Determination of selected organophosphorus pesticides using GC-MS in aqueous samples
A reproducible analytical method utilising GC-MS is presented for the analysis of thirteen organophosphorus insecticides (OPs) often found in environmental aqueous samples. Extraction of filtered river and canal water (100 mL), fortified with the 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. The major OP ions and subsequent product ions used for both analyte confirmation and quantitative analysis are presented. Although chromatographic peak shape was poor on a low polarity column (5% phenyl methyl) for the more water soluble compounds of malathion and dimethoate, reproducibility of spiked water samples was -1 <15% RSD for all compounds, with instrumental detection limits ranging over 0.046 - 0.176 ngL . This makes the described method to be applied for OPs analysis in water samples.
Keywords: Insecticides, Solid Phase Extraction, Product Ion, Gas Chromatography, Mass Spectrometry