Voltammetric determination of iridium(IV) using 5-hydroxyimino-4-imino-1,3-thiazolidin-2-one

Abstract

The influence of the medium acidity on the voltammetric characteristics of the peak of hydrogen catalytic currents in iridium(IV) solutions in the presence of azolidone derivative, viz. 5-hydroxyimino-4-imino-1,3-thiazolidin-2-one was studied. It is shown that the growth of the peak of hydrogen catalytic currents in iridium(IV) solutions in the presence of 5-hydroxyimino-4-imino-1,3-thiazolidin-2-one is observed in the whole studied range of the medium acidity. The optimal conditions were established and the sensitive method for the voltammetric determination of iridium(IV) using the peak of hydrogen catalytic currents was developed (LOD = 1.7×10 -7 M) by means of 5-hydroxyimino-4-imino-1,3-thiazolidin-2-one on the background of 0.3 M sodium chloride at pH 1.00 ± 0.05 (adjusted with hydrochloric acid); scan rate was V = 1 V/s; potentials scan range was E c in . = −0.70 V, E c fin . = −1.50 V; the potential of hydrogen catalytic currents peak was E c p = −1.185 V (relatively to saturated calomel electrode). The developed technique has two intervals of analytical signal linearity, and each of them covers one concentration order (0.3–2.0)×10 -6 M and (0.2–2.0)×10 -5 M. Significant concentration excess of ions of concomitant metals do not interfere the voltammetric determination of iridium(IV), except for the commensurate amounts of Rh(III), Pd(II) and Os(IV); but Ru(IV) and Pt(IV) ions interfere the determination. The significant interfering effect of ions of almost all platinum group elements does not allow us to recommend the developed method for the determination of iridium in samples of natural origin (e.g. rocks, ores, minerals). Instead, the developed technique can be recommended for the analytical control of iridium content in various industrial samples, where it is at the level of microquantities in the absence of other platinum group metals (spark plugs, balls in ballpoint pens, etc.). Keywords: iridium, voltammetric determination, azolidone, oxime.