AAS Determination of Iron,Manganese,Zinc,Cadmium in Environmental Water Samples After Enrichment by Coprecipitaion with Cr(Ⅵ)-DDTC

Trace amounts of Fe(Ⅲ),Zn(Ⅱ),Mn(Ⅱ) and Cd(Ⅱ) in environmental water sample was enriched by coprecipitation by DDTC-Cr precipitate.The sample solution (10.0 mL) was adjusted to pH 4.6 with phosphate buffer solution and 150 μL of 20 g·L-1 K2Cr2O7 solution were added to form DDTC-Cr precipitate.One mL of 20 g·L-1 DDTC solution was necessary for complete to precipitation of the 4 elements.The precipitates were separated by centrifugation and dissolved in 2.0 mL of MIBK,which was used for AAS determination.The volume of the MIBK solution introduced for AAS analysis was 300 μL,and Fe(Ⅲ),Zn(Ⅱ),Mn(Ⅱ) and Cd(Ⅱ) were determined by FAAS,while Cd(Ⅱ) was determined by GFFAAS.Under the optimum conditions,values of detection limit (3s/k) found were (μg·L-1) 9.0 (for Fe),6.8 (for Mn),1.8 (for Zn) and 0.03 (for Cd).Values of RSD′s (n=6) found were in the range of 1.8%-3.8% respectively.Recovery was tested on the base of samples of sea water and river water by standard addition method,giving results in the range of 93.7%-105.0%