On-line preconcentration and separation of platinum using thiourea modified silica gel with microwave assisted desorption for FAAS determination

A flow-injection on-line preconcentration and separation system with microwave assisted desorption is proposed for the efficient flame atomic absorption spectrometric determination of trace amounts of Pt. A microcolumn packed with thiourea modified silica gel placed in a microwave oven was used to collect Pt from sample solutions. 2% thiourea was used to elute the adsorbed Pt into the nebulizer of the spectrometer with microwave irradiation. Optimization studies were carried out on the volume of cooling water, heating time of the microwaves, sample acidity, concentration of eluent etc. Common co-existing ions did not interfere with the determination of Pt(IV). The RSD of determination of 1.0 mu g ml(-1) was < 4% with 120 s of preconcentration at a sampling flow rate of 2.5 ml min(-1). The limit of detection, defined as three times the standard deviation of blank (3 sigma), was 0.060 mu g ml(-1). The results obtained by the proposed method for three types of metallurgical samples, a secondary nickel alloy, anode slime and a CoCl2 solution, were in good agreement with the recommended values.