On-line preconcentration and flow analysis–Fourier transform infrared determination of carbaryl

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Abstract
A new strategy to improve the limits of detection in Fourier transform Infrared (FTIR) has been developed. The proposed method consists of preconcentration of samples, using conventional solid phase extraction cartridges, and online elution with dichloromethane. Absorbance measurements are obtained by FTIR. Carbaryl has been used as a test molecule with on-line measurements carried out at 1746 cm–1. This procedure permits (i) field sampling, (ii) stabilization of pesticides, and (iii) fast determination of carbaryl in the laboratory. The sensitivity obtained with this procedure corresponds to 0.0444 area units µg–1 cm–1, and the limit of detection, to 15 µg of carbaryl, which, for a sampling volume of 11, corresponds to 15 µg l–1 of this pesticide. The reproducibility of three independent analyses of a well water sample containing 195 µg l–1 of carbaryl corresponds to a relative standard deviation of 8.6%.