A simple HPLC-DAD method for simultaneous detection of two organophosphates, profenofos and fenthion, and validation by soil microcosm experiment.

Abstract

Indiscriminate use of two broad spectrum pesticides, profenofos and fenthion, in agricultural system, often results in their accumulation in a non-target niche and leaching into water bodies. The present study, therefore, aims at developing a simple and rapid HPLC method that allows simultaneous extraction and detection of these two pesticides, especially in run-off water. Extraction of the two pesticides from spiked water samples using dichloromethane resulted in recovery ranging between 80 and 90%. An HPLC run of 20min under optimized chromatographic parameters (mobile phase: methanol (75%) and water (25%); flow rate of 0.8mlmin-1; diode array detector at wavelength 210nm) resulted in a significant difference in retention times of two pesticides (4.593min) which allows a window of opportunity to study any possible intermediates/transformants of the parent compounds while evaluating run-off waters from agricultural fields. The HPLC method developed allowed simultaneous detection of profenofos and fenthion with a single injection into the HPLC system with 0.0328mgl-1 (32.83ngml-1) being the limit of detection (LOD) and 0.0995mgl-1 (99.5ngml-1) as the limit of quantification (LOQ) for fenthion; for profenofos, LOD and LOQ were 0.104mgl-1 (104.50ngml-1) and 0.316mgl-1 (316.65ngml-1), respectively. The findings were further validated using the soil microcosm experiment that allowed simultaneous detection and quantification of profenofos and fenthion. The findings indicate towards the practical significance of the methodology developed as the soil microcosm experiment closely mimics the agricultural run-off water under natural environmental conditions.