Sample preparation volatile organic compound

Namiesnik et al. [33] have reviewed the analysis of soils and sediments for organic contaminants. They discuss methods of sample preparation and isolation-preconcentration prior to instrumental determination. Compound classes discussed include volatile organic compounds, polychlorobiphenyls, polyaromatic compounds, pesticides and polychlorodibenzo-p-dioxins and polychlorodibenzofurans. 

The most variable aspect of carbon tetrachloride analysis is the procedure used to separate carbon tetrachloride from the medium and prepare a sample suitable for GC analysis. As a volatile organic compound of relatively low water solubility, carbon tetrachloride is easily lost from biological and environmental samples, so appropriate care must be exercised in handling and storing such samples for chemical analysis. Brief summaries of the methods available for extraction and detection of carbon tetrachloride in biological and environmental samples are provided below. 

Helmig, D "Artifact-Free Preparation, Storage, and Analysis of Solid Adsorbent Sampling Cartridges Used in the Analysis of Volatile Organic Compounds in Air, J. Chromatogr. A, 732, 414-417 (1996). 

Hewitt, A.D., Comparison of sample preparation methods for the analysis of volatile organic compounds in soil samples solvent extraction vs. vapor partitioning, /. Environ. Sci. Technol., 32(1), 143-149, 1998. 

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. 

Helmig, D. (1996) Artefact-free preparation, storage and analysis of solid adsorbent sampling cartridges used in the analysis of volatile organic compounds in air. Journal of Chromatography A, 732, 414-17. 

ISO (2006c) 16000-11. Indoor Air-Determination of the Emission of Volatile Organic Compounds from Building Products and Furnishing-Sampling, Storage of Samples and Preparation of Test Specimens,... 

X-ray fluorescence,1516 surface acoustic waves (SAW) for determining volatile organic compounds (VOCs),17 18 and immunoassays19-21 are examples of direct analytical techniques (in which a sample preparation step is unnecessary) that are environmentally friendly. In addition, there are environmentally benign procedures from which reagents and solvents have been eliminated or their quantities minimized (calculated per analytical cycle) ... 

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. 

Examples of the application of headspace extraction are flavors in food products, volatile organic compounds in soils, and residual solvents in pharmaceutical products [33, 34]. The main advantages of headspace extraction are minimal sample preparation and the possibility for direct introduction of headspace gas into the gas chromatograph. 

Ueta, I., Mizuguchia, A., Fujimura, K., Kawakubo, S., Salto, Y. Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples. Anal. Chim. Acta 746, 77-83 (2012)... 

Uehori and co-workers (1987) developed a retention index in GC to screen and quantify volatile organic compounds in blood. A dynamic headspace analyzer and GC/FID with retention indices were employed for the detection of 1,1-dichloroethane at nanogram levels. Uehori and co-workers noted that this method is simple, reliable and requires little or no sample preparation. 

EN 13419-3 (2003) Building products - determination of the emission of volatile organic compounds, part 3 procedure for sampling, storage of samples and preparation of test specimens. Beuth, Berlin... 

Solid-phase microextraction (SPME) is a technique that was first reported by Louch et al. in 1991 (35). This is a sample preparation technique that has been applied to trace analysis methods such as the analysis of flavor components, residual solvents, pesticides, leaching packaging components, or any other volatile organic compounds. It is limited to gas chromatography methods because the sample must be desorbed by thermal means. A fused silica fiber that was previously coated with a liquid polymer film is exposed to an aqueous sample. After adsorption of the analyte onto the coated fiber is allowed to come to equilibrium, the fiber is withdrawn from the sample and placed directly into the heated injection port of a gas chromatograph. The heat causes desorption of the analyte and other components from the fiber and the mixture is quantitatively or qualitatively analyzed by GC. This preparation technique allows for selective and solventless GC injections. Selectivity and time to equilibration can be altered by changing the characteristics of the film coat. 

We now turn our attention to sample preparation techniques to quantitatively determine volatile organic compounds (VOCs) in environmental samples, and after this, we return to a discussion of the more recently developed sample prep techniques for SVOCs. Because we have been discussing LLE and LSE techniques, it is appropriate for us to ask at this point the following question. 

Determination of Priority Pollutant Volatile Organic Compounds (VOCs) in Wastewater Comparison of Sample Preparation Methods— pLLE versus Statis Headspace Sampling... 

Slack, G.C. Snow, N.H. Kou, D. (2003) extraction of volatile organic compounds from solids and liquids, in Sample Preparation Techniques in analytical chemistry, Mitra, S., 183-225. John Wiley Sons, Canada. 

Snow N, Slack G, and Kou D (2003) Extraction of volatile organic compounds from solids and hquids. In Mitra S (ed.) Sample Preparation Techniques in Analytical Chemistry. New Jersey Wiley. 

Figure 4.8 Set up for sampling volatile organic compounds from the coffee flow. Volatiles were introduced into the dilution lance by a flow created with a vacuum pump and were then diluted 7.5 fold using dried compressed air containing a standard for mass calibration [187]. Reprinted with permission from Sinchez-Lopez, J.A., Zimmermann, R., Yeretzian, C. (2014) Insight into the Time-resolved Extraction of Aroma Compounds during Espresso Coffee Preparation Online Monitoring by PTR-ToE-MS. Anal. Chem. 86 11696 11704. Copyright (2014) American Chemical Society...

---