HPLC Silica Column Fractionation of Pesticides and PCB from Butterfat

Abstract

Separation of trace levels of toxic pesticides and other chemical contaminants (e.g., PCB) from edible fats and oils in preparation for quantitation by gas chromatography (i.e., GC-EC, GC-MS, etc.) continues to be an important analytical concern. Commercial HPLC silica columns were evaluated for practical application to the fractionation of selected compounds of different polarity from butterfat. Samples were injected in hexane solution and fractionated using isocratic hexanemethylene chloride mobile phases. Fat was readily purged from the columns with methylene chloride. A 254-nm UV detector was used to monitor elution patterns of concentrated standard solutions and of lipid material. Analyte fractions subsequently collected from samples fortified at sub-ppm levels were analyzed by GC-EC after concentration into hexane. A semi-preparative HPLC silica column (25 cm × 9.4 mm i.d., 6 um spheres) provided complete separation of organochlorine compounds and partial separation of organophosphorous pesticides tested from at least 500 mg of fat. This column was shown to be superior to the “official” (AOAC) Florisil column with regard to resolution, speed of elution, solvent volume required, and loading capacity. The column, which operated at moderate pressures of >1000 psi, proved to be resilient and reproducible to repeated sample injections, frac tionations and purgings made from either end.