PRECONCENTRATION OF PALLADIUM, PLATINUM AND RHODIUM BY ONLINE SORBENT EXTRACTION FOR GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY AND INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

A flow system combined with a segmentation technique was used to develop an efficient on-line sorbent extraction preconcentration system for palladium, platinum and rhodium for graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The investigated metals were preconcentrated as their bis(carboxylmethyl)dithiocarbamate (CMDTC) chelates on a microcolumn packed with XAD-4 after the off-line addition of solid CMDTC to the sample solution containing SnCl2 and hydrochloric acid. The sample, rinsing and eluent solutions were segmented by air to prevent dispersion. The eluate was collected on-line in a PTFE loop and was forced either into the graphite tube by nitrogen or into the ICP by using a carrier solution. The time duration of one preconcentration cycle was about 10 min. The influence of the acidity of the synthetic sample solution, the concentrations of the complexing reagent and reducing agent, the flow-rate for preconcentration, the efficiency of the desorption and the influence of various matrices were also investigated. The detection limits (3sigma) were 0.03, 0.1 and 0.01 ng/ml for Pd, Pt and Rh, respectively, using GFAAS detection. The method was applied for the analysis of polluted biological materials.