VOLTAMMETRIC DETECTION OF THIOCTIC ACID USING INORGANIC-ORGANIC COMPOSITE MATERIAL

Abstract:

Electrochemical detection of antioxidants using low-cost, simple, and reliable analytical devices is gaining a huge interest nowadays. Amongst the traditional analytical methods employed in the antioxidants quantification, the chromatographic and spectrochemical methods provide high sensitivity, selectivity, and accuracy. The need for rapid and simple detection methodologies including in vivo monitoring emerged in recent years thanks to the development of portable electroanalytical devices. In this work, we have developed a sensing platform containing a hybrid material composed of an inorganic redox mediator, namely Prussian Blue (PB), and an organic polymer like poly(3,4-ethylenedioxythiophene), for thioctic acid detection. The hybrid material is prepared onto glassy carbon electrodes using alternate current protocol. This protocol consists in the application of an excitation sinusoidal current having defined frequency and amplitude over a dc constant current. The hybrid sensing material has been electrochemically synthesized in two steps: firstly, the organic polymer is prepared in the presence of ferricyanide ions. In the second step, the ferricyanide-doped polymer layer is subjected to the in situ electrochemical reduction of Fe(III) via the alternate current protocol. This approach ensured the in-situ formation of the PB inorganic redox mediator within the organic matrix. The sensing platform was characterized by cyclic voltammetry and electrochemical impedance spectroscopy revealing the electrochemical activity of the PB component in aqueous solutions containing potassium ions. The as developed sensing platform was tested for the determination of thioctic acid in real samples. The response was linear on the concentration range from 50 to 500 μM, and with a detection limit of 7.5 μM, respectively. The accuracy of the sensing platform was proved by measuring broccoli ethanolic extract enriched with known amounts of thioctic acid. The obtained recovery values were in the range 99.38 % – 103%, confirming the good accuracy of the electroanalytical sensing platform.