Pressurized capillary electrochromatography with indirect amperometric detection for analysis of organophosphorus pesticide residues

Abstract

A new analytical method, pressurized capillary electrochromatography with indirect amperometric detection, has been developed for the determination of some non-electroactive organophosphorus pesticides (OPPs). When 0.1 mmol L⁻¹ of 3,4-dihydroxybenzylamine (DHBA) was added to the mobile phase containing 50% v/v of ACN and 50% v/v of MES buffer (10 mmol L⁻¹, pH 5.5), and +0.9 V (vs. Ag/AgCl) of working potential were used, maximal signal levels of analytes could be achieved. A separation voltage of +10 kV, a column pressure of 7.0 MPa and a pump flow rate of 0.05 mL min⁻¹ were selected as the other optimal conditions for separation of six OPPs, namely, dimethoate, methyl parathion, ethyl parathion, chlorpyrifos, chlorpyrifos-methyl, trichlorfon. The OPPs could be separated within 15 min and determined with the detection limits ranging from 0.008 to 0.2 mg/kg. Combining with a solid phase extraction procedure, mean recoveries between 78.9 and 87.2% for vegetable samples and from 81.4 to 98.6% for fruit samples were obtained.