Simultaneous separation and preconcentration of trace elements in water samples by coprecipitation on manganese dioxide using D-glucose as reductant for KMnO4

A field oriented and economical method of coprecipitation of trace elements like Al, Au, Bi, Cd, Co, Cu, Fe, Mo, Ni, Pb, Pd, Ti, V, W, Zn and REE has been developed. A novel reductant D-glucose, reduces KMnO4 in solution to form a precipitate of MnO2. Two liters of clear natural water sample is adjusted to pH 3.5–4.0, and is treated with 10 ml of 1% KMnO4 and 20 ml of 0.1% D-glucose. The sample is heated at a temperature of 75–80 °C, MnO2 is formed which coprecipitates the above trace elements. The precipitate is separated by filtration, dissolved in 2 ml of 50% HCl and 2 ml of 30% H2O2 and diluted to 25 ml for analysis using AAS and ICP-AES. The recoveries were found to be 96–105%. The preconcentration factor is 80. Limits of determination by the proposed method in natural waters are 1 μg l−1 for Al, Cd, Mo, V, W, Ti and Zn, 5 μg l−1 for Au, Bi, Co, Cu, Fe, Ni, Pb and Pd and 8 μg l−1 for REE. The RSD of the present procedure (n=5) is 8% at ∼5 μg l−1 level. Twenty water samples can be analyzed by an analyst in an 8-h day.