Multicommutated flow analysis

Three-way solenoid valve. (For color version of this figure, the reader is referred to the online version of this book.) 

Schematic depiction of a typicai MCFiA system. RC reaction coil, V valve. 

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Computer-controlled systems are applied in other techniques derived from FIA, such as sequential injection analysis (SIA, introduced in 1990), multicommutation flow analysis (MCFA, introduced in 1994), and multisyringe flow injection analysis (MSFIA, introduced in 1999). 

East-switching three-way solenoid valves constitute the technical basis of the multicommutated flow analysis technique and also are common elements of multisyringe flow injection analysis systems. We... 

On the other hand, advances in information technology have provided most salient flow techniques benefits, such as fully automation, autonomy, precision and accuracy. Therefore, advances in more recent techniques such as SIA, multicommutated flow analysis (MCFIA), multisyringe flow injection analysis (MSFIA) and lab on valve (LOV), and their combinations, have relied on the availability of appropriate dedicated software for their control. 

Tymecki, L., K. Strzelak, and R. Koncki. 2013. Biparametric multicommutated flow analysis system for determination of human serum phosphoesterase activity. Anal. Chim. Acta 797 57-63. 

Fernandes, E. N. and B. F. Reis. 2006. Automatic spectrophotometric procedure for the determination of tartaric acid in wine employing multicommutation flow analysis process. Anal. Chim. Acta 557(1—2) 380—386. 

In recent years, many flow systems consisting of several pumps (multipump flow systems) or several injectors (multicommuted flow systems) have been constmcted and exploited. Some of them are dedicated to calibration purposes. For instance, the standard addition method was recently implemented using a multicommuted system with an injection valve and three directive solenoid valves [7]. The system can automatically prepare a series of calibration solutions by successively merging a sample with three standards of different analyte concentrations. The approach is especially suitable for trace analysis because, according to the author s recommendation, it can be used when the analyte concentration in the sample is below the lower limit of linear response of a detector (it allows, in particular, potentiometric... 

B.F. Reis, M.F. Gine, E.A.G. Zagatto, J.L.F.C. Lima, R.A.S. Lapa, Multicommutation in flow analysis. Part 1. Binary sampling concepts, instrumentation and spectrophoto-metric determination of iron in plant digests, Anal. Chim. Acta 293 (1994) 129. 

C.A. Tumang, G.C. Luca, R.N. Fernandes, B.F. Reis, F.J. Krug, Multicommutation in flow analysis exploiting a multizone trapping approach spectrophotometric determination of boron in plants, Anal. Chim. Acta 374 (1998) 53. 

Figure 1 Schematic illustration of flowing stream manifolds devised for the automatic determination of relevant environmental parameters in water samples using various flow techniques (A) flow injection analysis, (B) sequential injection analysis, (C) multicommutation flow injection analysis, (D) multisyringe flow injection analysis. The sequential injection-lab-on-valve configuration is depicted in previous article Flow injection analysis-detection techniques. S, sample R, reagent C, carrier D, detector IV, injection valve HC, holding coil RC, reaction coil MV, multiposition valve SV, solenoid valve SP, syringe pump MP, multisyringe pump PP, peristaltic pump St, stopper W, waste.

We may classify flow methods in nonresolutive (SFA, flow injection analysis (FIA), sequential injection analysis (SIA), multicommutated flow injection analysis (MCFIA), multipumping flow systems (MPFS), etc.) and resolutive ones (chromatographic techniques, capillary electrophoresis, etc.). In this book we will mainly focus on nonresolutive flow methods of analysis. 

In fact, multicommutated flow injection analysis systems use a digital I/O board to control fastswitching solenoid valves, and so did early MSFIA systems to control independent solenoid valves. 

Computer advances have played a major role in flow techniques development. On the one hand, one of the greatest hindrances to the development of flow techniques other than segmented flow analysis (SFA) and flow injection analysis (FIA) was the lack of interfaces to control the analytical equipment via a computer. Most flow techniques require computer control, but FIA which has the invaluable advantage of using very simple assemblies that are easy to control manually. This provided popularity and widespread success to this technique, immediately after its inception. By contrast, the need for computer control in SIA and other multicommutated flow techniques together with the lack of experience in connecting computers to instruments at the time it was developed delayed its success. 

Multicommutated Flow Injection Analysis, Multisyringe Flow Injection Analysis, and Multipumping Flow Systems... 

There is a clear linkage between the development of flow analysis and that of the commutation concept [33]. Evolution of the commutation concept has led to the proposal and development of different generations of flow analyzers. The main multicommutated flow techniques are described in following sections. 

Miranda, C. E. S., B. F. Reis, N. Baccan, A. P. Packer, and M. F. Gine. 2002. Automated flow analysis system based on multicommutation for Cd, Ni and Pb online pre-concentration in a cationic exchange resin with determination by inductively coupled plasma atomic emission spectrometry. Anal. Chim. Acta 453 301-310. 

Silva, M. F., I. V. Toth, and A. O. S. S. Rangel. 2006. Determination of mercury in fish by cold vapor atomic absorption spectrophotometry using a multicommutated flow injection analysis system. Anal. Sci. 22 861-864. 

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