Factor analysis–spectrophotometry for the simultaneous determination of valence states of metals

Abstract

Two Mn+–2-(5-bromo-2-pyridylazo)-5-diethylaminophenol systems for the simultaneous determination of the valence states of Cr and Fe using factor analysis were studied. (1) At pH 4.0, CrIII and CrVI react with the reagent to form stable complexes and a slight difference in the wavelengths of maximum absorption (λmax.) between the two complexes is observed when the sodium lauryl sulfate, which also acts as a solubilizing and sensitizing agent, is added, viz., 590 nm for CrIII and 593 nm for CrVI complexes. (2) In the presence of ethanol, both FeII and FeIII form 1:2 complexes with the reagent at pH 2.5–3.5 and the λmax. of the FeII and FeIII complexes is at 557 and 592 nm, respectively. In the target transformation factor analysis, the K coefficients calculated from the standard mixtures by classical least-squares analysis and a non-zero intercept added to each wavelength are used as the target vector instead of the pure component standards; this can decrease the analysis errors introduced by the interaction between the two species and by deviations from Beer's law.