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 inorganic acids was evaluated and discussed. The study was carried out for 16% HNO3, 28% HCl and a mixture of both acids (aqua regia). It was demonstrated that all electrodeposited. modifiers stabilized cadmium up to 800 degreesC in the presence of HNO3 and aqua regia. When only HCl was present in the solution the thermal stability of cadmium was less pronounced, the maximum pyrolysis temperature that could be applied was 500 degreesC. The long-term study for Cd determination shows that permanent performance of electrodeposited modifiers is not influenced by mineral acids, moreover, the tube lifetime was doubled, compared with a non-modified tube, when Pd + Rh were electrodeposited onto the graphite surface. (C) 2001 Elsevier Science B.V. All rights reserved.