Flow injection analysis advantages

There are many potential advantages to kinetic methods of analysis, perhaps the most important of which is the ability to use chemical reactions that are slow to reach equilibrium. In this chapter we examine three techniques that rely on measurements made while the analytical system is under kinetic rather than thermodynamic control chemical kinetic techniques, in which the rate of a chemical reaction is measured radiochemical techniques, in which a radioactive element s rate of nuclear decay is measured and flow injection analysis, in which the analyte is injected into a continuously flowing carrier stream, where its mixing and reaction with reagents in the stream are controlled by the kinetic processes of convection and diffusion. 

Flow injection analysis—mass and tandem mass spectrometry in the analysis of surfactants—advantages and disadvantages 123 Horst Fr. Schroder... 

SPECTROMETRY—II. FLOW INJECTION ANALYSIS—MASS AND TANDEM MASS SPECTROMETRY IN THE ANALYSIS OF SURFACTANTS—ADVANTAGES AND DISADVANTAGES... 

The qualitative determination of anionic surfactants in environmental samples such as water extracts by flow injection analysis coupled with MS (FIA-MS) applying a screening approach in the negative ionisation mode sometimes may be very effective. Using atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI), coupled with FIA or LC in combination with MS, anionic surfactants are either predominantly or sometimes exclusively ionised in the negative mode. Therefore, overview spectra obtained by FIA—MS(—) often are very clear and free from disturbing matrix components that are ionisable only in the positive mode. However, the advantage of clear... 

Because of its advantages (high sensitivity and selectivity, low cost and miniaturization) amperometric detection has been frequently used in flow injection analysis (FIA) and RP-HPLC. However, it has been established that the peak area (detector response) considerably depends on the flow rate. A general approach has been proposed to predict the effect of flow rate on the peak area in FIA and RP-HPLC. The general form of the correlation describing the flow in a parallel plate cell with short rectangular electrodes is... 

Flow injection analysis is based on the injection of a liquid sample into a continuously flowing liquid carrier stream, where it is usually made to react to give reaction products that may be detected. FIA offers the possibility in an on-line manifold of sample handling including separation, preconcentration, masking and color reaction, and even microwave dissolution, all of which can be readily automated. The most common advantages of FIA include reduced manpower cost of laboratory operations, increased sample throughput, improved precision of results, reduced sample volumes, and the elimination of many interferences. Fully automated flow injection analysers are based on spectrophotometric detection but are readily adapted as sample preparation units for atomic spectrometric techniques. Flow injection as a sample introduction technique has been discussed previously, whereas here its full potential is briefly surveyed. In addition to a few books on FIA [168,169], several critical reviews of FIA methods for FAAS, GF AAS, and ICP-AES methods have been published [170,171]. 

Continuous analytical methods (amperometric and UV-absorption methods) are advantageous. However, sometimes only discontinuous methods (titrimetric and some photometric methods) are available due to expense. In such cases it is important to measure immediately after sampling to avoid the decay of ozone and in the case of liquid ozone to avoid degassing. Discontinuous photometric methods requiring the addition of chemicals to the sample can be converted to a continuous method by combination with flow injection analysis (FIA). This analytical technique requires instrumentation and is not easy to handle. 

Another recent development is the advent of pulse amperometry in which the potential is repeatedly pulsed between two (or more) values. The current at each potential or the difference between these two currents ( differential pulse amperometry ) can be used to advantage for a number of applications. Similar advantages can result from the simultaneous monitoring of two (or more) electrodes poised at different potentials. In the remainder of this chapter it will be shown how the basic concepts of amperometry can be applied to various liquid chromatography detectors. There is not one universal electrochemical detector for liquid chromatography, but, rather, a family of different devices that have advantages for particular applications. Electrochemical detection has also been employed with flow injection analysis (where there is no chromatographic separation), in capillary electrophoresis, and in continuous-flow sensors. 

