Simultaneous Spectrophotometric Determination of Iron (III) and Vanadium (V) in Water Samples Using a Combination of Partial Least Squares Regression and Solid Phase Extraction with Modified Octadecyl Silica Membrane Disks

In this work solid phase extraction had been implemented with fiber optic-linear array detection spectrometry and partial least squares (PLS) multivariate calibration approach for simultaneous determination of ultra trace amounts of metals with complexes which have overlapping spectra. An octadecyl silica membrane disk modified with N-benzoyl-Nphenylhydroxylamine (BPHA) in combination with partial least squares regression (PLS) was used for simultaneous preconcentration and spectrophotometric determination of iron and vanadium in water samples. The method was based on the retention of V(V) and Fe(III) on the disks modified by BPHA in the pH range of 2.0-4.5. The retained ions were eluted with 3 mL of methyl isobutyl ketone and were measured spectrophotometrically. The data obtained from the experiments were processed by partial least squares chemometric method. PLS was applied for multivariate calibration and noise reduction through eliminating of the less important latent variables. Under the optimum conditions, for preconcentrating the analytes from 100 mL sample, the linear dynamic ranges were 14–320 μg L-1 and 10–530 μg L-1 and the detection limits were 4.2 μg L-1 and 2.5 μg L-1 for V(V) and Fe(III), respectively. The method was successfully applied to the determination of analytes in several categories of water samples. The accuracy was assessed through the recovery experiments, independent analysis by graphite furnace atomic absorption spectrometry and the analysis of a certified reference water sample.