Micro and trace determination of oxygen in organic compounds

Samples are pyrolyzed over carbon in helium doped with chloropentane, which enhances the liberation of the oxygen. The carbon monoxide formed is determined by gas chromatography. A modification of a Carlo Erba CHN+O Elemental Analyzer is described, and results of micro and trace determinations in organic and inorganic compounds are reported. Basic reactions in this method for oxygen determination are discussed.     

Correlation of trace element content in air particulates with solar meteorological data in the atmosphere of Athens

In this paper, the relation between the trace element content in air particulates and solar meteorological data in the atmospheric environment of Athens, Greece, was studied. For this purpose, Sm, Br, As, Na, K, La, Ce, Cr, Ag, Sc, Fe, Zn, Co, Sb, Th were determined by INAA in respirable aerosols collected during winter 1993-1994. The results showed that the average cloudiness, sunshine, and the total solar radiation (sun and sky) on a horizontal surface, (3 variables) have no relation with trace element variation. However, diffuse solar radiation (sun and sky) on a horizontal surface seems to have statistically significant relationship with some of the trace element variation. It forms a single component with some trace elements after the application of the factor analysis. The increase of the same solar variable in the Athens City center, is one of the factors which cannot permit the emission of trace elements in the atmospheric environment from dust soil and car tires.     

New methodologies in trace analysis of volatile organic compounds

Two methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 μm) of cross-linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices. The second technique is based on chromatographic evaporation of a solvent in a capillary tube, where the process is sustained by a repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc.     

热脱附-吹扫捕集-气相色谱质谱联用在大气挥发性有机物分析中的应用探索

采用热脱附结合吹扫捕集(P&T)技术对大气中挥发性有机物(VOCs)进行富集,并用气相色谱质谱(GC/MS)进行分析检测,建立了一种大气中多组分VOCs分析方法。将热脱附-吹扫捕集-气相色谱质谱联用技术应用于大气挥发性有机物分析中,使样品经过吸附管及捕集阱双重富集后再进入GC/MS检测,VOCs分析结果部分目标物检出限可达到0.1 ng/L,实际平行样品检测结果相对偏差小于30%,且可同时对54种VOCs进行定性定量分析。     

Automated measurement and calibration of reactive volatile halogenated organic compounds in the atmosphere

The automated calibration and analysis of very low mixing ratios of the reactive volatile organic halocarbons CH(3)I, CHCl(3), C(2)H(5)I, 2-C(3)H(7)I, CH(2)Br(2), CH(2)ClI, CHBr(2)Cl, 1-C(3)H(7)I, CH(2)BrI, CHBr(3) and CH(2)I(2) for long term atmospheric field measurements are described. Analytes were pre-concentrated from 3 l of air onto an adsorbent trap cooled to -10 [degree]C using Peltier plates, and rapidly transferred to a gas chromatograph (GC) by resistive heating. A two stage Carboxen 1016/Carbotrap C adsorbent trap allowed good analyte recovery and rapid desorption without the need for post-desorption cryofocussing. Halocarbons were detected using a mass spectrometer (MS) in selective ion mode. Detection limits were between 0.02 and 0.12 pptv (parts per trillion by volume) for approximately hourly samples of CHCl(3), CH(3)I, C(2)H(5)I, 1-C(3)H(7)I, 2-C(3)H(7)I, CH(2)ClI, CH(2)Br(2), CHBr(2)Cl, CH(2)BrI, CHBr(3) and CH(2)I(2) with a precision of 3-8%. A novel calibration system was constructed which utilised fixed volume (50 [micro sign]l) injections of the output of thermostatted permeation tubes into a stream of nitrogen gas in order to dilute parts per million by volume (ppmv) mixing ratios into pptv. The calibration was completely automated, allowing multi-point calibrations during routine operation. The overall accuracy of the measurements is estimated to be +/-15%. The instrument was used continuously for automated atmospheric measurements during a 4-month research cruise from Germany to Antarctica, and a 6 week field campaign at Mace Head, Ireland. The results for CHCl(3) during the latter campaign were within 13% of measurements made by a GC-MS operating continuously at the site within the long term Advanced Global Atmospherics Gases Experiment.     

Direct thermal desorption of semivolatile organic compounds from diffusion denuders and gas chromatographic analysis for trace concentration measurement

A novel method for collection and analysis of vapor-phase semivolatile organic compounds (SOCs) in ambient air is presented. The method utilizes thermal desorption of SOCs trapped in diffusion denuders coupled with cryogenic preconcentration on Tenax-TA and analysis by high resolution gas chromatography (GC)-electron-capture detection (ECD). The sampling and analysis methods employ custom-fabricated multicapillary diffusion denuders, a hot gas spike (HGS) apparatus to load known quantities of thermally stable standards into diffusion denuders prior to sample collection, a custom-fabricated oven to thermally desorb SOCs from the diffusion denuder, and a programmable temperature vaporization (PTV) inlet containing a liner packed with Tenax-TA for effective preconcentration of the analytes and water management. High flow rates into the PTV inlet of 750mLmin(-1)during thermal desorption are ca. a factor of ten greater than typically used. To improve resolution and retention time stability, the thermal desorption and PTV inlet programming procedure includes three steps to prevent water from entering the analytic column while effectively transferring the analytes into the GC system. The instrumentation and procedures provide virtually complete and consistent transfer of analytes collected from ambient air into the GC evidenced by recovery of seven replicates of four internal standards of 90.7+/-4.0-120+/-23% (mean+/-95% confidence interval, CI). Retention time based compound identification is facilitated by low retention time variability with an average 95% CI of 0.024min for sixteen replicates of eight standards. Procedure details and performance metrics as well as ambient sampling results are presented.     

