An intelligent flow analyser for the in-line concentration, speciation and monitoring of metals at trace levels

Abstract

An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents. The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimised physical and chemical variables, linear analytical curves over the ranges 0.025–0.5 or 2.0–40 mg l −1 Fe were attained. The 3 σ detection limit, the repeatability at the 0.5 mg l −1 level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng ml −1 Fe, 2.5%, 58.6 and 22 h −1, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination. A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required.