PORTABLE AMPEROMETRIC SENSOR FOR MEASURING THE TOTAL ANTIOXIDANT ACTIVITY OF SUBSTANCES

Abstract

Understanding the role of antioxidants as substances interrupting free radical reactions intensifies the search for new natural and synthetic substances with antioxidant properties. Along with this, intensive research is underway to create methods for assessing the antioxidant (AO) properties of various substances and devices for determining antioxidant activity (AOA). This article proposes an amperometric method and a sensor for measuring the total antioxidant activity of substances. The method is based on the process of oxygen electroreduction in the absence and presence of antioxidants of various origins in the solution. The measurement of the analytical signal before and after the introduction of the antioxidant substance into the electrochemical cell is carried out using a portable two-electrode sensor, "pencil" type, with a silver cathode, on which a potential of -500 mV is applied from a DC source (batteries). As an antioxidant standard, a 1% solution of ascorbic acid in a phosphate buffer with a pH of 6.86 was conventionally adopted. The sensor is connected to the measuring and driving device through a microcircuit - an operational amplifier. The measured signal in arbitrary units is displayed on the liquid crystal screen of the setting and measuring device and characterizes the maximum depolarization current of the indicator electrode. Using the resistors of the measuring device, a range of 0 - 100 units is set, for the analyte in the absence of an antioxidant and in the presence of a standard - 1% ascorbic acid solution, conventionally taken as 100%, respectively. Thus, the antioxidant activity of substances can be measured as a percentage relative to ascorbic acid (or other antioxidant). The results of determining the total antioxidant activity of some drinks and aqueous-alcoholic extracts of medicinal plants are presented.