Simultaneous determination of the pesticide naptalam and its metabolites in natural water by Fourier transform infrared spectrometry

Abstract

A new strategy was developed to improve the limits of detection in Fourier transform infrared (FTIR) spectrometry for the simultaneous determination of the pesticide naptalam, N-(1-napththyl)phthalamic acid (NAP), and its metabolites, 1-naphthylamine (NNA) and N-(1-naphthyl)phthalimide (NPhDA), in natural water. The proposed method consists of preconcentration of samples using conventional C₁₈ solid-phase extraction (SPE) discs, subsequent elution with methanol and dissolution of the residues in dimethyl sulfoxide after vaporization of the extract, absorbance measurements by FTIR in the spectral region 1500–1800 cm^–1 and prediction of concentrations of the components in recovered solutions using the partial least squares calibration model. The SPE recoveries for NAP, NNA and NPhDA were 98 ± 4, 94 ± 3 and 96 ± 3%, respectively. The detection limits of the proposed coupled SPE-FTIR method for NAP, NNA and NPhDA in water samples were 111, 72 and 90 ppb, respectively.