DEVELOPMENT AND OPTIMIZATION OF A SOLID-PHASE EXTRACTION SCHEME FOR DETERMINATION OF THE PESTICIDES METRIBUZIN, ATRAZINE, METOLACHLOR AND ESFENVALERATE IN AGRICULTURAL RUNOFF WATER

Concomitant determination of the pesticides metribuzin, atrazine, meto lachlor and esfenvalerate in agricultural runoff water was developed u tilizing solid-phase extraction (SPE). A 2(5) factorial experimental d esign compared relative importance for extraction efficiency of the fi ve variables sample pH, elution solvent strength, ionic strength of th e sample, addition of organic modifier to the sample, and elution by g ravity or vacuum. The protocol was further optimized with respect to s orbent mass, sample volume, elution volume and concentration. The appr oach offers optimal recoveries, low detection limits, rapid extraction , and final determination by either gas or high-performance liquid chr omatography.