Determination of imidacloprid in water samples via photochemically induced fluorescence and second-order multivariate calibration

• Photo-induced fluorescence and chemometrics allow determining imidacloprid in water.
• SPE-C18 was applied as a sample preparation step to concentrate the analyte.
• Photoreaction is carried out in 100-μl disposable micropipettes.
• Imidacloprid can be determined in presence of other fluorescent pesticides and dissolved fluorophores.
• The method is satisfactorily compared with the HPLC-DAD method.

This paper presents a new method for the determination of imidacloprid in water samples; one of the most widely used neonicotinoid pesticides in the farming industry. The method is based on the measurement of excitation–emission spectra of photo-induced fluorescence (PIF-EEMs) associated with second-order multivariate calibration with a parallel factor analysis (PARAFAC) and unfolded partial least squares coupled to residual bilinearization (U-PLS/RBL). The second order advantage permitted the determination of imidacloprid in the presence of potential interferences, which also shows photo-induced fluorescence (other pesticides and/or unexpected compounds of the real samples). The photoreaction was performed in 100-μl disposable micropipettes. As a preliminary step, solid phase extraction on C18 (SPE-C18) was applied to concentrate the analyte and diminish the limit of detection. The LOD was approximately 1 ng mL−1, which is suitable for detecting imidacloprid in water according to the guidelines established in North America and Europe. The PIF-EEMs coupled to PARAFAC or U-PLS/RBL was successfully applied for the determination of imidacloprid in different real water samples, with an average recovery of 101±10%.

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