Polychlorinated biphenyls analytical methods

With the recent Increase In activity at hazardous waste sites where cleanup and remedial action are underway, there has emerged a need for rapid analytical methods for assessing contamination in water, sediment, and soil. Of special Interest, because of widespread use and disposal. Is the group of materials known as PCB s (polychlorinated biphenyls). 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

B. Richter, J. EzzeU, and D. Felix, Single Laboratory Method Validation Report Extraction of Organo-phosphorus Agrochemicals, Chlorinated Herbicides and Polychlorinated Biphenyls Using Accelerated Solvent Extraction (ASE) with Analytical Validation by GC/NPD and GC/ECD, Document 101124, Dionex Sunnyvale, CA (1994). 

Two-dimensional GC can be used to separate complex mixtures of polyaromatic compounds, and MS used to subsequently identify the compounds. In this method, the original sample is injected into a gas chromatograph with one type of column. As the components exit the first GC, they are fed into a second GC, with a different column, for further separation and finally into a mass spectrometer. In this way, compounds that coeluted from the first column are separated on the second. Focant et al. [19] were able to separate polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) using this type of analytical procedure, including isotope dilution TOF-MS. These compounds are frequently found as contaminants in soils surrounding industrial settings thus, the ability to separate and identify them is extremely important [6,12,19],... 

One advance in the area of LLE is the use of solid supports that facilitate the partitioning of the analyte(s) of interest. LLE extraction methods involving nonpolar matrices often suffer from the formation of emulsions, and using the solid support is a possible solution. In one study, polychlorinated biphenyls, dioxins, and furans were extracted from the lipid fraction of human blood plasma [32], using diatomaceous earth as the solid support. Long glass columns (30 cm) were packed with several layers of Chem-Elut (a Varian product) and sodium chloride. The plasma samples were diluted with water and ethanol and passed over the columns. A mixture of isopropanol and hexane (2 3) was passed over the column and the LLE was performed. It can be concluded that the LLE with the solid support is easier to perform and can be applied to other lipid heavy matrices such as milk [32]. 

Alford Stevens et al. [49] carried out a multi-laboratory study of automated gas chromatography-mass spectrometric determinations of polychlorinated biphenyls in soil. The influence of various factors on the accuracy of analytical results were studied. Shaker extraction for 12.5h followed by Florisil chromatography were demonstrated to be the most reliable methods for extraction and clean-up. 

Based on the examination of analytical data from polychlorinated biphenyls (PCBs), OCPs and PAHs spiked into SPMDs, which have subsequently been subjected to the entire SPMD analytical procedure described herein, recoveries are generally >75% with good precision (i.e., C.Fs < 20%). Surprisingly, the C. Vis for the analysis of contaminants present in replicate SPMDs deployed contiguously at the same sites and treated identically during analysis are often equivalent to C.Fs of SPMD spikes. This observation suggests that the variability of analyte sampling rates of replicate SPMDs in the field is small and that the analytical methods used for field-deployed SPMDs are robust. 

For example, in eel, high concentrations of polychlorinated biphenyls can be present and can interfere in the cleanup procedure. Fly ash is difficult to extract. Drastic concentration and cleanup procedures such as saponification can convert some isomers. Oc-tachlorodibenzo-p-dioxin can easily be broken down during the cleanup procedure. For each matrix a specific isolation technique is necessary. The method has to be validated for all the isomers of the analytical program (24). 

Where analytical methods are available it is largely because of a crossfertilisation of effort from well-established areas of food contaminants work. For example, the steady development since the 1960s of methods of analysis for chlorinated pesticides led to the analysis of food for polychlorinated biphenyls (PCBs) since PCBs were readily detectable by general methods used to analyse food for organochlorine pesticides. The analysis of food for chlorinated dioxins and furans (PCDDs and PCDFs) at the very low levels at which they are found in food is a more recent development, and one that is an important precedent since it arose from interest in environmental contamination rather than because of cross-fertilisation of scientific methodology from an established area of food chemistry. Although dioxins were detectable some years ago at much less sensitivity in some pesticides, it was environmental interest that led to their study at very low levels in the food chain. 

