Environmental analysis PCBs

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

A typical example of MDGC in environmental analysis is the determination of PCBs. These are ubiquitous contaminants of the environment in which they occur as complex mixtures of many of the 209 theoretically possible congeners. The compositions of environmental mixtures vary according to sample type. 

The quantitative environmental analysis of surfactants, such as alcohol ethoxylates, alkylphenol ethoxylates (APEOs) and linear alkylbenzene sulfonates (LASs), is complicated by the presence of a multitude of isomers and oligomers in the source mixtures (see Chapter 2). This issue bears many similarities to the quantitation problems that have occurred with halogenated aromatic compound mixtures, e.g. polychlorinated biphenyls (PCBs) [1]. 

WP Cochrane, D Chaput, J Singh. Analysis of pesticides and PCB residues in water, soil and plant material. In Stevenson D, Wilson ID, eds. Sample Preparation for Biomedical and Environmental Analysis. New York Plenum Press, 1994, pp 191-201. 

Supercritical fluid extraction conditions were investigated in terms of mobile phase modifier, pressure, temperature and flow rate to improve extraction efficiency (104). High extraction efficiencies, up to 100%, in short times were reported. Relationships between extraction efficiency in supercritical fluid extraction and chromatographic retention in SFC were proposed. The effects of pressure and temperature as well as the advantages of static versus dynamic extraction were explored for PCB extraction in environmental analysis (105). High resolution GC was coupled with SFE in these experiments. 

GC X GC offers unparalleled resolving power. It can separate components of very complex mixtures, for example all 209 PCB congeners, which is impossible using ID GC. It can also potentially simplify sample preparation before chromatographic analysis by eliminating the need for extensive sample clean-up when the analytes of interest can be chromatographically separated from the matrix components. Consequently, GC X GC has tremendous potential in environmental analysis, especially in combination with TOF mass spectrometry. 

The OCs and PCBs were first determined in wastewaters using EPA Method 608 (2). This method originally required packed columns, and because of this, it necessitated extensive sample preparation and cleanup techniques which included liquid-liquid extraction and low-pressure column liquid chromatography. Capillary GC-ECD when combined with more contemporary methods of sample preparation provides for rapid and cost-effective trace environmental analysis. Over the past 10 years, there has been dramatic improvements in sample preparation techniques as this relates to semivolatile and nonvolatile trace analyses. 

Liquid-liquid extraction is used extensively in environmental analysis to extract and concentrate organic compounds from aqueous samples. Examples include the extraction of pesticides, PCBs,... 

In the field of environmental analysis, thermal extraction is proposed by an EPA method for the quantitative analysis of semi-volatile compounds from solid sample materials. The US EPA method 8275 is a thermal extraction capillary GC-MS procedure for the rapid and quantitative determination of targeted PCBs and PAHs (polynuclear aromatic hydrocarbons) in soils, sludges and solid wastes. This method requires extraction temperatures of 340 C for 3 min for the quantitative desorption of the PCBs (EPA, 1996). 

Use Environmental analysis, for example, volatile halogenated hydrocarbons, PCBs. Selective detection of amines, for example, in packaging or foodstuffs. Determination of sulfur-containing components. 

Due to the widespread use of PCBs as dielectric and heat-transferring fluids in power transformers, hydraulic fluids, intense use as plasticizers and flame retardants and due to their stable molecular structure, PCBs with its 209 possible congeners, are still today subject to be monitored in environmental analysis (US EPA,... 

Kannan, K., Tanabe, S., and Borrell, A. et al. (1993). Isomer specific analysis and toxic evaluation of PCBs in striped dolphins affected by an epizootic in the western Mediterranean sea. Archives Environmental Contamination and Toxicology 25, 227-233. 

In actual practice, environmental samples which are contaminated with PCB are also highly likely to be contaminated with chlorinated insecticides. Many reports have appeared discussing co-interference effects of chlorinated insecticides in the determination of PCB and vice versa, and much of the more recent published work takes account of this fact by dealing with the analysis of both types of compounds. This work is discussed below. 

Because component-based analysis of PCBs has limited the usefulness of the historical database for current environmental research and in formulation of regulatory criteria, procedures were... 

Rowan, DJ. and J.B. Rasmussen. 1992. Why don t Great Lakes fish reflect environmental concentrations of organic contaminants An analysis of between-lake variability in the ecological partitioning of PCBs and DDT. Jour. Great Lakes Res. 18 724-741. 

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