Multi-Component Analysis of Pesticides in Water Samples by Hplc. Rapid Extraction and Neutral/Acid Fractionation by a Carbopack Cartridge

Abstract

A liquid-solid extraction procedure for isolation of 70 pesticides from ground and tap waters for high-performance liquid chromatography (HPLC) is presented. This simple and rapid procedure involved passing a 2-L sample through a 250-mg graphitized carbon black (Carbopack B) cartridge at a flow-rate of 120-140 mL/min. By exploiting the presence of positively charged active centers on the Carbopack surface, a stepwise elution system allowed the complete separation of basic/neutral pesticides from acidic ones. After partial solvent removal, the two classes of pesticides were subfractionated and quantified by gradient elution, reverse-phase HPLC with UV detection. The performance of the Carbopack cartridge was compared to that of a 500-mg C-18 bonded silica cartridge. With the Carbopack cartridge, the grand mean measurement accuracy of the 70 analytes was 95.5% with a mean relative standard deviation (RSD) of 1.26%. With the C-18 cartridge, the grand mean measurement accuracy of the analytes was 72.8%, with a mean RSD of 7.91%. Compared to the C-18 cartridge, additional advantages on using a Carbopack cartridge are that the extraction procedure is about seven times shortened, no pH adjustment of the environmental sample is necessary for trapping acidic compounds, one cartridge instead of two suffices to extract basic, neutral and acidic pesticides. The detection limits by this method of all the pesticides considered were between 0.2 and 25 ng/L (signal to noise ratio 3).