Analytical Sciences

Multi-Element Analysis of Saline Matrices by Inductively Coupled Plasma Mass Spectrometry Following On-line Preconcentration Using a Knotted Reactor

Fernando A. M. SILVA,* Carmem L. Porto da SILVEIRA,* Norbert MIEKELEY,* and Ivo L. KUECHLER**

*Department of Chemistry, Pontifical Catholic University, 22453-900, Rio de Janeiro, Brazil
**Department of Analytical Chemistry, Fluminense Federal University (UFF), 24020-150, Niterói, Brazil

A versatile preconcentration system for trace element determination by ICPMS was developed. It is composed of a commercial flow injection analysis system (FIAS) retrofitted with a home-made control unit containing three solenoid valves and working concomitantly with the FIAS, permitting selection and segmentation of sample, reagent, washing solution and elution flow. The knotted reactor used had a length of 200 cm and was made from 0.05 cm i.d. PTFE tubing. The method applies ammonium 1-pyrrolidinedithiocarbamate (APDC) as complexant, allowing the preconcentration and quantitative multi-element determination of Cu, Ni, V, Co, Nb, Mo, In, Sb and Bi. Ethanol and 4-methyl-2-pentanone were tested as eluents. Recovery tests using complex matrices and spike concentrations of 200 ng L^-1 showed typical values in the range of 90% to 110%. Relative standard deviations were < 7% for elution with ethanol and < 5% with methyl isobutyl ketone. For simulated freshwater samples using 4-methyl-2-pentanone as an eluent, a sample loading rate of 5.0 ml min^-1, and a preconcentration time of 60 s, detection limits (ng L^-1) were in the range of 0.02 (Bi) to 30 (Cu). Under these conditions, analytical frequency was about 15 samples per hour. The feasibility of the method was demonstrated by the succesful analysis of wastewater and seawater certified reference materials.

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