A method developed for the extraction, detection and Quantification of organophosphorus pesticide in aqueous media

Abstract

Extraction of filtered river and canal water, fortified with five organophosphorus pesticides (OPs), was conducted using solid-phase extraction and eluted with a variety of solvent combinations. The best recoveries (70-110%) were obtained using 1:1 acetonitrile/dichloromethane. Liquid chromatography-mass spectrometric conditions were chosen that provided the optimum analyte resolution on a C₁₈  reverse-phase LC column, along with optimum selectivity and sensitivity for an ion-trap MS/MS detector. A mobile phase gradient consisting of water and methanol with the addition of 0.1% formic acid (to aid protonation) provided the optimum resolution and ionization of the OPs using electrospray ionization in the positive mode, respectively. The use of acetic acid, however, resulted in an interfering contaminant ion in all samples. The major OP ions and subsequent daughter ions used for both analyte confirmation and quantitative analysis were presented. Reproducibility of spiked water samples was <15% RSD for all compounds, with instrumental detections limits ranging over 0.20-~10  g/L, allowing this method to be applied for OP analysis in water samples collected in the vicinity of agricultural areas.

 Keywords: SPE, Daughter Ions, Mobile Phase, Water Samples