Colorimetrically determining total antimony in contaminated waters and screening for antimony speciation

A colorimetric method based on the development of the yellow potassium iodoantimonite complex, previously developed for biological matrices, was applied to successfully quantify total Sb in contaminated waters that were collected from an Sb mineralised zone in NSW, Australia. The method showed good repeatability and little interference from co-occurring ions such as As (III), Ca2+, Fe (III) and SO42−. Field testing demonstrated good precisions and recoveries, making the method truly quantitative under the given conditions. The method's detection limit and limit of reporting (0.6 µg mL−1), made it applicable in areas of high Sb concentration and for rapid response to Sb contamination. Preliminary investigations into extending the method to rapid Sb speciation screening was trialled using anionic SPE columns that retained Sb (V) and excluded Sb (III), in isolation and in combined solutions. Antimony (V) retention was compromised in the presence of ions such as Ca2+ and SO42− spiked at realistic field concentrations. Despite this, the coupling of the colorimetric determination with the anionic columns showed no gross interferences during field trialling, and the columns showed potential for rapid screening of Sb species, as well as rapid preconcentration of Sb from water samples. The latter process lowered the effective detection limit of the colorimetric method almost 10-fold. Both the colorimetric method and the combination of this with rapid speciation techniques show great potential for expanding rapid Sb analysis capability, applicable especially for screening water samples with known or suspected Sb content.