Coupling organic and biological reactions with electrochemical measurements for analytical purposes

Abstract

The potentialities for the determination of organic compounds of biological interest, which are inherent in coupling preliminary organic and biological reactions of nearly quantitative or highly reproducible yield with electrochemical measurements, are evident from consideration of the production of (a) electroactive species for polarographic measurement and (b) inorganic ions and gases for potentiometric measurement from organic compounds otherwise inert in terms of these approaches. Reactions, which are readily coupled with various polarographic techniques, include addition of an electroactive substituent, formation of an electroactive species or of electroactive complexes, and utilization of catalytically active species. In the case of potentiometry, advantage can be taken of the specificity of enzyme-catalyzed reactions, which (a) produce ammonium, cyanide and other ions, for which suitable ion-selective electrodes are available, or (b) produce or consume gases, for which selective gas-membrane electrodes are available; many of the reaction-electrode combinations so utilized can also be used for the determination of the enzyme involved. Use of potential mediators constitutes a special category for the production of potentiometric activity. Conductometry, coulometry and amperometry can also be used, following a preliminary chemical reaction, for monitoring gas chromatographic column effluents and solution compositions. In the case of all of these approaches, consumption of an electroresponsive reagent can be used to determine organic compounds by either differential concentration measurement or titration. © 1975.