FLOW-INJECTION ONLINE SORPTION PRECONCENTRATION OF PLATINUM IN A KNOTTED REACTOR COUPLED WITH ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A flow injection on-line sorption preconcentration method for the elec trothermal AAS determination of platinum has been developed. The pyrro lidine dithiocarbamate complexes of either Pt4+ or Pt2+, formed in 0.7 mol L-1 HNO3, are on-line adsorbed on the inner walls of a PTFE knott ed reactor and subsequently eluted with methanol. An enhancement facto r of 112 and a detection limit (3 sigma) of 10 ng L-1 along with a sam pling frequency of 21 h(-1) are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mt min(-1). The relative standard de viation is 2.5% for 0.4 mu g L-1 Pt. The method has been applied to th e determination of platinum in blood samples.