Technical communication: Determination of cuprous ions in bacterial leachates and for environmental monitoring

A sensitive and precise spectrophotometric method has been developed for the determination of copper(I) in bacterial leach liquors produced by the action of Thiobacillus ferrooxidans and T. thiooxidans on copper ores. In this method bicinchoninic acid (BCA) has been used as the chromogenic reagent which produces a stable purple complex with Cu(I) which was found to obey Beer's Law and with lambda(max) at 560 nm. The coloured complex has a molar extinction coefficient (epsilon) value of 6.6 x 10(3) l mol(-1) cm(-1); specific absorptivity (alpha) value of 0.104 ml(-1) g cm(-1) and the Sandell sensitivity (S) value was 0.0096 mu g cm(2). Optimal conditions for development of coloration/sensitivity were determined. Interferences due to cations and anions were investigated and various masking agents for alleviating their inhibition were studied. The method has been found very useful in determining ratios of Cu(I) to Cu(II) in bacterial leach liquors and should play a significant role in determining the reaction mechanisms of biological leaching and for environmental monitoring.