Volatile organic compounds headspace

Headspace analysis has also been used to determine trichloroethylene in water samples. High accuracy and excellent precision were reported when GC/ECD was used to analyze headspace gases over water (Dietz and Singley 1979). Direct injection of water into a portable GC suitable for field use employed an ultraviolet detector (Motwani et al. 1986). While detection was comparable to the more common methods (low ppb), recovery was very low. Solid waste leachates from sanitary landfills have been analyzed for trichloroethylene and other volatile organic compounds (Schultz and Kjeldsen 1986). Detection limits for the procedure, which involves extraction with pentane followed by GC/MS analysis, are in the low-ppb and low-ppm ranges for concentrated and unconcentrated samples, respectively. Accuracy and precision data were not reported. 

Pavlostathis SG, Mathavan GN. 1992. Application of headspace analysis for the determination of volatile organic compounds in contaminated soils. Environ Technol 13 23-33. 

Ramsey JD, Flanagan RJ. 1982. Detection and identification of volatile organic compounds in blood by headspace gas chromatography as an aide to the diagnosis of solvent abuse. J Chromatogr 240 423-444. 

A. Lattuati Derieux, S. Thao, J. Langlois, M. Regert, First results on headspace solid phase microextraction gas chromatography/mass spectrometry of volatile organic compounds emitted by wax objects in museums, Journal of Chromatography A, 1187, 239 249 (2008). 

Bakierowska, A.-M., Trzeszqzynski, J. (2003) Graphical method for the determination of water/gas partition coefficients of volatile organic compounds by a headspace gas chromatography technique. Fluid Phase Equil. 213, 139-146. 

Peng, J., Wan, A. (1997) Measurement of Henry s law constants of high volatility organic compounds using a headspace autosampler. Environ. Sci. Technol. 31, 2998-3003. 

Bianchi AP, Vamoy MS, Phillips J. 1991. Analysis of volatile organic compounds in estruarine sediments using dynamic headspace and gas chromatography mass spectrometry. J Chromatogr 542 413-450. 

This is an alternative technique to headspace analysis for the identification and determination of volatile organic compounds in water. The sample is purged with an inert gas for a fixed period of time. Volatile compounds are sparged from the sample and collected on a solid sorbent trap—usually activated carbon. The trap is then rapidly heated and the compounds collected and transferred as a plug under a reversed flow of inert gas to an external gas chromatograph. Chromatographic techniques are then used to quantify and identify sample components. 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

Table 15.4 Proton affinities of the constituents of clean air and of various volatile organic compounds. All volatile organic compounds with a higher proton affinity than H2O (166.5 kcal/mol) will be protonated with a very high efficiency when colliding with H3O+. This is the case for most of the volatile organic compounds in the headspace of coffee, with the exception of the natural constituents of clean air. In contrast, if NH4 is used as a chemical ionisation agent, only compounds with a proton affinity exceeding 204.0/kcal mol are ionised below dotted line). (Adapted from [190]) ...

F. Vilaplana, M. Martinez-Sanz, A. Ribes-Greus, and S. Karlsson, Emission pattern of semi-volatile organic compounds from recycled styrenic polymers using headspace solid-phase microextraction gas chromatography - mass spectrometry, J. Chromatogr. A, In Press, Accepted Manuscript -, 2010. 

Volatile organic compounds Comparison of solvent extraction, headspace analysis and vapour partitioning, methanol extraction [88]... 

Headspace analysis is the method of choice for determining volatile organic compounds in soil [178-183]. A limitation of this method is the incomplete desorption of the contaminants in soil-water mixtures, but this problem can be overcome through the addition of methanol to the sample [181]. Good recoveries of volatile organic compounds in soils were obtained via thermal vaporisation of the sample followed by Tenax GC trapping and gas chromatography-mass spectrometry. 

Stuart et al. [ 184] studied the analysis of volatile organic compounds in soil using an automated static headspace method. Recoveries increased in the or-... 

Various other workers have reported on the determination of volatile organic compounds in soils [186,187] and landfill soils [188]. Soil fumigants such as methyl bromide have also been determined by this technique [189]. Trifluoroacetic acid is a breakdown product of hydrofluorocarbons and hydrochlorofluorocarbon refrigerant products in the atmosphere and, as such, due to the known toxicity of trifluoroacetic acid, it is important to be able to determine it in the atmosphere, water and in soil from an environmental point of view [190]. In this method the trifluoroacetic acid is extracted from the soil sample by sulfuric acid and methanol, which is then followed by the derivatisation of it to the methyl ester. The highly volatile methyl ester is then analysed with a recovery of 87% using headspace gas chromatography. Levels of trifluoroacetic acid in soil down to 0.2 ng/g can be determined by the procedure. 

