Assessment of FTIR spectrometry for pesticide screening of aqueous samples

This article assesses the potential of Fourier transform infrared spectrometry (FTIR) to be used in pesticide screening and determination of selected pyrethroid and organochlorine pesticides in fresh water. FTIR spectra of 28 single pesticides in the dry state were recorded on a horizontal diamond attenuated total reflection (ATR) element. Hierachical cluster analysis of the recorded FTIR spectra (spectral range: 4000-500 cm(-1)) showed that different pesticide groups could be distinguished. A representative of each main group (dichlofuanid. captan and fenpropathrin) was selected and their direct simultaneous determination in fresh water without using a chromatographic separation step investigated. The developed analysis procedure comprised a liquid-liquid extraction step with n-hexane, further automated clean-up and preconcentration by solid-phase extraction using a silica mini-column and final elution of the analyte with ethyl acetate. The extract containing the analytes was further concentrated and dried on the ATR element for spectrum acquisition. Using a partial least square (PLS) calibration it could be shown that all three analytes could be quantified in fresh water in a concentration range from 1.2 to 4.8 mug/L. Recoveries for dichlofuanid, captan and fenpropathrin from fortified tap and river waters ranged from 66.3 to 102.0% (captan was the pesticide providing the lowest values, 66.3 and 70.3%).