Flow injection analysis with an enzyme reactor bed for determination of ascorbic acid in brain tissue

Abstract

The utility of immobilized enzymes is now well established (1). Immobilized enzyme reactors (IMERs) have been used in conjunction with flowing stream analyses (2-5). In most of these applications the detector monitors an enzymatic reaction product(s) or some coreactant. However, one can em-

Immobilized enzymes in flow‐injection analysis: present and trends

“…Only once has IrO2 activated with cyanuric chloride been used as support [38]. Among organic supports, the commonest is nylon [14, 15 and 39-43], followed by a series of polymers and gels of different characteristics, such as propylene [44], sepharose [44][45][46][47][48], silica gel [13 and 49-52], octylagarose gel [46], wakogel C-100 [50], polyamide gel [53], aminocellulofine [54], glycophase [30] etc. (c, o).…”

“…[38] enzymes, as well as for the direct determination of co-enzymes in biological fluids (NAD + [17], ATP [77], NADPH and FMNH2 [47]. Little attention has so far been paid to the analysis for vitamins [45] and inorganic species such as Zn(II) [26], sulphite [72], pyrophosphate [48] or hydrogen peroxide [21, 25 and 79].…”

“…(4) By using differential measurements, i.e. by taking the difference between the signal provided by the sample in the presence and absence of analyte [45] or of the enzymatic reaction [60 and 82], achieved by sequential injection of two aliquots of sample [45 and 60], by splitting the injected sample [82] or by simultaneous injection of two sample plugs as the analytical signal. The use of two injection valves [84 and 85] coupled with the enzymatic reactor in the loop of the secondary valve is a recent alternative to these differential measurements [86].…”

Flow injection Fluorimetric Determination of Ascorbic Acid Based on its Photooxidation by Thionine Blue

“…Since the introduction of FI analysis, many flow systems have been developed for the determination of AA using several detection techniques, e.g., amperometric, 27 coulometric, 28 voltammetric, 29 potentiometric, 30 spectrophotometric [31][32][33][34] and spectrofluorimetric. 35 An alternative for FI determination of AA in complex matrices is to use an enzyme column of ascorbate oxidase to catalyse its oxidation to DHAA; 36,37 two measurements are made for each determination, one using the enzyme column and the other a blank column. The decrease in the signal compared with the blank is related to the amount of AA present.…”

Determination of vitamin C by flow injection analysis

“…The second contribution was an amperometric method using immobilised enzyme (ascorbic acid oxidase) reactors that allowed the determination of the vitamin in brain tissue, with good results. 13 In order to develop a photometric -FIA method for the determination of vitamin C we used the reagent chloramine T in the presence of starchpotassium iodide solution or methyl redpotassium bromide solution as an indicator,'4 by normal FIA in the first instance and by an FIA titration without a gradient chamber (expansion-scale technique)l5-18 in the second. Both methods are compared with each other and with the conventional titration procedures.…”