The first prototype of a technologically improved IWAO was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a commercial cadmium ionophore [39]. Its incorporation in an IWAO allows a highly sensitive and portable optical system to be obtained for an situ chemical analysis as well. The authors propose a flow injection analysis (FIA) system for the determination of cadmium in water samples using a cadmium-selective IWAO, as an alternative method to the ones generally used in analytical control laboratories. It permits enhanced sensitive signals in short response times by taking advantage of the very thin membranes deposited over the circuit. 

Flow-injection analysis is a versatile technique to evaluate the performance of a detector system. CHEMFETs may have an advantage over ISEs because of their small size and fast response times. We have tested our K+-sensitive CHEMFETs in a wall-jet cell with a platinum (pseudo-)reference electrode. One CHEMFET was contineously exposed to 0.1 M NaCl and the other to a carrier stream of 0.1 M NaCl in which various KC1 concentrations in 0.1 M NaCl were injected. The linear response of 56 mV per decade was observed for concentrations of KC1 above 5 x 10"5 M (Figure 9). When we used this FIA cell (Figure 10) for determination of K+ activities in human serum and urine samples, excellent correlations between our results and activities determined by flame photometry were obtained (Figure 11). 

One of the most basic characteristics of a compound is its molecular mass in this context, much of today s popularity of MS can be traced back to the simplicity of molecular mass readout from API spectra. A common experiment is flow injection analysis (FIA). Here, an autosampler is used to inject an aliquot of dissolved sample into a liquid stream, which is provided by an LC pump, to the MS-detector. FIA offers the advantages of easy automation and fast cycle times of about 30 s per sample. In order to increase throughput, multiprobe autosam-... 

To alleviate these drawbacks, alternative methodologies relying on the continuous provision of fresh extractant volumes to the solid sample under mvestigation have been developed, characterized, and contrasted with the classical end-over-end extraction procedures. The fundamental principles of these novel, dynamic (nonequilibrium) strategies, based primarily on the use of continuous-flow analysis (Ruzicka and Hansen, 1988), flow injection analysis (Ruzicka and Hansen, 1988 Trojanowicz, 2000 Miro and Frenzel, 2004b), or sequential injection analysis (Ruzicka and Marshall, 1990 Lenehan et al., 2002), are described in detail below, and their advantageous features and limitations for fractionation explorations are discussed critically. 

The system combines the advantageous characteristics of flow injection analysis, such as a high sample throughput and low detection limits, with those of sequential injection analysis such as robustness and versatility. It was initially exploited for industrial process control, with spectrophotometric detection, for the determination of highly acidic or alkaline protolytes using an ingenious titration procedure [109], free... 

This architecture (Fig. 8.11) was dominant during the nineteen seventies and eighties, and was also exploited when LLE was implemented in flow injection analysis. Nowadays, it is still widely used, as emphasised in recent comprehensive reviews [153,161]. Further innovations involving the use of a supported liquid membrane between two aqueous phases [162] and /or taking advantage of the high versatility of the unsegmented flow systems have also been proposed. 

Flow-injection analysis, as stated earlier in this chapter, offers a host of substantial advantages over conventional analytical methodologies, namely automation capability, flexibility, low reactant consumption, great versatility, etc. Thanks to its automation capability, the FIA technique is a major alternative to many continuous flow methods in areas such as clinical chemistry which require the processing of a large number of samples in a time as short as possible. 

Flow-injection analysis (FIA) has gained tremendous importance for bioprocess control during the last few years [23-27], Although this is not an in situ or a real on-line analytical technique, it can be automated and operated at very high analysis cycle frequencies (quasi online). One of the most important advantages of FIA is the use of very small sample volumes. 

Shan et al. (1994) used alkaline phosphatase from Escherichia coli in immobilized enzyme reactors in a flow injection analysis system to perform rapid on-line enzymatic hydrolysis of organic phosphorus and detection of the released phosphate as molybdate-reactive phosphorus. This approach has several advantages compared with the conventional batch reaction approach ... 

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