IMPURITIES RELEASED FROM EXTRACTIVE PHASES USED IN THE ANALYSIS OF PESTICIDES

Elution fractions relative to solid phase extraction (SPE) procedures using C-18 bonded silica and Carbopack B columns plus C-18 membranes h ave been analyzed by gas chromatography-mass spectrometry (GC-MS) for the characterization of interfering compounds from the phases. Alkanes , alkenes, phthalates and some silyl compounds (silanols, siloxanes) h ave been tentatively identified. Experiments on commercial C-18 phases prepacked in plastic tubes show that the increased interference compa red to the phases alone comes from the polymer container. N-butylbenze nsulfonamide (NBBSA) was identified as causing interference when the e xtraction device used for SPE involved plastic components. Increasing amounts of silanol interferences released from the C-18 phases were ob served after passage of the water sample, depending on the acidic pH, as evidence of the hydrolysis of the bonded silica.