tested for two different applications. The first one is the detection of security-relevant substances like explosives, narcotics, and chemical warfare agents. One test substance from each of these groups was chosen and detected successfully with single photon ionization ion trap mass spectrometry (SPI-ITMS) MS/MS measurements. Additionally, first tests were performed, demonstrating that this method is not influenced by matrix compounds. The second field of application is the detection of process gases. Here, exhaust gas from coffee roasting was analyzed in real time, and some of its compounds were identified using MS/ MS studies.

Electrospray-assisted laser desorption/ionization (ELDI), an ionization method that combines laser desorption and electrospray ionization (ESI), can be used under ambient conditions to characterize organic compounds (including FD&C dyes, amines, extracts of a drug tablet) separated in the central track on a thin-layer chromatography (TLC) plate coated with either reversed-phase [C.sub.18] particles or normal-phase silica gel. After drying, the TLC plate was placed on an acrylic sample holder set in front of the sampling skimmer of an ion trap mass analyzer. The chemicals at the center of the TLC plate were analyzed by pushing the sample holder into the path of a laser beam with a syringe pump. The molecules in the sample spot were desorbed by continuously irradiating the surface of the TLC plate with a pulsed nitrogen laser. Then, the desorbed sample molecules entered an ESI plume where they were ionized through the reactions with the charged species (including protons, hydronium ions and their cluster ions, solvent ions, and charged droplets) generated by electrospraying a methanol/water solution. MS/MS analyses were also performed to further characterize the analytes. The detection limit of TLC/ELDI/MS is ~ [10.sup.6] M. This was evaluated by using FD&C red dye as the standard. A linear relationship was found for the calibration curve with the concentration of FD&C red dye ranged from [10.sup.-3] to [10.sup.--6] M.

A novel chemiresistor sensor for detection of organic analytes in high-conductivity aqueous electrolyte solution is reported. The chemiresistor sensor is based on thin films of gold nanoparticles capped with a 1-hexanethiol monolayer that is inkjet printed onto a microelectrode. In order for a change in nanoparticle film resistance to be measured, the electronic conduction must preferentially occur through the nanoparticle film rather than through the high-conductivity electrolyte solution. This was achieved by miniaturizing the chemiresistor device such that the double layer capacitance of the electrodes in contact with the electrolyte solution gives rise to a significantly larger impedance compared to the nanoparticle film resistance. This system was shown to be sensitive to simple organics dissolved in an aqueous electrolyte solution. The organic analytes, dissolved in the aqueous solution, partition into the hydrophobic nanoparticle film causing the nanoparticle film to swell, resulting in an increase in the low-frequency impedance of the sensor. An increase in the impedance, at 1 Hz, of the gold nanoparticle chemiresistor on exposure to toluene, dichloromethane, and ethanol dissolved in 1 M KCl solution was demonstrated with detection limits of 0.1, 10, and 3000 ppm, respectively. Titration curves over 3 orders of magnitude could be obtained for analytes such as toluene.

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

Organic molecules in comets, meteorites and the interstellar medium are discussed with attention to gas phase and grain surface formation pathways in dense interstellar clouds. The most important spectroscopic evidence in the diffuse interstellar medium is reviewed. Signatures and unsolved problems related to the main organic components thought to be present in the diffuse gas are criticized and circumstellar formation of organics around late-type stars considered. Recent observations with the Infrared Space Observatory and ground-based radiotelescopes have been important in this field.

A new experiment for introductory organic chemistry laboratory courses relies on the use of modern spectroscopic tools for the most part and incorporates organic name reactions, omitting qualitative analysis, in identification of an unknown. The experiment is intended to more accurately reflect circumstances encountered by an organic chemist trying to identify a compound. The conventional approach in an unknown-identification lab is messy, chaotic, produces a variety of wastes, and is unrealistic, even with microscale experiments.

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

A method for presenting functional groups in a more systematic way is presented. The method of classification presented allows students to develop a solid basis in their study of organic chemistry.

The 1832 paper by German Justus von Liebig and Friedrich Wohler is attributed with the first use of melting points as a means of characterizing organic compounds. The popularity of the determination of melting points began in the 1870s and laboratories were already selling instruments for this purpose by 1900.