Extraction spectrophotometric determination of trace amounts of perchlorate based on ion-pair formation with thionine

A simple, rapid, and sensitive extraction-spectrophotometric method has been developed for the determination of trace amounts of perchlorate. This method is based on the extraction of perchlorate as an ion pair with thionine into isobuthyl methyl ketone and measuring the absorbance of the organic phase at 603 nm. The effect of different variables such as pH, reagent concentrations, and standing time was investigated and optimum conditions were established. The effects of other cations and anions on the extraction were also studied. The calibration curve was linear in the range of 40-1000 ng mL(-1) with correlation coefficient of 0.9998. The detection limit based on 3S(b) criterion was 23 ng mL(-1) and the relative standard deviation for 400 ng mL(-1) of perchlorate was 1.9%. The proposed method was applied to determination of perchlorate in water samples.