W+Rh as permanent chemical modifier in simultaneous atomic absorption spectrometry: interference studies on As, Cd, Pb and Se determination

a systematic study of na+, k+, ca2+, mg2+, cl-, no3-, so42- and po43- interference on the simultaneous atomization of as, cd, pb and se was carried out using an electrothermal atomic absorption spectrometer. the mixture 250 mg w + 250 mg rh was thermally deposited on the graphite tube platform and used as permanent chemical modifier. the compromised heating program adjustments (tp = 650ºc and ta = 2200ºc) diminished the thermal decomposition and volatilization efficiency of the interfering species during the pyrolysis step. the cl- and so42- anions caused the most severe interference, while no3- only affected the analytes' atomization when high amounts (> 27 mg) were used. the anion po43- produced a strong negative interference on the se absorbance signals. the presence of na+, k+, ca2+ and mg2+ prejudiced mainly cd, and the interference effects of cl- salts were more pronounced than no3- salts.