Exploiting second-order advantage for simultaneous and interference-free determination of orthophosphate and arsenate in water samples

A novel approach for the simultaneous determination of orthophosphate and arsenate as a vital parameter for environmental controlling was developed using the molybdenum blue method. The second-order chemometrics analysis was employed to overcome significant spectral overlapping among analytes and interferences. Two powerful second-order calibration methods including, Bilinear least squares/residual bilinearization (BLLS/RBL) and Parallel factor analysis (PARAFAC) methodologies, were used for analysing kinetic-spectroscopic second-order data and the decomposition of spectra and quantification of analytes. These methodologies are capable of accurate and reliable discernment of the target analyte signals, even in the presence of unknown and uncalibrated interferences, which are inherently capable of providing the second-order advantage. No sample pretreatment or separation steps were required. The proposed method was performed on the water samples, and the accuracies of both methods were successfully validated by the analytical figures of merit (FOM). The limits of detection (LOD) were 0.28 and 0.29 mu mol L-1 using BLLS/RBL method and 0.14 and 0.16 mu mol L-1 using PARAFAC method for orthophosphate and arsenate, respectively. Orthophosphate and arsenate recoveries in real water samples were determined between 97.0 and 100.5% using both methods.