Liquid-liquid extraction of ruthenium(III) thiocyanate with hexamethylphosphoramide: Direct spectrophotometric determination in the organic phase

Abstract

Ru(III)-thiocyanate has been extracted with hexamethylphosphoramide (HMPA) in methyl isobutyl ketone (MIBK). Thus the extractability, sensitivity and selectivity are improved over the simple binary Ru(III) thiocyanate system in spectrophotometric determination of ruthenium in the organic phase. The maximum colour develops on the steam bath, at the acidity range of 1.5–2.5M with HCl and ammonium thiocyanate concentration range of 0.25–0.5M. The colour is completely extractable in MIBK when 1.5–3.0 ml HMPA is used and show maximum absorbance at 570 nm. The colour system obeys Beer's law for 0.7–13 νg Ru/ml and the optimum concentration range is 2–13 νg/ml. The molar absorptivity and sensitivity are 69401-mole−1 cm−1 and 0.0145 νg/cm2 respectively. The percent relative error is 2.72%. The method is very simple and does not require oxidation and subsequent distillation. The method can be applied in the presence of osmium.