Simultaneous determination of pesticides at trace levels in water using multiwalled carbon nanotubes as solid-phase extractant and multivariate calibration

The application of solid-phase extraction with multivariate calibration for simultaneous determination of three toxic pesticides in tap and reservoir waters was presented. The proposed analytical method was used for the determination of atrazine, methidathion, and propoxur in complex water samples without the need for chromatographic separation. Among the applied multivariate calibration methods, partial least squares (PLS-1) method was found the most effective for pesticides quantification. Multiwalled carbon nanotubes (MWCNTs) adsorbent showed a perfect extraction/preconcentration of pesticides present at trace levels. The experimental factors that affect pesticides extraction by MWCNTs adsorbent such as sample volume, eluent volume, solution pH, and extraction flow rate were studied and optimized. The figures of merit of the proposed method were: limits of detection 3, 2, and 3 μg l−1 and linear ranges 5-30, 3-60, and 5-40 μg l−1 for atrazine, methidathion, and propoxur, respectively. A good precision was reported for the method, R.S.D. values were always less than 5.0%. Satisfactory results were reported for simultaneous determination of trace levels of pesticides in complex matrices. In tap water, the percent recoveries for pesticides were extended from 95 to 104% and R.S.D. from 1 to 3%, while lower recoveries were observed in reservoir water: 84-93% (R.S.D.: 1-3). Although the pesticides can be accurately quantified by SPE and liquid chromatography, SPE-PLS-1 method was found simpler and operated at lower running costs.