Simultaneous determination of arsenic and antimony in steels and pure coppers by high power nitrogen microwave induced plasma atomic emission spectrometry coupled with hydride generation technique

The feasibility of an annular-shaped high power nitrogen microwave induced plasma atomic emission spectrometry (N-2-MIP-AES) has been studied for the simultaneous determination of arsenic and antimony in combination with the hydride generation method. Under the optimized experimental conditions, the best attainable detection limits at As I 228.812 and Sb I 231.147 nm lines were 4.13 and 4.50 ng/ml for arsenic and antimony, respectively, with a linear dynamic range of 10 to 10,000 ng/ml in concentrations, The presence of several diverse elements was found to cause more or less a depressing interference by the proposed technique. Of the several pre-reductants examined, thiourea was found to be the most preferable to reduce arsenic and antimony from their pentavalent state to trivalent one prior to hydride generation. Therefore, thiourea was utilized as a pre-reductant for the determination of total arsenic and antimony concentration, i.e., As(III) + As(V) and Sb(III) + Sb(V). When arsenic and antimony in steels were determined simultaneously, a large amount of Fe(III) in the solution caused a severe depressing interference, while the presence of Fe(II) showed little or no significant interference, Of the several interference-releasing agents examined, both thiourea and L-ascorbic acid were found to be the most preferable to reduce Fe(III) to Fe(II). When arsenic and antimony in high purity coppers were determined simultaneously, copper of principal constituent interfered to a great extent. Thiourea was found to reduce the depressing interference from copper, so that any separation procedure of copper matrix was not necessary. The proposed method using thiourea not only as a pre-reductant but also as an interference-releasing agent was applied to the simultaneous determination of low concentrations of arsenic and antimony in carbon steels and high pure coppers. The results obtained by this method were in good agreement with the certified values.