Catechol, electrochemical analysis

Because LCEC had its initial impact in neurochemical analysis, it is not, surprising that many of the early enzyme-linked electrochemical methods are of neurologically important enzymes. Many of the enzymes involved in catecholamine metabolism have been determined by electrochemical means. Phenylalanine hydroxylase activity has been determined by el trochemicaUy monitoring the conversion of tetrahydro-biopterin to dihydrobiopterin Another monooxygenase, tyrosine hydroxylase, has been determined by detecting the DOPA produced by the enzymatic reaction Formation of DOPA has also been monitored electrochemically to determine the activity of L-aromatic amino acid decarboxylase Other enzymes involved in catecholamine metabolism which have been determined electrochemically include dopamine-p-hydroxylase phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase . Electrochemical detection of DOPA has also been used to determine the activity of y-glutamyltranspeptidase The cytochrome P-450 enzyme system has been studied by observing the conversion of benzene to phenol and subsequently to hydroquinone and catechol... 

Krebs and co-workers synthesized a series of dinuclear copper(II) complexes as models for catechol oxidase 91 (365) (distorted SP Cu-Cu 2.902 A), (366) (distorted five-coordinate geometry Cu-Cu 3.002A), (367) (distorted SP Cu-Cu 2.995 A), (368) (distorted five-coordinate geometry Cu-Cu 2.938 A), and (369) (distorted SP Cu-Cu 2.874 A). These complexes were characterized by spectroscopic and electrochemical methods. From kinetic analysis, a catalytic order for catecholase activity (aerial oxidation of 3,5 -di - ter t-buty lcatec h o 1) was obtained.326... 

The electrochemical detector is extremely sensitive, but suffers from two main drawbacks. Firstly, the mobile ( ase has to be extremely pure, in particular, free of oxygen and metal ions. Secondly, by-products of the oxidation or reduction processes are often absorbed on the surface of the electrodes and thus, if quantitative activity is required, frequent calibration is necessary. Ultimately the electrodes have to be cleaned usually by mechanical abrasion and replaced in the cell. Electrochemical detection is particularly suitable for small bore columns and possibly, in the future, LC capillary columns, due to the fact that the detector can be made extremely small in size. The detector has had a fairly wide area of application. It has been used under oxidizing conditions for the detection of phenols, hydroquinone and catechols and in particular for many compounds of biological interest including, catecholamines (35). It has been used to determine substances of industrial interest, and agricultural chemicals (36). In its oxidation form, it has been used to detect amines of various types together with i enols and thiols. It has also been used in the analysis of ascorbic acid in food and biological materials, and in the pharmaceutical industry, for the analysis of multivitamin products. 

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