Lab-on-Valve Micro Sequential Injection: A Versatile Approach for Implementing Integrated Sample Pre-preparations and Executing (Bio)Chemical Assays

Since its introduction in 1975, Flow Injection Analysis (FIA) has established itself as an indispensable analytical concept that not only has permitted the implementation of numerous intriguing analysis procedures. But, more importantly, it has made it possible to facilitate the execution of procedures which are difficult or, in fact, otherwise impossible to do, thereby opening new and novel avenues for analytical methods relying on concepts such as kinetic discriminations schemes, exploitation of metastable constituents of attractive analytical characteristics, or utilisation of detection by bio- and chemiluminescence. In recent years, FIA has been supplemented by Sequential Injection Analysis (SIA), which, although it inherently entails some limitations as compared to FIA, offers specific advantages, notably in terms of significantly reduced sample and reagent(s) consumption and hence waste generation. Most recently, the socalled third generation of FIA has emerged, that is, the Lab-on-Valve (LOV) approach, the conceptual basis of which is to incorporate all the necessary unit operational manipulations required, and, when possible, even the detection device into a single small integrated microconduit, or “laboratory”, placed atop a selection valve. The lecture will detail the evolution of the three generations of FIA, emphasis being placed on the LOV approach. Proven itself as a versatile front end to a variety of detection techniques, its utility will be exemplified by a series of applications. Particular focus will be placed on its use as a vehicle for pretreatment of complex sample matrices for determination of trace-level concentrations of metal ions by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS) via exploitation of the renewable microcolumn concept. Despite their excellent analytical chemical capabilities, ETAAS as well as ICPMS often require that the samples are subjected to suitable pretreatment in order to obtain the necessary sensitivity and selectivity. Either in order to separate the analyte from potentially interfering matrix constituents, or to preconcentrate the analyte material to bring it into the dynamic range of the detector. As will be shown, such pretreatments are advantageously performed in FIA/SIA/LOV manifolds, where all appropriate unit operations can be effected under enclosed and strictly controlled conditions.