Preconcentration and determination of high leachable pesticides residues in water using solid-phase extraction coupled with high-performance liquid chromatography

A multi-residue procedure was developed for analysis of four common pesticides in water using solid-phase extraction and high-performance liquid chromatography in combination with UV detection at 230 nm. The investigated pesticides (atrazine, dicloran, metazachlor and simazine) are highly leachable and easily migrate within the soil. Multi-walled carbon nanotubes (MWCNTs) adsorbent outperformed C18 bonded silica and graphitized carbon black for preconcentration of the pesticides from solution. The optimum experimental conditions for pesticides extraction were carefully studied and optimised. At the optimum preconcentration conditions (sample volume: 700 mL; adsorbent mass: 300 mg; solution pH: 5.0; flow rate: 3.0 mL min-1; and elution medium: methanol), a quantitiative recovery for pesticides was reported and a high preconcentration factor (1400) was attained. The detection limits of the proposed method were found in the range: 5-15 ng L-1. The dynamic range for simazine and atrazine determination was extended from 15 to 1000 ng L-1, while for metazachlor and dicloran the range was within 60-1000 ng L-1. Five replicate determinations of 70 ng of pesticides mixture present in 700 mL solution gave good results with RSD values within the range 2.5 to 4.6%. The present method gave recoveries from 92.7 to 95.3% for determination of 100 ngL-1 of pesticides in tap water and recoveries from 85.3 to 87.0 in well water with satisfactory RSD values (≤6%).