Voltammetric determination of para-aminobenzoic acid using carbon paste electrode modified with macrocyclic compounds

The voltammetric behavior of para-aminobenzoic acid (PABA) was studied at a carbon paste electrode and the electrodes modified with six-member macrocyclic compounds. The electrodes so formed were able to bind para-aminobenzoic acid ions chemically and gave better voltammetric responses than the unmodified ones. The macrocycles used as modifiers for the electrode preparation were 18-crown-6, dibenzo-18-crown-6 and 1,4,7,10,13,16-hexathiacyclooctadecane. Among these three six-membered macrocyclic modified electrodes, dibenzo-18-crown-6 showed more affinity towards PABA and a 1.5-fold increase in voltammetric signal was obtained. This increase in anodic peak current was then used for finding the linear working range, which was 0.4-500 mu g cm(-3) with a detection limit of 0.1 mu g cm(-3) by differential pulse voltammetry. Interference from other vitamins like thiamine hydrochloride (B-1), riboflavin (B-2), nicotinamide (B-3) pyridoxine hydrochloride (B-6) and ascorbic acid (Vitamin C) was also studied. The modified electrode could be used for the simultaneous determination of riboflavin, ascorbic acid and PABA. It has also been utilized for the analysis of PABA in pharmaceutical, dry yeast and cultural extract of spirulina samples. (c) 2006 Elsevier B.V. All rights reserved.