Simultaneous determination of vanadium(IV) and vanadium(V) by flow injection analysis using kinetic spectrophotometry with Xylenol Orange.

A flow injection method of analysis has been developed for the simultaneous determination of V(IV) and V(V) using the difference in the rate of complex formation between vanadium in two different oxidation states and Xylenol Orange in acidic media. The proposed method used a spectrophotometric detector equipped with two flow cells aligned with the same optical path to yield two successive peaks per each sample injection. V(IV) and V(V) were determined by solving simultaneous equations in two unknowns, the concentrations of V(IV) and V(V), obtained from measurements of the two peak heights.

Flow-injection simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on photochemical reactions of thiocyanato-complexes.

The flow injection analysis systems have been developed for the simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on the photochemical reactions of their thiocyanato-complexes. In the first system, a sample solution was injected in to nitric acid solution and mixed with ammonium thiocyanate solution, followed by spectrophotometric monitoring of the thiocyanato-complexes formed. Another aliquot of the same sample solution was injected and the thiocyanato-complexes formed in the same way were irradiated by UV light before spectrophotometric monitoring.