Calibration flow-injection analysis systems

Nie et al. used a flow injection chemiluminescence method for the determination of dipyridamole in Persantin tablets [51]. A flow injection analysis system equipped with a chemiluminescence detector was used. Sodium hypochlorite was used as a chemiluminescent substance, and Triton X-100 was used as an enhancer of the chemiluminescence reaction. Sample solutions (pH 4-6) was injected into 0.2% Triton X-100 and treated with 0.5% sodium hypochlorite, and the chemiluminescence intensity then measured. The calibration graph was linear from 0.04 to 10 pg/mL of Persantin tablets (as its active ingredient dipyridamole), with a detection limit of 11 ng/mL. Recoveries were quantitative and the relative standard deviation ( = 3) was 2.7%. The method has been used to determine Persantin in injection and tablets, and the results obtained using this method agreed with those obtained by the Chinese Pharmacopoeial method. 

A flow injection analysis system (FIAS) for direct analysis of raw nrine was mentioned earlier (Lorber et al. 1997). No sample preparation was carried ont so the probability of cross contamination was negligible. The response profile of the ICPMS detector is typical of the FIAS sample introduction method, as shown for a calibration solution containing 100 ng L" uranium (top frame of Figure 4.11) and an actual raw urine sample containing 3.8 ng L (bottom frame). 

However, the best results were presented in a series of papers where the methylester tetramer was used as an element in an ISE array both in conventional dip-type measurements [14] and in a flow-injection analysis system [15,16]. Using sophisticated calibration and sensor modelling techniques, these papers rigorously demonstrated that the methylester tetramer (Table 1,2) could be applied to blood sodium analysis with excellent results (Figure 3). Furthermore, the same ISE was shown to be suitable for the analysis of sodium in mineral water samples. 

P.C. Thijssen, L.T.M. Prop, G. Kateman and H.C. Smit, A Kalman filter for calibration, evaluation of unknown samples and quality control in drifting systems. Part 4. Flow Injection Analysis. Anal. Chim. Acta, 174 (1985) 27-40. 

Sample preparation, injection, calibration, and data collection, must be automated for process analysis. Methods used for flow injection analysis (FLA) are also useful for reliable sampling for process LC systems.1 Dynamic dilution is a technique that is used extensively in FIA.13 In this technique, sample from a loop or slot of a valve is diluted as it is transferred to a HPLC injection valve for analysis. As the diluted sample plug passes through the HPLC valve it is switched and the sample is injected onto the HPLC column for separation. The sample transfer time typically is determined with a refractive index detector and valve switching, which can be controlled by an integrator or computer. The transfer time is very reproducible. Calibration is typically done by external standardization using normalization by response factor. Internal standardization has also been used. To detect upsets or for process optimization, absolute numbers are not always needed. An alternative to... 

Vinas et al. [46] also determined penicillamine by chemiluminescence - flow injection analysis. The sample was dissolved in water, and a portion of resulting solution was introduced into an FIA system consisting of 5 mM luminol in 0.1 M KOH-boric acid buffer (pH 10.4), 50 pM Cu(II), and 10 mM H202 eluted at 7.2 mL/min. Chemiluminescent detection was used, the calibration graphs were linear from 0.1 to 10 mM of penicillamine, and the coefficients of variation were from 1.2% and 2.1%i. 

Since ISEs can be used in continuous flow systems or in flow systems with sample injection (flow injection analysis, FIA)21 their application is wide, not limited to discrete samples. Analysis time becomes shorter, with faster recycling. Additionally, in flow systems the experimental assembly and data analysis can be controlled automatically by microcomputer, including periodic calibration. Another development is the use of sensors for the detection of eluents of chromatographic columns in high-pressure liquid chromatography (HPLC). Miniaturization has permitted an increase in the use of sensors in foods, biological tissues, and clinical analyses in general. 

A useful and rapid method of automated analysis is the technique of flow-injection analysis (FIA). The sample or a reagent is injected into the stream of a solution of constant composition. Calibration of FIA systems requires the injection of standard solutions, equal in volume to that of the sample, into the carrier stream. The backgrormd chemical composition of the standards should be equal, as nearly as possible, to that of the samples. Frequent standardization is not necessary because the measurement of peak height, albeit on a sloping base line, is relatively unaffected by cell voltage drift. Some difficulties can appear with peristaltic pumps, owing to extraneous potentials caused by pulsation of the stream. Cells with a small volume (<20 pi) or the cells of the wall-jet type are the most acceptable for continuous measurements. ... 

Evmiridis, N.P. Papamichael, E.M. (1991). Investigation of the error structure of the calibration curve for periodate determination by flow-injection analysis and chemiluminescence detection. Chemom. Intell. Lab. Systems,Vol. 12, p>p. 39-47 Fersht, A. (1999) Structure and Mechanism in Protein Science A Guide to Enzyme Catalysis and Protein Folding, (1st edition),W.H. Freeman, ISBN-10 0-7167-3268-8, New York] Fletcher, R. (1%5). Function minimization without evaluating derivatives - a review. Computer Journal, VoL.8, pp. 33 1... 

The flow injection analysis of iron (III) was validated by injecting known amounts of standards in the flow system. Calibration graphs were constructed on two... 

Fig. 2.4 Schcane of an ion-selective field effect transistm (ISFET)— flow injection analysis (FIA) system. The soil extract sample, calibration, and base solutions are sequentially introduced through a flow injection line system with multiple inlets, and are transported to a multi-ISFET chip with outputs that continuously change due to the passage of the sample through the flow cell...

Some biosensors were designed to follow the different stages of a production line one by one, by semi-condnuous measurement. In this case, the biosensor is used with a system of flow injection analysis (FIA). Small sample volumes are used, and the problems of contamination in the fermentation industry can be avoided. There are also applications in biomedical analysis laboratories, where faster methods reduce the cost of each analysis. Finally, the automadon of FIA is possible using a microcomputer for data collection and management of the various steps of biosensor calibration and measurement. 

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