Performance of electrodeposited noble metals as permanent modifiers for the determination of cadmium in the presence of mineral acids by electrothermal atomic absorption spectrometry

The analytical performance of electrodeposited noble metals (Pd, Rh or Pd Rh) on the graphite surface for cadmium determination in the presence of i norganic acids was evaluated and discussed. The study was carried out for 1 6% HNO3, 28% HCl and a mixture of both acids (aqua regia). It was demonstra ted that all electrodeposited. modifiers stabilized cadmium up to 800 degre esC in the presence of HNO3 and aqua regia. When only HCl was present in th e solution the thermal stability of cadmium was less pronounced, the maximu m pyrolysis temperature that could be applied was 500 degreesC. The long-te rm study for Cd determination shows that permanent performance of electrode posited modifiers is not influenced by mineral acids, moreover, the tube li fetime was doubled, compared with a non-modified tube, when Pd + Rh were el ectrodeposited onto the graphite surface. (C) 2001 Elsevier Science B.V. Al l rights reserved.