Enzyme immunoassay kits are now available for qualitative field testing or for laboratory screening and semiquantitative analysis of pesticides, herbicides, polychlorinated biphenyls (PCBs), mononuclear and polynuclear aromatic hydrocarbons, pentachlorophenol, nitroorganics, and many other compounds in aqueous and soil samples. Certain analytes may be quantitatively determined as well, with a degree of accuracy comparable to gas chromatography or high performance liquid chromatography determination. The method is rapid and inexpensive. 

The toxicity, bioaccumulative potential, and ecological impact of organohalogenated substances such as polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated d iben zo -pa ra - diox i n s (PCDDs), or polybrominated diphenylethers (PBDEs) have been extensively reviewed.95 98 All are referred to as persistent organic pollutants (POPs), that is, chemical substances that remain in the environment, bioaccumulate through the food chain, and pose a risk to human health and the environment. The international community is calling for action to reduce and then eliminate the production or formation of these substances and to monitor their emission. In this case, the detectability obtainable by analytical methods should be very low, since the limits established for these residues are in the ng per liter range. 

HRGC/MS methods (40-102%) (Creaser and Al-Haddad 1989 Donnelly et al. 1986 Simon et al. 1989). Polychlorinated biphenyls, polychlorinated diphenyl ethers, polychlorinated naphthalenes, and polychlorinated alkydibenzofurans may be found at concentrations several orders of magnitude higher than the analytes of interest (EPA 1994a) and could thus interfere with the CDDs. Retention times must be verified using reference standards. 

An analytical method is used to determine polychlorinated biphenyls in transformer oil by solvent extraction and gas chromatography. The precision is quoted as 10% (2 standard deviations). However, this value needs to be qualified to be of use, i.e. does it refer to ... 

The first considerations in determining the most appropriate SPE methodology are the structure and polarity of the analytes of interest. Table 7.1 shows a selection of environmentally important compounds as examples for SPE methods development from aqueous solution. The polarity range of environmentally important analytes is broad and stretches from nonpolar compounds, such as polychlorinated biphenyls (PCBs), dioxin, and l,l,l-trichloro-2-2-bis(4-chlorophenyl)ethane (DDT), to moderately nonpolar compounds, such as polynuclear aromatic hydrocarbons (PAHs), to polar compounds such as the herbicides. The most polar compounds are those containing multiple polar functional groups or an ionic functional group, either anionic or cationic. The type of SPE cartridge and elution solvent that are used depends on the polarity of the compound. 

The extraction of Polychlorinated Biphenyls (PCBs) from water may effectively be accomplished with C-18 and a reversed-phase mechanism. The method is similar to the PAH method and consists of isolation of the analytes from a 1 -L sample, followed by elution with ethyl acetate followed by methylene chloride. The combination of solvents is needed for the hydrophobic nature of PCBs. The disk is cleaned with the elution solvents before addition of the sample. 

Analytical Methods for Determining Polychlorinated Biphenyls in Biological Samples... 

Analytical Methods for Determining Biomarkers for Polychlorinated Biphenyls... 

Greizerstein HB, Gigliotti P, Vena J et al. 1997. Standardization of a method for the routine analysis of polychlorinated biphenyl congeners and selected pesticides in human serum and milk. J Analytical Toxicol 21 125-133. 

Soil contamination also can be very difficult to detect. New analytical methods have made it possible to detect and analyze dioxins, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Analytical techniques have made it possible to detect the presence of these substances, determine whether remediation is needed, and evaluate the extent to which it has been carried out. Chemistry has provided or contributed to the remediation technologies that have been developed,... 

Abstract. The distribution of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the environment has not been systematically studied in Bulgaria in spite of their negative effect on the human health. The aim of this study is to develop a cost-effective method for determination of low concentrations of PCBs and OCPs in soils. After extraction with hexane/acetone and column cleaning with silica, the analyses was performed by gas chromatography with electron-capture detector. The limit of detection is between 0.1 and 1 ng g 1, the reproducibility at low environmental levels is about 15% RSD. The analytical recoveries for the individual compounds are between 65% and 100%. The method can be applied to study the sources of pollution, the migration and biogeochemistry of PCBs in the environment. 

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