EVALUATION OF A SOLID-PHASE EXTRACTION SYSTEM FOR DETERMINING PESTICIDE-RESIDUES IN MILK

A simple and rapid procedure based on reversed solid-phase extraction with octadecylsilica was developed for determining chlorinated pestici de residues in milk. The need for an agent that breaks the fat globule s was first investigated and the method variables were optimized on wh ole homogenized milk (3.6% fat content). Recovery experiments performe d for 26 organochlorine pesticides at levels of 3-40 mug/l gave > 80% recoveries for all the compounds. The method was validated and evaluat ed by comparison with two widely used liquid-liquid extraction methods . The performance was checked by analysis of a certified standard with natural low endogenous levels (CMR 187) and different kinds of milk ( skimmed, 2%, powdered, evaporated and condensed) spiked with the 26 pe sticides. The procedure was used to analyse 45 commercial milks in whi ch the presence of organochlorine residues had been detected. The prop osed method offers advantages such as low cost and simplicity and the fact that the extracts obtained do not require a purification step.