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 microw ave assisted desorption is proposed for the efficient flame atomic absorpti on spectrometric determination of trace amounts of Pt. A microcolumn packed with thiourea modified silica gel placed in a microwave oven was used to c ollect Pt from sample solutions. 2% thiourea was used to elute the adsorbed Pt into the nebulizer of the spectrometer with microwave irradiation. Opti mization studies were carried out on the volume of cooling water, heating t ime of the microwaves, sample acidity, concentration of eluent etc. Common co-existing ions did not interfere with the determination of Pt(IV). The RS D of determination of 1.0 mu g ml(-1) was < 4% with 120 s of preconcentrati on at a sampling flow rate of 2.5 ml min(-1). The limit of detection, defin ed 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 met allurgical samples, a secondary nickel alloy, anode slime and a CoCl2 solut ion, were in good agreement with the recommended values.