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 substantial number of papers that have emerged 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 spectrometry (FAAS, ETAAS, ICP-AES, ICP-MS). The lecture will initially give an overview of various automated alternatives for facilitating appropriate SI/LOV-separation and pre-concentration schemes of metals in liquid samples, including examples of solid-phase extraction with permanent columns or renewable surfaces via the bead-injection concept, solvent extraction-back extraction, and molecular sorption and precipitate/(co)-precipitate collection onto the walls of knotted reactors. 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. An account of the construction and the experimental modes of operandi of this novel approach for executing metal extraction/fractionation schemes will be given, while a detailed discussion of the ecotoxicological relevance of the data thus provided, and set into context with other fractionation methodologies, will be offered in a separate presentation given by the second author.