Optimisation of flow-injection-hydride generation inductively coupled plasma spectrometric determination of selenium in electrolytic manganese.

Flow-injection-hydride generation procedure for Se in electrolytic manganese was optimized by means of the experimental design approach. Instrumental variables like power supplied (P), sample (F) and argon (G) flow rates together with chemical variables like NaBH(4) and HCl concentrations were studied. In case of the chemical variables, it was concluded that sodium tetrahydridoborate concentrations higher than 1.0% extinguished the plasma while HCl concentration should always be higher than 0.6moldm(-3). The analysis of effects suggested that all the instrumental variables are significant factors, and the optimum conditions were P=1550W, F=4.75mLmin(-1) and G=0.6mLmin(-1). The influence of Mn was specially studied and it was concluded that the interferences were negligible if Mn is below 2.0gL(-1). In the same sense, the interferences of antimony(III), arsenic(V) and mercury(II) were also considered negligible. Finally, a detection limit of 0.0005% (w/w) was obtained (a repeatability R.S.D. <2.0% for all Se concentrations tried). Some manganese samples were also spiked with different concentrations of Se(IV) and the results demonstrated to be in good statistical agreement with expected values.