Aerosol-OT-gamma-alumina admicelles for the concentration of hydrophobic organic compounds in water

A novel admicelle composing of a dialkylated anionic surfactant, di-2-ethylhexyl sodium sulfosuccinate (Aerosol-OT, AOT) and gamma-alumina was prepared by mixing them in acidic aqueous solution. The amount of the maximum sorption of AOT on 1 g of alumina at pH 2 was ca. 130 mg. By comparing the fluorescence spectra of N-phenyl-1-naphthylamine in different solvents, the solvent property of AOT-gamma-alumina admicelles was corresponding to that of toluene or diethyl ether. Thus, the AOT-gamma-alumina admicelles had greater hydrophobicity than SDS-gamma-alumina admicelles having similar hydrophobicity to 1-octanol or ethyl acetate. Hydrophobic organic compounds, chlorophenols having more than three chloro substituents, octylphenol, nonylphenol, dibutyl phthalate was almost quantitatively (98% or more) collected onto AOT admicelles composing of 1.5 g gamma-alumina and 150 mg AOT. The greater collection yields rather than those in SDS-admicellar system were ascribable to greater hydrophobicity and stability of AOT admicelles. After the 500-fold concentration, traces (nM) of organic contaminants in water samples were successfully detected with an HPLC having a photometric detector.     

Correlation steam/solid chromatography of trace organic compounds in water

Correlation steam/solid chromatography is used for direct determinations of traces of organic compounds in water. Because of suppression of detector noise, correlation chromatography is a practical alternative to single injections or sample concentration at low μg l^?1 levels.     

Survey of reference materials for trace elements, nuclides and organic microcontaminants

The International Atomic Energy Agency (IAEA), in co-operation with the United Nations Environment Programme (UNEP), has recently prepared a survey on internationally available analytical reference materials for trace elements, nuclides and organic contaminants in biological, environmental and related matrices. The purpose is to help analysts to select reference materials for quality assurance that match as closely as possible, with respect to matrix type and concentrations of the measurands of interest, the “real” samples that are to be measured. The present version of the survey, which is available in the form of two cost-free printed volumes [1], contains over 10,000 certified and information values in 650 reference materials from 27 different producers. The 455 measurands listed include trace elements, major and minor elements, organic contaminants, organometallic compounds, radionuclides and stable isotopes. Currently, the database from which the survey has been produced is being modified and extended so as to make the data available in electronic form via the Internet. Received: 11 June 1997 / Revised: 7 July 1997 / Accepted: 9 July 1997     

New thermochemical reference system expressing the relative energy of organic compounds

To facilitate the comparison of the energies of nonisomeric organic compounds, we introduce a new thermochemical reference system. The reference substances, instead of elements, are series of compounds: unbranched alkanes and their selected derivatives (halogenides, ethers, sulfides, and tertiary amines). The relative enthalpies calculated from the heats of formation directly reflect the relative energy of both isomeric and nonisomeric compounds, and they can be used in the calculation of the heats of reaction. The relative enthalpies of the elements (in kJ/mol) are C, –22.846; H₂, 43.426; O₂, 251.66; N₂, –178.62; S, –41.62; F₂, 396.12; C1₂, 94.22; Br₂, 8.16; and I₂, –107.64.     

Determination of trace amounts of phosphorus in organic compounds by wickbold combustion

Summary Wickbold combustion in a standard quartz apparatus with a suction burner is suitable for phosphorus determination in acetonesoluble materials if the samples are burned together with an organic halide, e. g. carbon tetrachloride. Probably phosphorus halides are formed which pass through the hot parts of the apparatus fast enough not to react with the quartz walls. The recovery is 95–100% for amounts of phosphorus up to 3.5 mg per combustion.

