Microcolumns MSFIA-microcolumn

In an attempt to integrate all the analytical process in a single device, a hyphenated MSFIA-microcolumn semp has been assembled for automated flow-through partitioning and accurate determination of the content of bioavaUable forms of orthophosphate in soils and sediments utilizing the molybdenum blue method for extract processing [103]. 

Different procedures based on that chemistry and using FIA [183], SIA [166,184], MSFIA [185,186], and MCFIA [187] have been described. Most of them make use of online sample preparation, including micellar-assisted preconcentration (cloud point extraction (CPE)) or solid-phase extraction (SPE) [185,186,188]. To this end, either a microcolumn packed with Amberlite XAD-4 resin [185] or C18-modified silica material may be used. 

Online sorptive preconcentration exploiting renewable solid surfaces, the so-called bead injection (Bl), in the miniaturized LOV platform has been hyphenated to GC separation with electron-capture detection for automated determination of trace levels of PCBs in solid-waste leachates. To this end, the MSFIA system presented in Chapter 3, Figure 3.19, has been implemented. It comprises a mul-tisyringe burette, an extra solenoid valve, an LOV, and an injection valve (IV) as well as reversed-phase copolymeric beads with hydroxylated surface (Bond Elut Plexa) included into the channels of a poly(ether imide) LOV microconduit, thus serving as a transient microcolumn-packed reactor for preconcentration of organic species [194]. 

Beads packed in microcolumns is the most reported in literature, since users can customize the quantity of resin according to the capacity of it, to the volume of sample to be loaded, and to the minimum detectable activity (MDA) of the detector used. In general, packing is manually replaced in flow systems based on flow injection analysis G A), sequential injection analysis (SIA), multisyringe flow injection analysis (MSFIA) and multipumping flow systems (MPFS). By the contrary, lab on valve (LOV) allows the manipulation of heterogeneous solutions, i.e. bead injection, achieving the automated replacement of the resin. In Chapter 3 are described in detail the parts of the microcolumns and the way to fill them. Table 8.1 summarizes the variety of available resins from TrisKem International [4]. 

FIGURE 1,10 Schematic diagram of the hybrid flow-through microcolumn extraction/ multisyringe flow injection analysis (MSFIA) system for fractionation and online determination of orthophosphate. SP—syringe pump, MSP—multisyringe pump, SV— selection valve, V—solenoid valves, KR—knotted reactors, D—detector. (Adapted from Buanuam,]. et al. 2007. Talanta 71 1710-1719.)... 

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