Simultaneous determination of palladium, platinum and rhodium by on-line column enrichment and a rapid column high performance liquid chromatography with 2-carboxyl-1-naphthalthiorhodamine as precolumn derivatization reagent

In this paper, 2-carboxyl-1-naphthalthiorhodamine (CNTR) was synthesized, and a new method for the simultaneous determination of palladium, platinum, and rhodium ions as metal-CNTR chelates was developed using rapid column high performance liquid chromatography combined with on-line enrichment. The palladium, platinum, and rhodium ions were precolumn derivatized with CNTR to form colored chelates. The Pb-CNTR, Pt-CNTR, and Rh-CNTR chelates could be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column (ZORBAX Stable Bound, 4.6x10 mm, 1.8 mu m) with a buffer solution of 0.05 mol/L sodium acetate-acetic acid buffer solution (pH 3.5) as mobile phase. After enrichment, and by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. The separation of these chelates on the analytical column (ZORBAX Stable Bound, 4.6x50 mm, 1.8 mu m) was satisfactory with 54% methanol (v/v) in 0.05 mol/L sodium acetate buffer (pH 3.5) containing 1 g/L Triton X-100 as mobile phase. Palladium, platinum, and rhodium were separated completely within 2 min. The detection limits (S/N=3) of palladium, platinum, and rhodium are 1.4 ng/L, 1.2 ng/L, and 1.8 ng/L, respectively. This method was applied to the determination of palladium, platinum, and rhodium in water, urine, and soil samples with good results.