Polychlorinated biphenyls quantification

Smeds, A., Saukko, P., 2001. Identification and quantification of polychlorinated biphenyls and some endocrine disrupting pesticides in human adipose tissue from Finland. Chemosphere 44, 1463-1471. 

GC-MS can be used to analyze organochlorine pesticides, for example, a-, [3-, y-HCH, HCB, and polychlorinated biphenyls (PCB). The components are quantified by using an internal standard. Furthermore, a calibration is performed with a standard mixture containing known concentrations of the components to be measured and one or more components not contained in the sample (internal standards). The calibration is followed by injection of the sample containing known amounts of internal standards. Quantification is relative to the internal standard. In this way, the sample extract volume will not be included in the calculations, and it is not necessary to accurately determine the final sample volume after evaporation of the injection volume. The GC-MS instrument should be calibrated every day. The sensitivity of the mass spectrometer can, for instance, be controlled daily by determining the signal-to-noise ratio for a given amount of a chosen component (PCB-101 could be one such component). For further details of the method, the reader is referred to different manuals and papers on the subject.417... 

Gotz R, Enge P, Friesel P (1994a) Quantification of polychlorinated biphenyls (PCB) and hexachlorobenzene (FICB) in the picogram/liter range in water of the river Elbe. Fresenius J Anal Chem 348, 694-695. 

Other organic compounds Other dangerous substances include hydrocarbons (fats and oils), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins. Chromatographic methods (gas or liquid chromatography) are extensively used for separation and quantification of these groups. 

Finally, even if most of the pesticides worldwide are used in fruit and vegetable crops, data on pesticide residues in animal products are also essential, taking into account that livestock can be easily exposed to pesticides directly or through residues in their feed. For instance, the 2009 European Union Report revealed the presence of 34 different pesticides in animal products [115]. Garcfa de Llasera et al. [128] revealed the presence of chlofenvinphos and chlorpyrifos in liver samples, whereas a-endosnlfan, endosulfan sulfate, and dichloran have been reported in pork and lamb samples (<10 pg/kg) [129]. Bolafios et al. [130] studied the occurrence of organochlorine pesticides and polychlorinated biphenyls in chicken eggs. Benzene hexachloride and 28 polychlorinated biphenyl were detected in only one of the 30 samples at concentrations of 15 and 10 ng/g, respectively. However, five samples also contained traces of OC and PCB residues, even if at concentration levels below the limit of quantification. Einally, a-endosulfan and P-endosulfan were found in commercial milk-based infant formulas at concentration levels from 1.18 to 5.03 pg/kg [35]. The same study also showed the presence of fenitrothion, chlorpyrifos ethyl, and bifenthrin at maximum concentrations of 0.23,1.30, and 0.68 pg/kg, respectively. 

Bolanos, P. R, Frenich, A. G., and Vidal, J. L. M. 2007. Application of gas chromatography-triple quadrupole mass spectrometry in the quantification-confirmation of pesticides and polychlorinated biphenyls in eggs at trace levels. J. Chromatogr. A 1167 9-17. 

The described isotope dilution method for the quantification of polychlorinated dioxins, furans and dioxin-hke polychlorinated biphenyls (dl-PCBs) follows the EPA 1613 Rev.B method (US EPA, 1994,1998a/b). The MID scheme on the accurate target masses typically uses isotope ratio qualifiers besides the specific retention time for all native dioxin/furan congeners, as well as for their specific labelled internal standards, one quantification mass and one ratio mass. The analytical setup for the high resolution GC-MS is given with the MID descriptor, as... 

The detection and quantification of polychlorinated dibenzo-p-dioxins, and in particular the 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (2,3,7,8-TCDD), is a major application for double-focusing magnetic-sector mass spectrometers. Despite extensive clean-up procedures, samples still contain compounds such as polychlorinated biphenyls and benzyl phenyl ethers, which have the same nominal masses as the compounds of interest. The sample is spiked with a known amount of the isotope labelled form of 2,3,7,8-TCDD, introduced via gas chromatography and recorded by high-resolution mass spectrometry. The measurement is quantified by comparison of the native dioxin response to that from the C-labelled form, and verified by confirmation of the ratio of the major isotopes of both the native and the C-labelled dioxins. At 10 000 resolving power (10% valley definition) the detection level for 2,3,7,8-TCDD is about 1 femtogram, or 3 attomole (Figure 6). 

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