Polarographic determinations, optimum

TABLE 3.6 Optimum Conditions for Polarographic Determination of Inorganic and Organic Substrates a ... 

A review of the methods which facilitates the rapid choice of an optimum procedure to be used for the determination of procaine and other medicinals derived from aminocarboxylic acids has have been published [28]. This review covers volumetric, optical, electrochemical and polarographic methods. 

Many variables are of importance in determining the course of an electrode reaction. In order to determine the optimum conditions for an electrosynthesis the use of current-voltage curves obtained at microelectrodes is of great value. A series of such curves are produced using different electrode materials, solvents, and pH when mercury is used as the electrode material, the ordinary polarographic technique8-10 is applied. With some experience it is possible from such a series of experiments to choose conditions suitable for the reaction. 

An introductory chapter on the furoquinoline alkaloids with excellent coverage and leading references to the literature has been published as part of a general volume on alkaloids.1 A detailed chromatographic analysis of quinoline alkaloids in liquid-liquid systems with buffered aqueous phase and a polarographic method for the determination of dubinidine from Haplophyllum foliosum have been reported.2 From a pH-R f relationship, the optimum conditions for extraction and chromatography were developed.20... 

Resolution and trace determination of inorganic oxyanions are important for assay purposes in commercial samples. The dc polarographic behaviour of these oxyanions and the resulting application have been described earlier. The detection limit of dc polarography is usually about 10 M but may be higher under non-optimum conditions. Since differential pulse polarography (dpp) and voltammetry should improve sensitivity at trace level concentrations, the use of dpp and voltammetry for determination of some oxyanions has been studied. In the present work applicability of dpp for quantitative trace determination and resolution of TeO " and VO in presence of some oxyhalide anions such as BrOj, lOj and 10 is investigated. 

The electrochemistry of hydrazides and their derivatives is of potential interest due to their biological importance as antituberculosis compounds. In this context the polarographic behaviour and reduction mechanism of various arylidene acid hydrazone has been studied in the past over a wide range of pH. The polarographic methods which has been applied previously for the determination of the hydrazide derivatives are insufficient for trace analysis. The detection limit for dc polarography is usually ca. 10 M but be higher under non-optimum conditions. 

These authors suggest that (a) the observed effect of reductants on mushroom polyphenol oxidase is dependent on whether a polarographic or spectroscopic method is used to assay the enzyme (b) the spectrophotometric method is useful to determine the optimum reductant concentration required to inhibit browning and (c) the polarographic method is useful to establish whether the inactivation of the enzyme is irreversible. 

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