B.V. Ioffe

Volatile organic compounds in the atmosphere of forests

Abstract The procedure of sampling and gas chromatographic-mass spectrometric analysis of air containing volatile emissions from living plants has been elaborated. The qualitative composition of volatile organic compounds (VOC) produced by 22 species of plants which are characteristic for Northern hemisphere forests has been studied. The emission rate of isoprene and terpenes for some of them has been determined. Terpene concentrations in coniferous forests of different regions of the U.S.S.R. have been also determined. The list of compounds identified includes more than 70 substances of different classes. Total terpene concentrations in the coniferous forests air usually vary from 3.5 to 35 μg −3 . Strong influence of meteorological conditions on the emission rate and terpene concentrations in the air under the forest canopy has been noted.

Gas chromatographic-mass spectrometric determination of volatile organic compounds in an urban atmosphere

Polysorbimide and carbochrome, new sorbents with high temperature stability, have been used to concentrate trace amounts of atmospheric pollutants, and 136 C1-C13 organic compounds, including 126 hydrocarbons, 6 oxygen derivatives and 3 chlorides, were identified in air samples collected in the streets of Leningrad. One of the major features of the composition of the organic constituents of the urban air sampled is the presence of a number of CnH2n hydrocarbons (mainly olefins), and also CnH2n-2 and CnH2n-4 unsaturated hydrocarbons (including alpha-pinene and camphene). A comparison of the results with those of similar studies carried out on air samples from Zürich, Houston and Paris is of considerable interest in connection with the possible effect of geographical factors on the composition and lifetime of organic pollutants in the atmosphere.

Application of phase equilibria to gas chromatographic trace analysis

SummaryThe different ways of GLC determination of trace impurities using phase equilibria of the objects under investigation (head-space analysis and determination of impurities in a gas using the data of their content in the liquid saturated with this gas) are discussed and compared. The limits of application and the possible source of errors of each of these methods are discussed. Examples for application of the method of equilibrium concentration for GLC analysis of impurities in food, waste water, air and biological objects are given.

System of retention indices for a linear temperature programming regime

Abstract The possibilities and advantages of the recently proposed system of linear—logarithmic retention indices for chromatography with linear temperature programming are discussed. In contrast to previously known systems of retention indices, an additional parameter is introduced in which the experimental conditions are taken into account and which is determined from the retention times of reference compounds. The linear—logarithmic retention indices are characterized by high reproducibility under any conditions of linear temperature programming, irrespective of the choice of reference compounds, and can be directly compared with Kovats retention indices.

Methods and results of gas chromatographic-mass spectrometric determination of volatile organic substances in an urban atmosphere

Abstract The method and results of the quantitative gas chromatographic determination of volatile organic substances in an urban atmosphere are presented. The concentration of organic substances was determined by using a mixed adsorber consisting of graphitized thermal carbon black and activated charcoal modified by pyrocarbon. Average, maximum and minimum concentrations of constant organic components in the atmosphere of Leningrad as a typical large industrial city are reported.

Application of the headspace analysis to systems with unknown partition coefficients

SummaryPossibilities for the quantitative determination of volatile constituents in solutions by headspace analysis are investigated in cases where the partition coefficients (K) depend on the composition of the object under study. The timeconsuming work of revealing and taking into account the effect of the analytes and the other present constituents on the magnitude of K can be eliminated if simultaneously with determining the analyte content in the equilibrium gas one also measures the partition coefficients characteristic for the solution under study. These quantities can be obtained by repeated analysis of the equilibrium gas after partial removal of the volatile solution constituents. At small K (0.1 to 10) the required change of analyte concentration in the solution can be attained by single replacement of the equilibrium gas by pure gas, and at large K, by passing a known volume of pure gas through the solution under study under equilibrium conditions. The paper establishes the range of applicability of each version, provides the necessary equations and presents the results of an experimental check in the case of determining alcohol admixtures in water solutions.

Basic equations in continuous gas extraction and their application to headspace analysis

Abstract The evolution of ideas on the rules of continuous gas extraction based on dynamic headspace analysis is outlined. The application of a simpler exponential equation that describes well the course of gas extraction under the conditions of a sufficiently small volume of the vapour phase is recommended for practical purposes. The possibility of performing under non-equilibrium conditions not only stripping but also variants of the analysis that do not require full extraction of the sample components is considered. The expediency of the application of continuous gas extraction is demonstrated by the determination of volatile substances with low liquid—gas partition coefficients, where high sensitivity can be achieved by direct headspace analysis under static conditions.

Application of gas chromatographic headspace analysis to the characterization of chemical equilibria in solutions

Abstract The possibility is considered of using headspace analysis in studies of chemical equilibria in solutions of volatile organic compounds. The main theoretical relationships for the determination of the constants of X + Y ⇄ XY type equilibria by the gas chromatographic analysis of equilibrated vapour above a solution are derived. New methods are proposed and have been checked experimentally for the measurement of the ionization constants of volatile organic compounds, and of the stability constants of metal complexes with unsaturated and aromatic hydrocarbons.

New applications of gas chromatographic headspce analysis

Abstract The problems of the concentration dependence of liquid—gas distribution coefficients and the matrix effects in complex systems with non-volatile components have been considered. On the basis of the relationships established, methods of headspace analysis of aqueous alcohol solutions of non-volatile substances in medium and high concentration are proposed. The concept of the buffer properties of heterogeneous systems is introduced. Systems with high buffer coefficients can be used as standard mixtures for the calibration of gas chromatographic systems and components. Weakly buffered heterogeneous systems can easily be analysed by the method of discrete gas extraction and can serve for the preparation of standard mixtures with very low contents of volatile compounds. The application of headspace analysis to non-equilibrium systems is illustrated by an investigation of the volatile emissions from living plants. Data were obtained on the dynamics of emission of isoprene and terpenes by arboreous plants, and a number of compounds were detected the presence of which in plant emissions was previously unknown.

Determination of trace impurities in gases by their equilibrium accumulation in volatile liquids

Abstract A brief discussion is given of work devoted to the theoretical substantiation and experimental testing of a new method for the determination of trace amounts of organic compounds in gases by their concentration in a suitable volatile solvent and subsequent injection into a chromatograph after equilibrium has been reached. The method has substantial advantages over the known techniques of concentration of micro-amounts of impurities by adsorbents and non-volatile liquids, but its application is limited by the availability of a suitable solvent. Results are presented that illustrate the determination of simple aromatic hydrocarbons, carbonyl compounds and diethylamine in air at the level of 0.1–65 mg/m3.