Headspace analysis has been employed in the extraction of dithiocarbamate insecticide in vegetables [227]. Other techniques occasionally used are vacuum distillation followed by gas chromatography-mass spectrometry in the determination of volatile organic compounds in leaves, steam distillation in the determination of organochlorine insecticides in fruit and vegetables [229], and water distillation followed by high-performance liquid chromatography in the determination of 2-aminobutane in potatoes [102,230]. 

Ultrasonic extraction, methanol extraction [147] and supercritical fluid extraction have all been applied to the extraction of or the determination of volatile organic compounds [121,122] in soils. However, methods based on headspace analysis or on mass spectrometry are now the methods of choice. 

Kawata et al. [ 128] have described the effects of headspace conditions on recoveries of volatile organic compounds from sediments and soils. Hewitt [129] compared three vapour partitioning headspace and three solvent extraction methods for the preparation of soil samples for volatile organic carbon determination in soils. Methanol extraction was the most efficient method of spiked volatile organic carbon recovery, which depended on the soil organic carbon content, the octanol-water partitioning coefficients of analytes and the extraction time. 

Papaefstathion and Luque de Castro [ 130] used pervaporation as an alternative to headspace analysis for the analysis of down to 1 ng/g of volatile organic compounds in soils. 

James and Stack [131] found that solid-phase microextraction is an effective technique for determining volatile organic compounds in landfill sites. The headspace above the sample was sampled. 

Colombo, A., De Bortoli, M., Knoppel, H., Schauenburg, H. and Vissers, H. (1990) Determination of volatile organic compounds emitted from household products in small test chambers and comparison with headspace analysis, in Walkingshaw, D.S. (ed) Proceedings of the 5th International Conference on Indoor Air and Climate, Toronto, Canada, Vol. 3 (ed. D.S. Walkinshaw), Vol. 3, pp. 599-604. 

Fig.8 FT-IR gas analysis system utilizing a 1/2 turn coiled HWG and a headspace sample vial. VOC volatile organic compound [46]...

Volatilization Loss of volatile organic compounds Proper sampling techniques, headspace-free sample containers, cold storage... 

Schroers, H.-J. and Jermann, E., Determination of physiological levels of volatile organic compounds in blood using static headspace capillary gas chromatography with serial triple detection, Analyst, 123, 715-720, 1998. 

The stir bar technique has been applied to headspace sorptive extraction (HSSE) [142-144], However, headspace techniques are discussed elsewhere, as they are more applicable to volatile organic compounds than to the semivolatile organic compounds that comprise the focus of this chapter. 

Static headspace extraction is also known as equilibrium headspace extraction or simply as headspace. It is one of the most common techniques for the quantitative and qualitative analysis of volatile organic compounds from a variety of matrices. This technique has been available for over 30 years [9], so the instrumentation is both mature and reliable. With the current availability of computer-controlled instrumentation, automated analysis with accurate control of all instrument parameters has become routine. The method of extraction is straightforward A sample, either solid or liquid, is placed in a headspace autosampler (HSAS) vial, typically 10 or 20 mL, and the volatile analytes diffuse into the headspace of the vial as shown in Figure 4.1. Once the concentration of the analyte in the headspace of the vial reaches equilibrium with the concentration in the sample matrix, a portion of the headspace is swept into a gas chromatograph for analysis. This can be done by either manual injection as shown in Figure 4.1 or by use of an autosampler. 

Headspace-GC-MS analysis is useful for the determination of volatile compounds in samples that are difficult to analyze by conventional chromatographic means, e.g., when the matrix is too complex or contains substances that seriously interfere with the analysis or even damage the column. Peak area for equilibrium headspace gas chromatography depends on, e.g., sample volume and the partition coefficient of the compound of interest between the gas phase and matrix. The need to include the partition coefficient and thus the sample matrix into the calibration procedure causes serious problems with certain sample types, for which no calibration sample can be prepared. These problems can, however, be handled with multiple headspace extraction (MHE) [118]. Headspace-GC-MS has been used for studying the volatile organic compounds in polymers [119]. The degradation products of starch/polyethylene blends [120] and PHB [121] have also been identified. 

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