Cleanup procedures, pesticide residue

Multi-residue Method S19 of the DFG Manual,including Cieanup Procedure Xll-6 (gel-chromatographic cleanup), has been used successfully in many laboratories because of its broad applicability for the gas-chromatographic determination of pesticide residues in foodstuffs. DFG method S19 is also included in the respective European Standards. Subsequently, a modification of the extraction and partition step has been implemented. The modified method requires less experimental effort and eliminates the use of dichloromethane, which is an undesirable solvent for toxicological and ecological reasons. As the results from validation studies demonstrate,... 

Yurawecz MP, Puma BJ. 1986. Gas chromatographic determination of electron capture sensitive volatile industrial chemical residues in foods, using AOAC pesticide multiresidue extraction and cleanup procedures. J Assoc Off Anal Chem 69 80-86. 

The sensitivity of the overall analytical procedure depends upon many factors obviously including the type of sample to be analyzed and the skill of the analytical chemist. If an immunoassay is used to measure the amount of pesticide in a water sample by adding the water sample directly to the immunoassay, very high sensitivity may not be obtained although the assay will require very little time to perform. Alternatively, if the water sample is extracted and the immunoassay is employed only after several highly efficient cleanup steps, phenomenal sensitivity may be obtained at the expense of a large investment in time. In some situations, immunochemical methods may decrease the limit of detectability of a pesticide residue (77), but more importantly they may, in some cases, decrease the time and cost needed to reach a level of detectability as has been demonstrated with parathion (31). 

Chlorinated hydrocarbon pesticide residues in human adipose tissue and liver tissue samples have been identified by mass spectrometry coupled with gas chromatography. A general, extensive extraction and cleanup procedure adapted from existing methods was used to isolate... 

OP), and carbamate pesticides are available as standard methods by the AO AC covering both nonfatty and fatty foods. These methods are based on solvent extraction and a variety of column chromatographic cleanup procedures with determination by GC using selective detectors. The International Dairy Federation has approved similar methods for OC and OP pesticide residues in milk and milk products. The AOAC have standard methods for specific pesticides or groups of pesticides that are approved for certain foodstuffs these methods involve colorimetric, spectrophotometric, or gas chromatographic determination. In the case of me-thylcarbamate pesticides, a liquid chromatographic method is approved. 

Tekel, J. and Hatrik, S., Pesticide residue analyses in plant material by chromatographic methods cleanup procedures and selective detectors, /. Chromatogr. A, 754, 397,1996. 

A variety of methods have been developed for sampling pesticides in air. Suitable procedures must deal with difficulties posed by the uncertainty regarding the physical state (aerosols, solid particles, vapors) of airborne residues, their relatively low concentrations (less than 1 mg/m, ca 80 ppb), fluctuations in pesticide concentrations and the levels of potential interferences with time, potential reactivity during the sampling process, and limited availability of sampling devices. These are in addition to the problems of cleanup, recovery, quantitation, and confirmation which are common to trace analytical processes once the sample has been collected and brought to the laboratory for determination. 

Triazines such as atrazine, propazine or simazine, are widely used herbicides. Currently, the determination of atrazine in water and soil samples is mainly done by GLC (1,2) or HPLC (3-5). However, these procedures require cumbersome cleanup steps which could be avoided by using immunoassays as an alternative approach to residue analysis. Such immunochemical determination based on competitive binding of herbicides or pesticides to an antibody (6,7), has been described recently for s-... 

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