An optimized sequential extraction scheme for molybdenum association in environmental samples

Abstract

By comparing three sequential extraction procedures, a new optimized extraction scheme for the molybdenum association in environmental samples was proposed. Five operational steps were described as exchangeable (KH2PO4 + K2HPO4: including water-soluble), associated with organic matter (NaOH), Fe–Mn oxides and/or carbonates (HCl), sulfides (H2O2) and residue (HNO3 + HF + H2O2). An optimized extraction scheme was compared with Tessier’s procedure and the Commission of European Communities Bureau of Reference (BCR) was applied to black shales. Results showed Tessier’s procedure gave the lowest concentration values for exchangeable molybdenum and the highest values for the residual molybdenum, which could not present the efficiency of the extraction reagents. BCR’s procedure showed the highest values in oxidizable molybdenum and presented four fractions of molybdenum, which did not demonstrate the fractions of molybdenum in the black shales in detail. The optimized extraction scheme demonstrated a certain improvement on extraction efficiency over Tessier’s procedure for the lowest residual molybdenum, and revealed more featured fraction information of molybdenum in black shales than BCR’s. Therefore, after a comparison with other two extraction procedures, the optimized extraction scheme proved suitable for the molybdenum in black shales and it also showed an accurate determination of the molybdenum in the fractions and source of bioavailable Mo.