Flow injection analysis amperometric detector

Enzyme linked electrochemical techniques can be carried out in two basic manners. In the first approach the enzyme is immobilized at the electrode. A second approach is to use a hydrodynamic technique, such as flow injection analysis (FIAEC) or liquid chromatography (LCEC), with the enzyme reaction being either off-line or on-line in a reactor prior to the amperometric detector. Hydrodynamic techniques provide a convenient and efficient method for transporting and mixing the substrate and enzyme, subsequent transport of product to the electrode, and rapid sample turnaround. The kinetics of the enzyme system can also be readily studied using hydrodynamic techniques. Immobilizing the enzyme at the electrode provides a simple system which is amenable to in vivo analysis. 

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... 

Cosio et al. (2006) used an electronic tongue system based on flow injection analysis (FIA) with two amperometric detectors, together with the use of an electronic nose, in order to classify olive oil samples on the basis of their geographical origin. Counter-propagation maps were used as classification tools. 

In a potentiostatic step experiment on an ultramicrodisc electrode, the current attains a limiting value in a time of the order r ID. In addition to this time scale becoming shorter with decreasing r, the mass transport rate of species to the electrode increases. As a consequence, one motivation for the development of devices using UMEs has been the resulting insensitivity of the limiting current to fluctuations of solution flow rate [62]. Hence UMEs have found widespread use as electrochemical detectors in fluid flow experiments, such as amperometric liquid chromatography (e.g., Ref. [63]) and flow injection analysis (e.g., Ref. [64]). Incidentally, this implies that the current should also be insensitive to vibration. 

The highest sample frequency achieved up to now has been obtained in a computer-controlled flow injection analysis (FIA) system (Olsson et al., 1986b) using an amperometric flow-through cell (Bertermann et al., 1981). A Pt electrode of 0.5 mm diameter (VEB Metra Radebeul, GDR) has been used as hydrogen peroxide detector. GOD was immobilized in polyurethane (thickness, 0.02 mm, enzyme loading, 50 U/cm2) and... 

Potentiometric electrodes of all types In flow-injection analysis (FIA) glass, ion-selective, amperometric electrodes, etc., can all theoretically be used in a detector cell to quantify some chemical substance. 

J. Matysik, E. Soczewinski, E. Zminkowska-Halliop, and M. Przegalinski, Determination of o-Diphenols by Flow Injection Analysis with an Amperometric Detector. Chem. Anal. (Warzaw), 26 (1981) 463. 

H. Ma and H. Yan, Study on Application of Flow Injection Analysis (FIA) with an Amperometric Detector—Determination of Silver Ion in Waste-waters by FIA [in Chinese]. Huanjing Huaxue, 1 (1982) 422. 

H. Ma, L. Jin, and H. Yan, Flow Injection Analysis of Traces of Free Cyanide in Surface and Ground Waters with an Amperometric Flow-Through Detector [in Chinese]. Kexue Tongbao, 28 (1983) 1145. 

T. Yao, Flow Injection Analysis for Cholinesterase in Blood Serum by Use of a Choline-Sensitive Electrode as an Amperometric Detector. Anal. Chim. Acta, 153 (1983) 169. 

H. Huck, A. Schelter-Graf, and H. L. Schmidt, Measurement and Calculation of the Calibration Graphs for Flow Injection Analysis Using Enzyme Reactors with Immobilized Dehydrogenases and an Amperometric NADH Detector. Bioelectrochem. Bioenerg., 13 (1984) 199. 

H. Satake, Y. Kohri, and S. Ikeda, Flow Injection Analysis of Hydroqui-none, Pyrocatechol, Resorcinol and Pyrogallol with Amperometric Detector [in Japanese]. Nippon Kagaku Kaishi, 1 (1986) 43. 

D. Eadington and J. A. W. Dalziel, Reductive Determination of Metal Ions by Flow Injection Analysis Using Amperometric Amalgam Detectors. Anal. Proc., 23 (1986) 434. 

Various analytical methods now employ amperometric measurements as part of their procedures. In particular, amperometric titrations have been widely used for the analysis of various substances in samples ranging from water to radioactive materials. Also, amperometric sensors, such as the dissolved oxygen probe and various amperometric biosensors, are widely used for clinical, environmental, and industrial monitoring. Furthermore, amperometric detectors have gained considerable use since the 1970s in high-performance liquid chromatographic determination of various substances and in flow injection analysis. 

