Determination of phenolic antioxidants by HPLC with amperometric detectionat a nickel phthalocyanine polymer modified electrode

The suitability of nickel phthalocyanine polymer-coated glassy carbon elect rodes for the amperometric detection of the phenolic antioxidants tert-buty lhydroxytoluene (BHT), tert-butylhydroxyanisole (BHA), propyl gallate (PG) and tert-butylhydroquinone (TBHQ), after their separation by HPLC under gra dient elution conditions, is demonstrated. An applied potential of +0.70 V (vs. Ag/AgCl) 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 m in. Furthermore, no fouling of the electrode surface was observed when usin g the polymer modified electrode during the whole working day. Using TBHQ a s internal standard, detection limits of 5.5 ng, 7.5 ng and 30 ng (for a 50 -mu L volume injected) were obtained for BHA, PG and BHT, respectively. As an application, the determination of the antioxidants contained in commerci al chewing gum samples was carried out by applying a simple extraction proc edure. It was demonstrated that only BHT was present as antioxidant in the samples, in a concentration of 51 +/- 3 mu g g(-1). Sample linearity and re covery studies, after adding a known amount of BHT to the analyzed samples, confirmed the sutability of the proposed method.