ICP-OES Monitoring of the Instability of [OsCl6]2− and Evaluation of [OsO2(CN)4]2− as Alternative Standard for Osmium Quantification

Abstract

Abstract A spectrometric method using inductively coupled plasma optical emission spectrometry (ICP-OES) for the determination of Os and the stability of (NH4)2[OsCl6] standard was developed. Results obtained from this study showed a gradual decrease in Os recovery in the liquid reference material (RM) within 96 h of having prepared the calibration standards. The instability of the Os standard (NH4)2[OsCl6] resulted in the decrease in Os percentage recoveries. The Os calibration plots shifted (gained or lost sensitivity) after every 24 h. This gain or loss in sensitivity also varied, depending on acid or base used. In acidic medium, the gain in sensitivity of the calibration curves increased from HCl < HBr < HF whilst in the basic medium, the calibration plots decreased in sensitivity from NaOH < KOH < NH4OH. The stable Cs2[OsO2(CN)4] compound was synthesized and evaluated for its suitability as osmium standard and it was determined to be a good alternative standard for Os analysis due to its excellent stability in HCl matrix and at room temperature. The optimum storage conditions for both Os standards (NH4)2[OsCl6] and Cs2[OsO2(CN)4] and the liquid RM analyte solutions were in the acidic medium (HCl), in the dark and at ca. 10 °C.