Amperometric Detectors for Chromatography and Flow Injection Analysis... 

A pentaerythritol-based dendrimer modified with bis-terpyridyl Ru(II) was shown to be effective as a catalyst for the electrochemical oxidation of methionine (L-Met) and cystine (L-Cys) in aqueous solution or the mixed solvent AN-water (12% AN) [100]. In this case, the dendrimer was mixed with carhon powder and, using a sol-gel hinder, the carhon electrode doped with the [Ru(tpy)2] " -functionalized dendrimer was prepared. The oxidation peak of [Ru(tpy)2] was enhanced by the addition of L-Met, indicating the electro-catalytic effect of the dendrimer. Using the composite electrode doped with the dendrimer as an amperometric detector for flow-injection analysis, a linear calibration curve was obtained over the range 1-lOpM of L-Met in phosphate buffer (pH 7.0). A similar cahbration curve was obtained for L-Cys over the range 1-10 pM in phosphate buffer (pH 2.3). 

A rotating enzyme-immobilized reactor and a flat pH electrode were incorporated into a sealed cell for use under continuous-flow/stopped-flow (SF) operation for the rapid determination of penicillins G and V in tablets and injectables [50]. A co-immobilization in a rotating bioreactor and amperometric detector resulted in a sensitive system for determination of succinylcholine and acetylcholine in pharmaceutical preparations [51]. A tandem system incorporating two rotating bioreactors into a continuous-flow/SF sample/reagentprocessing setup was apphed for the determination of alkaline phosphatase activity in serum samples [52]. By functional combination of the SF and flow-injection analysis (FIA), an automated micro apparatus was constructed resulting in significant reduction of the injection volumes of enzyme and substrate [53]. SF/continuous flow methods were apphed to acquire kinetic information also [54, 55]. 

Because of their stability against chemical dissolution and their effective promotion of oxidations of biochemical compounds, catalysts comprising inorganic polymers and other maCTomolecules that contain platinum-group metal centers will be the focus of the present report. The applications primarily will be as amperometric detectors in HPLC and in flow-injection analysis, in which case both surface-modified electrodes and doped CCEs are suitable. Specifically addressed will be the use of sol-gel processing as a means of immobilizing catalysts in composites. 

Ikeda, S., H. Satake, and Y. Kohri. 1984. Flow injection analysis with an amperometric detector utilizing the redox reaction of iodate ion. Chem. Lett. 6 873-876. 

Granger, M. C., J. Xu, J. W. Strojek, and G. M. Swain. 1999. Polycrystalline diamond electrodes Basic properties and applications as amperometric detectors in flow injection analysis and liquid chromatography. Anal. Ghim. Acta... 

Electrodes modified by eiectrodeposited 3-methylPT can be used as chemical sensors for organic and especially biological interesting molecules. The modified surfaces catalyze the oxidation of several compounds (e.g. ferrocyanide, catechol, ascorbic acid, hydroquinone, dopamine, epinephrine, acetaminophene, p-aminophenol, and reduced nicotinamide adenine dinucleotide). The sensitivity of these polymer-coated electrodes is 4 to 10 times higher than pure electrodes of platinum. Binary and also ternary mixtures can also be analyzed these electrodes are also suitable as an amperometric detector for flow injection analysis [211, 212]. 

An amperometric sensor for amino acids based on flow injection analysis (FIA) and using microelectrodes (10 pm diameter) primarily of P(Py) doped with sulfonate dopants such as tosylate and 3-sulfobenzoate was demonstrated by Akhtar et al. [823, 824]. Linear response was demonstrated for analytes such as aspartic acid and glutamic acid over the concentration range 7.5 X 10 to lO" with sensitivities in the region of 1.5 nC-M and detection limits of ca. 10 M. These authors also showed the use of a pattern recognition technique using the responses of six detector electrodes. Fig. 17-11 shows typical response of one of their sensors. 

Yao T. (1983) Flow injection analysis for cholinesterase in blood serum by use of a choline-sensitive electrode as an amperometric detector. Anal. Chim. Acta, 153, 169-174. 

This analysis is performed using a Dionex Model 12 ion chromatograph with 200pL sample loop, an eluent flow rate of 2.3ml min 1 (30% of full capacity) and a sample pump flow rate of 3.8ml min 1 (50% of full capacity). Pulse damper is installed just before the injection valve to reduce flow pulsation. A Dionex amperometric detector... 

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