Highly selective catalytic spectrophotometric determination of nanogram amounts of rhenium with N,N-dimethyldithiooxamide in alkaline medium

Abstract

The developed method is based on the catalytic action of Re^IV on the reduction of N,N-dimethyldithiooxamide (DMDTO) with tin(II) in an alkaline medium, yielding a blue coloured product with maximum absorbance at 634 nm. The optimum parameters of the catalytic reaction are described. The calibration graph is plotted at fixed time intervals 10 or 33 min from the addition of tin(II) solution. It is linear in the Re concentration range 2–15 ng ml^–1. A 1000-fold excess of Mo^VI, W^VI, Cd^II, Mn^II, Cu^II, Fe^III, sulfate, silicate, nitrate and ammonia does not interfere with the determination. A modification of the proposed method is used as a rapid spot test. Both methods are applied to the determination of rhenium in molybdenite after alkaline fusion followed by extraction with water. No separation of the matrix is necessary.