Abstract
The paper describes the development of an automatic on-line column pre-concentration technique using a time based-flow injection atomic absorption spectrometry system. A manifold incorporating a micro-column containing 25 mg of Dowex 50W-X8 was used with a time-based injector for the pre-concentration and determination of copper in natural and drinking waters. The system features depend on the alternate positions of a solenoid valve. The 3σ detection limits, enrichment factors, sampling frequency, relative standard deviations and linear calibration graphs were, respectively, in the range 0.6-1.5 μg/l, 25-60, 15-30 measurements/h, 1.0-3.1% and 1-65 μg/ml for pre-concentration times of 1 min. The procedure was successfully applied to a range of water samples and the accuracy was assessed through recovery experiments, the analysis of certified reference water samples and by independent analysis by atomic absorption spectrometry with electrothermal atomization.
Highlights
Ion exchangers used in miniature columns have proven useful for both analyte concentration and the removal of interfering compounds
The conventional column mode of ion-exchange pre-concentration is both tedious and time consuming compared with the final rapid determination of atomic spectroscopy (AS) techniques [1]
This paper reports on an attempt to develop a fully automated on-line system with an electronically operated time-based injector tbr high efficiency, low sample and reagents consumption ion-exchange pre-concentration
Summary
Ion exchangers used in miniature columns have proven useful for both analyte concentration and the removal of interfering compounds. The use of ion exchange as an auxiliary technique with flow injection (FI)-AS results in on-line increased sensitivity with respect to the direct aspiration procedure, speeding up and simplying the pre-concentration step and the implementation of simultaneous determinations and/or speciation [2]. And electronically operated injection and pneumatic valves and commutators have been employed for sample introduction in ion exchangers--FI-AAS manitblds [3, 4]. These introduction devices permit the reproducible and sequential introduction of defined sample volumes into flowing systems, but they are wasteful in terms of the sample. The FI-AAS system described was designed for the determination of copper at the sub-gg/ml level in water
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