Determination of Low Level Concentrations of Metals by Means of Sequential Injection (SI) and Lab-on-Valve (LOV) Methodologies

In recent years sequential injection (SI) analysis and Lab-on-Valve (LOV) approaches have proven themselves as powerful and versatile front ends to implement suitable pre-treatment procedures (separation and pre-concentration) for the assay of low concentrations of metals, as amply reflected in the increasing number of papers appearing in the scientific literature. These novel generations of flow injection analysis have demonstrated themselves as attractive substitutes for labour-intensive, manual sample pre-treatment and solution handling methods prior to analyte detection by atomic absorption/emission spectrometric devices such as FAAS, ETAAS, AFS, ICP-AES, and ICP-MS. While earlier separation and pre-concentration schemes of metals in liquid samples primarily have been centred on the use solvent extraction, or precipitate/(co)-precipitate collection in incorporated knotted reactors, or permanent columns packed with suitable materials, the emphasis in this lecture will be on applying solid-phase extraction in the SI/LOV mode. Providing unique characteristics and specific advantages, particularly allowing to take advantage of the so-called renewable approach, where the solid-phase material, if called for, can be replaced for each analytical cycle via the bead-injection concept, a number of examples will be given, comprising both the determination of various metals and also its use for speciation procedures. Recently, these miniaturised methodologies have also been shown to constitute appealing options to handle solid samples of environmental interest as demonstrated by the accommodation of both single and sequential extraction schemes for metal fractionation of solid samples of environmental concern (e.g. soils and sediments) packed within dedicated microcartridges. A brief account of the construction and the experimental modes of operandi of this novel approach for executing metal extraction/fractionation schemes will, to the extent that time allows it, also be given.