Improving Analysis of Pesticides

Determination of pesticide contamination of fruit and vegetables usually follows several steps, including, extraction of analytes from the sample, concentrating the extract, post extraction clean-up, solvent exchange, and finally, determination of the analytes present. During sample preparation, evaporation becomes a critical step when the pesticides are semi-volatile compounds, because some of the compound may be lost during the concentration and evaporation stages. Analyte loss is detrimental to accurate analysis, and the official directives(1) must be satisfied with regard to minimum analyte recovery. Typically a minimum recovery of 70% must be achieved. In order to evaluate new instruments and improve productivity, which is also the remit of ARPAT, this study was done to determine how a new generation centrifugal evaporator may simplify the sample preparation process and improve analyte recovery. The study falls in two halves, first, an evaluation of the a new evaporator to determine the optimal concentration process; then, the study was addressed towards real matrices spiked with pesticides to validate the new methods. The new processes and methods were then compared to the original method validated in ARPAT laboratories..