High efficiency low sample consumption on-line ion-exchange pre-concentration system for flow injection flame atomic absorption spectrometry

Abstract

An efficient flow injection system with on-line ion-exchange pre-concentration for the determination of heavy metals by flame atomic absorption spectrometry is described. The system features low sample consumption of only 1.6 ml per determination and a high sampling frequency of 120 h^–1 which is comparable to conventional flame atomic absorption spectrometry. Enrichment factors (EF) of 25–31 (concentration efficiency = 50–62 EF min^–1) were obtained for Cu, Cd and Pb. Relative standard deviations were 1.2–2.8. Low elution flow-rates were used with high nebuliser uptake rates in order to improve the nebulisation efficiency. Conical ion-exchange columns, short, small-bore conduits and three-dimensionally disoriented (3-D) reactors were used to limit the dispersion of the eluted sample zone and/or to improve the precision. Column capacities and elution flow-rates were optimised for the CPG/quinolin-8-ol ion exchanger chosen in order to achieve high enrichment factors and to overcome interferences encountered in sea water analysis.