Automated on-line separation–preconcentration system for platinum determination by electrothermal atomic absorption spectrometry

Abstract

A flow injection on-line sorption preconcentration system for the electrothermal atomic absorption spectrometric determination of platinum has been developed. The method employs on-line preconcentration of platinum on a column packed with silica gel functionalised with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-gel) placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 2 M HNO 3, which acts as the elution agent, pass through the microcolumn eluting Pt(IV), which is directly deposited in the graphite tube as a drop of a precisely defined volume. An enrichment factor of 41.7 and a 3 σ detection limit of 0.8 ng ml −1 along with a sampling frequency of 29 h −1 are achieved with 60 s preconcentration time at a sample flow rate of 2.4 ml min −1. The relative standard deviation is 1.6% for 4 ng ml −1 Pt ( n=11). The method has been applied to the determination of platinum in catalyst, vegetation, soil and water samples.