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

An on-line preconcentration system for Au, Ag, Te and U, using solenoid val ves, a mini-column filled with Cls immobilized on silica to retain the comp lexes formed with the ammonium salt of O,O-diethyl dithiophosphoric acid an d elution with methanol is proposed. All parameters of the preconcentration , such as sample flow rate, concentration of the complexing agent, acid nat ure acid concentration and elution were optimized. Due to the difficulty of finding compromising conditions for all analytes, they were determined ind ividually. Detections limits ranged from 0.05 to 2.24 pg ml(-1) for U and T e, 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 analysi s of standard reference enriched water, sea and riverine waters, milk powde r, apple leaves and urine, after microwave-assisted digestion of the last t hree 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. (C) 2001 Elsevier Science B.V. All rights reserved.