Adsorbents and their application to column cleanup of pesticide residues

In any analysis for pesticide residues there is an interplay between the method of extraaion, the cleanup of the extract, and the technique used for the measurement of the residues. In addition the nature of the material being extraaed and of the pesticide or pesticides1 being sought must be considered. Thus extraas of vegetable materials, in general, pose far fewer problems than those of animal tissues. Similarly the cleanup requirements may be quite different for final estimation by colorimetry, bioassay, chromatography, and infrared spectrophotometry. It is therefore perhaps a mistake to try to isolate and review one step in a complicated interlocking procedure. Nevertheless, despite these limitations, this review will deal almost exclusively with adsorbents and their use in column cleanups. Particular emphasis will be given to techniques which lend themselves to the analysis of many pesticides and result in solutions suitable for analysis by modern instrumentation. No attempt has been made to make this a comprehensive literature survey since many of the older techniques were developed for use with non-specific colori- metric methods which are rarely used nowadays and will probably be even less used in the future. In addition many workers now use well documented procedures with little, if any, modifications apart from those required by variation in adsorbent properties.