Permanganometric Titration for the Quantification of Purified Bis(2,4,4-trimethylpentyl)dithiophosphinic Acid in n‑Dodecane

The organic soluble extractant bis­(2,4,4-trimethylpentyl)­dithiophosphinic acid, often called Cyanex 301 (HC301), has shown selectivity for preferentially extracting trivalent actinides over the lanthanides in the treatment of used nuclear fuel. To maintain control and efficiency of a separation process using this extractant, it is necessary to accurately know specific parameters of the system, including the concentration of HC301 in the organic phase, at any given time. Here, the ability to quickly determine the concentration of HC301 in n-dodecane was tested by a one-step permanganometric titration in an organic solution using a double-beam UV–vis spectrophotometer. The addition of HC301 in n-dodecane to solutions of KMnO₄ was found to decolorize the KMnO₄ solutions, but the HC301 was best quantified in terms of decolorization in acetone. This decolorization allowed for the creation of a linear analytical curve relating the amount of KMnO₄ consumed to the amount of HC301 added. Cross-validation of this analytical curve reproduced the known amount of HC301 with an average difference of 1.73% and a maximum of 4.03%.