The Development of Flow Analysis

E.A.G. Zagatto, B.F. Reis, C.C. Oliveira, R.P. Sartini, M.A.Z. Arruda, Evolution of the commutation concept associated with the development of flow analysis, Anal. Chim. Acta 400 (1999) 249. 

A critical view of the development of flow analysis shows that efforts to improve mixing of the solutions have exploited flow regimes other than laminar flow. 

The introduction of SIA marked a new era in the development of flow analysis by addressing some important limitations associated with FIA. The advantages of SIA include ... 

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. 

The development of flow analysis methods for AA is important because of the presence and significance of this analyte in foodstuffs, pharmaceuticals, and biological fluids, with implications in redox processes, human health, and food quality. However, so far there are few flow analysis methods for simultaneously determining AA and DHAA, or simultaneously determining several vitamins, including vitamin C (the sum of the contents of AA plus DHAA). Furthermore, most flow analysis methods do not include online sample preparation, except for analytical separations and derivatization reactions, and only two online sample dilution methods allow the fully automatic determination of AA. 

The autoanalyzer represented a substantial advance in the ability to make repetitive on-board chemical measurements. The development of flow-injection analysis promises to enlarge enormously the scope and speed of such methods. The flow-injection methods were pioneered in clinical chemistry, and are being developed for oceanography by Kenneth S. Johnson and Robert L. Petty. Dana Kester and Richard W. Zuehlke are also developing new autoanalyzer techniques for the rapid analysis of certain trace metals in seawater. One of the most technologically exciting prospects for the future involves the use of fiber optics to transmit a spectroscopic signal from an in-situ sensor to the ship s deck. 

Commutation refers to the act of modifying the manifold status [69], e.g., substituting manifold components or changing the direction of a flowing stream by means of a commutator device, and its exploitation can enhance system versatility and hence system performance. There is a clear link between the developments in flow analysis and commutation [151]. 

In summary, the history of flow analysis is closely associated with the development and improvement of commuting devices. 

The development of flow systems has contributed to a decrease in the volume of samples and reagents needed for a particular chemical analysis. This tendency was reinforced with the advent of micro-scale analytical methods relying on, e.g., electrophoresis and micro-total analysis systems (pTAS), which influenced the introduction of miniaturised flow systems. Miniaturisation achieves a significant reduction in sample and reagent consumption and allows the design of compact and portable systems. As a result, the generation of chemical waste and the cost of analysis are reduced, and the possibility for in situ or in vivo assays is increased. Thus, in recent years, several miniaturised flow systems have been proposed. 

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. 

Automated gate location technology was developed to shorten the number of flow analysis trials. To help users to reach optimum gate location with manual controls of flow patterns. Simple flow simulator was developed. Since it takes less than a tenth of the time for flow analysis, the technologies can be practically useful. 

Capillary pressure gradients and Marongoni flow induce flow in porous media comprising glass beads or sand particles [40-42], Wetting and spreading processes are an important consideration in the development of inkjet inks and paper or transparency media [43] see the article by Marmur [44] for analysis of capillary penetration in this context. 

Computer modelling provides powerful and convenient tools for the quantitative analysis of fluid dynamics and heat transfer in non-Newtonian polymer flow systems. Therefore these techniques arc routmely used in the modern polymer industry to design and develop better and more efficient process equipment and operations. The main steps in the development of a computer model for a physical process, such as the flow and deformation of polymeric materials, can be summarized as ... 

Environmental Applications Although ion-selective electrodes find use in environmental analysis, their application is not as widespread as in clinical analysis. Standard methods have been developed for the analysis of CN , F , NH3, and in water and wastewater. Except for F , however, other analytical methods are considered superior. By incorporating the ion-selective electrode into a flow cell, the continuous monitoring of wastewater streams and other flow systems is possible. Such applications are limited, however, by the electrode s response to the analyte s activity, rather than its concentration. Considerable interest has been shown in the development of biosensors for the field screening and monitoring of environmental samples for a number of priority pollutants. 

Entrance andExit SpanXireas. The thermal design methods presented assume that the temperature of the sheUside fluid at the entrance end of aU tubes is uniform and the same as the inlet temperature, except for cross-flow heat exchangers. This phenomenon results from the one-dimensional analysis method used in the development of the design equations. In reaUty, the temperature of the sheUside fluid away from the bundle entrance is different from the inlet temperature because heat transfer takes place between the sheUside and tubeside fluids, as the sheUside fluid flows over the tubes to reach the region away from the bundle entrance in the entrance span of the tube bundle. A similar effect takes place in the exit span of the tube bundle (12). 

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