ASCORBIC ACID DETERMINATION IN FRESH AND COMMERCIAL FRUIT JUICES BY DIFFERENTIAL STRIPPING VOLTAMMETRIC TECHNIQUE AT A GLASSY CARBON ELECTRODE

Abstract

Ascorbic acid, also known as Vitamin C cannot be synthesized by humans. Ascorbic acid is commonly found in a variety of vegetables and fruits such as mangoes, oranges, broccolis and lettuce. Hence, vegetables and fruits become the main sources of ascorbic acid to meet dietary intake. The differential pulse anodic stripping voltammetry (DPASV) technique using glassy carbon electrode (GCE) as a working electrode and phosphate buffer at pH 4.2 as a supporting electrolyte has been proposed for ascorbic acid determination in natural and commercial fruit juices. The optimum instrumental conditions for electroanalytical determination of ascorbic acid by the proposed DPASV technique were initial potential (Ei) = 0 V, end potential (Ef)= 0.8 V, accumulation time (tacc) = 60 s, scan rate (v) = 0.125 V/s and pulse amplitude = 0.150 V. The anodic peak appeared at 0.3598 V. The curve was linear from 0.028 to 1.703 mM (R2=0.9999) with a detection limit of 0.0114 mM. The precisions in terms of relative standard deviation (RSD) were 1.30%, 0.50% and 0.06%, respectively. The ruggedness of the proposed DPASV technique was tested with statistical F-test. Satisfactory recoveries ranging from 73.65±1.70% to 101.93±1.65% were obtained for three different known concentrations of AA in the fruit juice samples. It can be concluded that the proposed technique is precise, accurate, rugged, low cost, fast and has the potential to be an alternative method for routine analysis of ascorbic acid in natural and commercial fruit juices.