Environmental analysis polar pesticides

E. A. Hoogendoom and P. van Zoonen, Coupled-column reversed phase liquid chromatography as a versatile technique for the determination of polar pesticides in Environmental Analysis - Techniques, Applications and quality assurance, Barcelo D (Ed.), Vol. 13, Elsevier, Amsterdam, pp. 181-196 (1993). 

One of the known disadvantages of the use of GC is the need for previous derivatization of some of the most polar pesticides before analysis can be carried out [40]. These derivatization steps might produce low-efficiency results in complex wastewater matrices, which make the analysis rather difficult and cumbersome. However, the reproducibility in retention times when using GC techniques is so precise, that specific identifications of pesticides can be made even in complex environmental samples. 

Supercritical carbon dioxide effectively extracts the nonpolar compounds from aU soil types. The extraction of more polar compounds, such as chlo-rophenols and some pesticides requires that a polar compound, such as a short-chain alcohol is added to the carbon dioxide. Supercritical carbon dioxide extraction is used by environmental analysis laboratories as a more efficient, occupationally more acceptable method for analyzing contaminated soils (Laitinen et al., 1994). 

Reversed-phase chromatography is the most popular mode for the separation of low molecular weight (<3000), neutral species that are soluble in water or other polar solvents. It is widely used in the pharmaceutical industry for separation of species such as steroids, vitamins, and /3-blockers. It is also used in other areas for example, in clinical laboratories for analysis of catecholamines, in the chemical industry for analysis of polymer additives, in the environmental arena for analysis of pesticides and herbicides, and in the food and beverage industry for analysis of carbohydrates, sweeteners, and food additives. 

The Food and Drug Administration [FDA] Pesticide Analytical Methods Manual QJ and the Environmental Protection Agency [EPA] Manual for Environmental Analysis (2) describe procedures that have been used for many years. Two of the commonly applied techniques are liquid-liquid partitioning and column adsorption chromatography. These approaches are used to isolate lipohilic and moderately polar residues for primary identification and quantitation with GLC. An evaluation of the number of pesticide residues that were satisfactorily analyzed by this approach was published by McMahon and Burke (3). When one looks at the data it can be seen that the highly polar and water soluble residues do not fit into the analytical scheme very well. In an attempt to rectify this problem, FDA is modifying the multiresidue method... 

As in other areas of analysis, HPLC is a useful complementary technique to GLC in analyzing pollutants in the environment. An advantage of HPLC in environmental analysis is that molecules of varying polarity (e.g. pesticide + metabolite mixtures) can be analyzed in one chromatographic run. Since aqueous mobile phases can be used in reversed-phase HPLC (including ion-pair partition modes) sample preparation is often less extensive than in GLC. The number of clean-up steps can also be reduced by the use of a precolumn to protect the analytical column or by a preliminary size separation of a crude extract on an exclusion column. 

Martin-Esteban, A., Fem idez, P., Femandez-Alba, A., and Camara, C., Analysis of polar pesticides in environmental waters a review, Quim. Anal, 17, 51-66, 1998. 

The use of HPLC is important for pesticide analysis because it is suitable for determining thermally labile and polar pesticides which require prior derivatization if these are to be determined by GC. HPLC methods for the determination of pesticides in environmental samples could employ reversed-phase chromatography with Cig or Cg columns and an aqueous mobile phase, followed by UV, fluorescence, or mass spectrometric detection.In addition to GC-MS or GC-ECD methods... 

Slohodnik, J., Brinkman, UA.Th. LC/ MS interfacing systems in environmental analysis Applications to polar pesticides, in Analytical Chemistry, Vol. 21, Sample Handling, Trace Analysis of Pollutants - Techniques, Applications, Quality Assurance, ed. Barcelo, D., Elsevier, Amsterdam 2000, p. 935. 

Multiresidue methods are the most powerful procedures for the analysis of pesticides in environmental, food, and/or feed samples. The maximum residue limits of the pesticides prescribed by health authorities include not only the residues of the parent compounds but their toxic metabolites as well. There is also a trend toward inclusion of residues of highly polar and conjugated metabolites (126). The ever-increasing demands on the quality of food, feed, and environmental samples, and the lowering of the maximum residue limits, require the development of new and more sensitive methods. To distinguish the pesticide signals from the interfering coextractives of samples demands more selective detection. TLC methods alone are not sufficient and should be combined with GLC, HPLC, mass spectrometry, etc. 

Martin-Esteban A, Fernandez P, Femandez-Alba A, Camara C (1998) Analysis of polar pesticides in environmental water. Quim Analytica 17 51-66... 

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