CATALYTIC-VOLTAMMETRIC DETERMINATION OF THE ANTIOXIDANT TERT-BUTYLHYDROXYANISOLE (BHA) AT A NICKEL PHTHALOCYANINE MODIFIED CARBON-PASTE ELECTRODE

The voltammetric behaviour of the antioxidant tert-butylhydroxyanisole (BHA), at a carbon paste electrode modified with the electron mediato r nickel phthalocyanine, is described, and a method for the determinat ion of this antioxidant, based on its oxidation on the modified electr ode, is proposed. Cyclic voltammograms showed a well-defined oxidation peak for BHA slightly shifted towards less positive potentials with r espect to that obtained at the plain carbon paste electrode. The peak current measured at the modified electrode is considerably higher than that obtained at the unmodified electrode. A modifier percentage of 2 %, a methanol percentage of 2% and a 0.1 mol/l HClO4 medium were chose n as working conditions. The i(p) vs upsilon1/2 plot obtained by linea r sweep voltammetry showed a linear relationship over the whole scan r ate range studied (5-2000 mV/sec) which is typical of a diffusion-cont rolled current. Using differential pulse voltammetry at DELTAE = 50 mV , linear calibration graphs were obtained in the concentration ranges 1.0-30.0, 0.10-1.0 and 0.02-0.10 mg/l BHA. The detection limit was 0.0 036 mg/l (2.0 x 10(-8) mol/l). Interferences from other substances com monly present in commercial antioxidant mixtures were tested. The deve loped method was applied to the determination of BHA in spiked potato flakes.