Pesticide levels, analytical methodology

A. G. Kelly, I. Cruz, D. E. Wells, Polychlorobiphenyls and persistent organochlorine pesticides in sea water at the pg T level. Sampling apparatus and analytical methodology. Anal. Chim. Acta., 276 (1993), 3-13. 

A large number of analytical methodologies aiming the detection of pesticide residues in VOO at very low concentration levels are being published nowadays. Among them, GC remains the most extensively used technique in routine laboratories for the analysis of these analytes in VOO it is usually employed in combination with ECD, NPD, and EPD. However, the relatively low sensitivity needed for some pesticides and the difficulties in confirmation of results due to the complexity of the matrix under study force to use GC-MS. With the use of GC-MS/MS techniques, simultaneous determination and confirmation of pesticide residues has been obtained in one analytical run this improves the analytical accuracy and shortens the analytical time [112,113],... 

In terms of specificity in isolation, one will also isolate food constituents that are not aroma compounds (e.g. pesticides, herbicides, PCBs, plasticisers, and some antioxidants). Since these compounds are typically present in foods at very low levels, they generally present few complications. The primary volatile that complicates the application of this methodology is water. In all cases, one obtains an aroma isolate that consists of volatiles in an aqueous solution . Thus, unless the amount of water is small and the subsequent analytical step is tolerant of some water, volatility-based techniques must include some water-removal process. This may be freeze-concentration, the addition of anhydrous salts, or solvent extraction. Distillation is often used to isolate aroma compounds from fat-containing foods. Since fat is not volatile (under isolation conditions), its presence does not prohibit the use of this methodology. 

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. 

There is an increasing awareness of the potential environmental and health hazards of trace levels of pesticides, their trace impurities as well as metabolites and/or degradation products. Hence, there is a need to develop and refine requisite analytical and toxicological methodologies for the detection and estimation of these agents as well as their biological and toxicological activity. 

---