Extraction and preconcentration of Cr(VI) from urine using supported liquid membrane Original Research Article

A supported liquid membrane (SLM) technique was investigated to extract and preconcentrate Cr(VI) from urine. Methyltricaprylammonium chloride (aliquat 366) with kerosene as diluent was used as a carrier in the membrane to transport Cr(VI) from the donor side to acceptor side. The membrane was modified with tri-n-butylphosphate (TBP) to increase its polarity. Various parameters were investigated to optimize the extraction efficiency: pH of the donor and acceptor phase, dilution factor, donor flow rate, boiling the sample and treatment with acetonitrile. Scanning electron microscope pictures of the membranes revealed that some matrix compounds were deposited on the surface, thus, limiting the extraction process. This was minimized by treatment of the urine sample with acetonitrile. The optimum conditions found were: pH 3 in the donor phase, sodium nitrate in the acceptor phase, donor flow rate of 0.3 ml min−1, 5% (w/v) aliquat in kerosene as a carrier in membrane, and 20 times the dilution factor. The extraction efficiency was found to be 15% with different concentrations of Cr(VI) standard addition extracted and shows that the method is highly reproducible. The adsorptive stripping voltammetry (AdSV) was used to determine Cr(VI) concentration. The optimized method was used to determine the concentration of Cr(VI) in urine samples of chromium smelter workers.