DETERMINATION OF TRACE-METALS IN SODIUM DITHIONITE-CITRATE EXTRACTS OF SOILS AND SEDIMENTS BY ATOMIC-ABSORPTION

The oxides of iron and manganese and their occluded trace elements are readily dissolved with a strong reducing agent such as sodium dithionite. Precipitation and (or) sorption onto containers is minimized by the presence of citrate. the trace metals, and most of the iron present in suitable aliquots, are extracted with APDC into MIBK for analysis by atomic absorption of spectrophotometry. Since iron causes some interferences in the determination of trace elements by atomic absorption, the aliquot size is varied to give a constant quantity of iron in the organic solvent. The actual quantity of these trace elements varied considerably among samples. It is concluded that occluded organics released during the oxide reduction treatment will have a negligible effect on trace element recovery in the organic solvent.