Simultaneous determination of Fe(III) and Al(III) by first-derivative spectrophotometry and partial least-squares (PLS-2) method - Application to post-haemodialysis fluids

Derivative spectrophotometry (graphical method) and partial least-squares regression (numerical method) methods were developed for the spectrophotometric multi-component analysis of post-haemodialysis fluids and synthetic mixtures containing Al(III) and Fe(III) without any chemical separation. The complexes of these metal ions with chrome azurol S were formed immediately Lit pH 5.5 and were stable for Lit least 3 h. The graphical method is based oil the use of first-derivative spectral for evaluation because working wavelength determination was more precise and Spectral overlap was less than III the ordinary spectra. Two wavelengths Lit which the complexes exhibited maximum absorption values for Fc(III) and Al(III) were selected as analytical wavelengths, i.e.. 675 and 623.5 nm. respectively. Lambert-Beer's law is obeyed between 0.0896-8.064 mu g/mL Fe(III) and 0.054-0.486 mu g/mL Al(III). Limits of detection for Fc(III) and Al(III) were 0.056 and 0.044 mu g/mL, respectively. The reproducibility, expressed Lis variation coefficients, for two sets of 10 standard mixtures containing 3.584 mu g/mL Fc(III) and 0.27 mu g/mL Al(III) were 1.9% and 2% for iron and aluminium, respective. In the numerical method, a training set was randomly prepared by using 14 samples. The concentration of each component has been varied in the linear ran-c of the analytical signal. The spectral regions between 5 10 and 720 nm were selected for the analysis of the binary mixture of Fe(III)/Al(III). The proposed methods were validated by Using synthetic binary mixtures and applied to the simultaneous determination of Fe(III) and Al(III) in post-haemodialysis samples. The obtained results were compared with each other: in general, both multi-component methods gave rise to similar recovery results for laboratory-prepared mixtures and real samples. (C) 2008 Elsevier GmbH. All rights reserved.