Simultaneous determination of urea herbicides in water and soil samples based on second-order photoinduced fluorescence data

Abstract

This work presents an innovative strategy for the simultaneous determination of four widely employed urea-derivative herbicides, namely isoproturon, linuron, monuron and rimsulfuron, in interfering environments, combining second-order photoinduced fluorescence (PIF) signals, obtained upon UV irradiation in micellar aqueous solutions, and multivariate calibration. The method is simple and fast and complies with the green analytical chemistry principles because it avoids the consumption of high amounts of organic solvents. Successful results were obtained by measuring excitation–emission photoinduced fluorescence matrices processed with unfolded partial least-squares/residual bilinearization (U-PLS/RBL) algorithm. Indeed, this algorithm allowed us to achieve selectivity even in a system which shows a significant spectral overlapping among the formed photoproducts. The quality of the proposed method was evidenced on the basis of the analytical recoveries from water and soil samples spiked with analytes. After solid-phase extraction, reaching a pre-concentration factor of 250, detection limits ranging from 0.006 to 0.026 ng mL⁻¹ were obtained in water samples. In soil samples, the detection limits ranged from 1.1 to 3.3 ng g⁻¹ without a pre-concentration step. The relative prediction errors were lower than 7% in both cases.