Determination of phenolic antioxidants by HPLC with amperometric detection at a nickel phthalocyanine polymer modified electrode.

Abstract

The suitability of nickel phthalocyanine polymer-coated glassy carbon electrodes for the amperometric detection of the phenolic antioxidants 1er1-butylhydroxytoluene (BHT), lert-butylhydroxyanisole (BHA), propyl gallate (PG) and /ert-butylhydroquinone (TBHQ). after their separation by HPLC under gradient elution conditions, is demonstrated. An applied potential of +0.70 V (vs. Ag/ AgC!) was used, which offers the best signal-to-noise ratio and is considerably lower than those reported in the literature with conventional electrodes. A good separation of the four antioxidants was obtained in 17 min. Furthermore. no fouling of the electrode surface was observed when using the polymer modified electrode during the whole working day. Using TBHQ ii!, internal standard, detection limits of 5.5 ng, 7.5 ng and 30 ng (for a 50-µL volwne injected) were obtained for BHA, PG and BHT, respectively. As an application, the determination of the antioxidants contained in commercial chewing gum samples was carried out by applying a simple extraction procedure. It was demonstrated that only BHT was present as antioxidant in the, samples, in a concentration of 51 ± 3 µg g- 1• Sample linearity and recovery studies, after adding a known amount of BHT to the analyzed samples, confirmed the sutability of the proposed method.