Indirect FAAS Determination of Phosphorus in Iron and Steel After Cation Exchange Separation

In dissolution of sample,silicon was expelled as SiF4 by evaporation with HF and HClO4,while phosphorus was oxidized to PO3-4 simultaneously in fuming with HClO4.An aliquot of the sample solution was taken and the orthophosphate in the solution was separated from the matrix Fe(Ⅲ) and other co-existing cations by cation exchange.Eluates from the ion-exchange column were collected in a volumetric flask and the PO3-4 in the solution was precipitated as lead phosphate by reacting with an excess amount of lead standard solution.Content of phosphorus was found indirectly by FAAS determination of excess amount of Pb2+ ion in the filtrate.Linear relationship between values of absorbance and concentration of phosphorus was found in the range within 2.0 mg·L-1,with a detection limit of 5.9 μg·L-1.The proposed method was applied to the determination of 3 standard samples,giving results in consistency with the certified values,and values of RSD′s(n=11) in the range of 1.7%-4.0%.