Determination of Ag, Te, U and Au in waters and in biological samples by FI–ICP-MS following on-line preconcentration

Abstract

An on-line preconcentration system for Au, Ag, Te and U, using solenoid valves, a mini-column filled with C18 immobilized on silica to retain the complexes formed with the ammonium salt of O, O-diethyl dithiophosphoric acid and elution with methanol is proposed. All parameters of the preconcentration, such as sample flow rate, concentration of the complexing agent, acid nature and concentration and elution were optimized. Due to the difficulty of finding compromising conditions for all analytes, they were determined individually. Detections limits ranged from 0.05 to 2.24 pg ml −1 for U and Te, respectively, while the preconcentration factors ranged from 2.6 to 180 for U and Te, respectively. The precision was adequate for the low measured concentrations, with R.S.D. below 10%. Accuracy was assured by the analysis of standard reference enriched water, sea and riverine waters, milk powder, apple leaves and urine, after microwave-assisted digestion of the last three materials. The relatively small volume of methanol, diluted to 1+1, introduced into a conventional nebulizer, minimizes the problems associated with the introduction of organic solvent in the plasma.