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Bestimmung von Phosphorspuren in organischen Verbindungen durch Wickbold-Verbrennung

Zusammenfassung Die Wickbold-Verbrennung in einer normalen Quarz-Apparatur mit Saugbrenner ist zur Phosphor-Bestimmung in acetonlöslichen Substanzen geeignet, wenn gleichzeitig mit den Proben eine organische Halogen-Verbindung, z. B. Tetrachlorkohlenstoff, verbrannt wird. Vermutlich werden dabei Phosphorhalogenide gebildet, die die heißen Zonen der Apparatur so schnell passieren, daß keine Reaktion mit den Quarzwänden stattfindet. Die Wiederfindungsrate für Phosphormengen bis 3,5 mg pro Verbrennung beträgt 95–100%.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

A calculation method to estimate the concentration and elemental composition of organic substances in natural Waters

The possibility of calculating the elemental composition and concentrations of organic substances in natural water based on the results of determining organic carbon and nitrogen and chemical oxygen demand is substantiated both theoretically and experimentally. Three types of substances differing in the electrochemical valence of carbon were among organic substances. The elemental composition of a number of water objects was analyzed. It was found that the concentrations of organic carbon, oxygen, hydrogen, and nitrogen are close to 50, 40, 4–5, and 2–5%, respectively.     

Determination of traces of organic compounds in the atmosphere: role of detectors in gas chromatography

The degree of toxicity of organic compounds is often related to molecular structure, not necessarily to class of compound, so that reliable air-quality monitoring requires selective, sensitive detection of traces of specific compounds, usually in complex mixtures in the atmosphere. Gas chromatography offers the major approach to such analyses. Responses of flame ionization, electron capture and thermionic detectors to types of structures and compounds are discussed. Relative sensitivity data and retention times are given for 34 organic compounds: substituted nitrobenzenes, benzonitriles, benzaldehydes, anisoles, toluenes, xylenes and acetophenones.     

Ionization energies of homologous organic compounds and correlation with molecular size

The empirical relationship IE ∝? 1/n, between the ionization energy (IE) and molecular size (as represented by the number of atoms, n) in homologous series of organic compounds has been confirmed for n-alkanes, alkyl halides, cyclic ethers and alkyl-subsiituted cycloalkanes. For each series, the plot of IE vs. 1/n produces a line of characteristic slope. The only exception is the cycloalkanes themselves, whose IE values (from C₃ to C₈) are closely similar. The possible relationship between the IE, the polarizability of the molecules and the energy of the highest occupied molecular orbital is briefly discussed.     

Determinations of uranium at trace and subtrace levels in organic substances by wet ashing-Arsenazo III method

A method was developed for the determination of trace and subtrace amounts of uranium in organic substances used during the industrial process of nuclear fuel production. The method is based on decomposing 50 g of the sample by wet ashing with 25 g conc. sulfuric acid. The residue from the ashing process was ignited at 525 °C to remove all carbonaceous materials. The residue was boiled with 10 ml of 11 nitric acid. The resulting solutions was analyzed for uranium concentration using a modification of the arsenazo III method which allows for uranium determination after separating it by TBP extraction from all the interfering elements. The proposed method proved to be sensitive (detection limit: 15 ppb). The relative standard deviation of the method for a sample containing 200 ppb uranium is 5%. The dynamic range of the method is wide, since the method is applicable. for trace and subtrace levels of uranium in organic substances.     

Hybrid NAA method for assessment of the levels of organic halogen compounds in the atmosphere in China

Abstract Passive air samplers (polyurethane foam disks) were deployed at 25 urban sites and 66 rural sites over the period of July to October 2005, partly between October 2005 and January 2006 for about 120 days across China, and analyzed for extractable organo-chlorine /-bromine /-iodine (EOCl/EOBr/EOI) and polychlorinated biphenyls (PCBs) using hybrid neutron activation analysis (NAA) combined with gas chromatographymass spectrometry (GC-MS). The average concentration of EOCl, EOBr, EOI and ΣPCBs among all the sites were 173.7, 3.5, 1.0 and 0.74 ng/d, respectively. Higher values of EOCl/Br/I and PCBs were detected in the areas of high usage and high emission, which were linked to relatively high-income areas in China, while lower in the west ill-developed region of China, which indicated that these pollutants mainly came from industrial pollution. Higher EOCl contents in traffic areas stated that the exhaust emission from vehicle was another main source of organochlorines in the air. The relative proportions of the known organochlorines (84 PCB congeners) to total EOCl were 0.02–3.0%, which implied that most of EOCl measured in air were unknown.     

C4-C14-alkyl nitrates as organic trace compounds in air

The long chain alkyl nitrates (C _n >5) form a complex spectrum of natural and anthropogenic organic trace compounds in air. HRGC/ECD and HRGC/MSD using 56 amu as the signal reveal a standard pattern of isomeric n-alkyl nitrates in semi-rural air. This is regulated by the input of the corresponding alkanes, their rate constants for the reaction with OH, the rate constant of the alkylperoxy radicals for the reaction to alkyl nitrates, the atmospheric concentrations of NO/NO₂ and by the rate constants of the alkyl nitrates for the reaction with OH radicals as the major removal reaction. The complex pattern of signals given by the ECD in the retention index range between 700 and 2000 has been observed before but this is the first time that it has been assigned to a defined group of chemical compounds.The environmental impact of the occurrence of the different groups of alkyl nitrates has yet to be evaluated. Their general property as organic stabilizers for NO/NO₂ and therefore as precursors of NO ₃ ^- ions in rain and their biological potentials are also known. The long chain alkyl nitrates act as lipophilic carriers for nitric acid.