PACKED-CAPILLARY SUPERCRITICAL FLUID CHROMATOGRAPHY OF PESTICIDES USING PHOSPHORUS-SELECTIVE DETECTION

Packed-capillary, supercritical fluid chromatography using carbon dioxide modified with methanol or 2-propanol as mobile phase, was coupled with a thermionic detector for phosphorus-selective detection. Optimum conditions for thermionic detection were established for a number of hydrogen flow rates by adjusting the air flow rate and bead position. Using the mentioned modifiers, a series of organophosphorus pesticides of varying polarity could be separated within 8 min. An optimum sensitivity of 55-128 fg P/s and linearity over four orders of magnitude were obtained. The detector showed good selectivity for phosphorus over carbon and nitrogen, viz., 9 . 10(4) g C/g P and 75 g N/g P, respectively. This was demonstrated by determining pesticides such as phoxim, dimethoate and azinphos-methyl in onion and tomato extracts.