An electrochemical sensor for voltammetric determination of ascorbic acid using modified carbon paste electrode

Ascorbic acid awater soluble vitamin is an extremely important substance which plays a unique redox andelectrochemical role. It is known as an antioxidant[1]. It is one form of vitamin C.Eating foods rich in vitamin C is important for your overall health, especially if you are at risk for high blood pressure, common cold, Alzheimer’s disease, mental illness, cancer, infertility andcancer [2]. Due to its importance, many analytical techniques have been developed and reported for thedetermination of ascorbic acid inpharmaceutical preparations, biological fluids, food and beverages. The methods are: chromatography,spectrophotometry,mass spectrometry,flow injection,chemiluminescence andelectrochemical methods[3]. Among them electrochemicalapproaches are used extensively for the especial and sensitive properties because other methods usually need samplepretreatment that is time-consuming and grinding. It is generally believed that direct redox reactionof this specie at bare electrodes such as carbon or those metallicones,Hg, Au, Pt require a high overpotential. Thus, there have been numerous attemptsto enhance theelectrode kinetics using various CMEs [4]. In recent years, chemically modified carbon paste electrodes have received increasing attention due to their potential applications in variousanalyses and also due to their low background current (compared to solid graphite or noble metalelectrodes), high sensitivity, facility to prepare, low cost, stable response, large potential window and simple surface renewalprocess [5]. Since the discovery of carbon nanotubes (CNTs), great investigations were centralized on the studies of theirproperties and applications.Because CNTs possess several unique properties such as small size, high electricaland thermal conductivity, high chemical stability, high mechanicalstrength and high specific surface.Moreover, the subtle electronicbehavior of CNTsreveals that they have the ability to promoteelectron-transfer reaction and have a high electrocatalytic effectwhen used as electrode materials. All these fascinatingproperties make CNTs as a suitable candidate for the modificationof electrodes [6].In the present work, 2-Chlorobenzoyl ferrocene (2CBF) was synthesized and used to construct a modified carbon nanotube paste electrode. The electro-oxidation of ascorbic acid at the surface of the modified electrode was studied using cyclic voltammetry (CV), chronoamperometry(CHA), and square wave voltammetry (SWV). Under the optimized conditions, the square wave voltammetric peak currents of ascorbic acid increased linearly with ascorbic acid concentrations in the ranges of 1.0×10-7 to 7.0×10−5 M and detection limit of 64.0 nM was obtained for ascorbic acid. Finally this modified electrode was used for determination of ascorbic acid in real samples

Keywords:

Ascorbic acid , Carbone nanotube , Electrocatalytic , Carbon paste electrode , Modifier