Electrocatalytic and flow-injection determination of the antioxidant tert.-butylhydroxyanisole at a nickel phthalocyanine polymer modified electrode

The behaviour of a nickel phthalocyanine polymer-coated glassy carbon electrode has been investigated in order to test it as an amperometric detector in flow systems. The oxidation process of the antioxidant tert.-butylhydroxyanisole (BHA) has been studied for this purpose. The monomer Ni(II)-4,9,16,23-tetraaminophthalocyanine was synthesized and characterized. Electropolymerization was accomplished by repetitive cycling between −0.2 and + 0.9 V in a dimethyl sulfoxide solution of the monomer. The characteristics of the BHA oxidation process at the polymeric modified electrode were examined by linear sweep voltammetry. A flow-injection method with amperometric detection based on this oxidation process has been developed. At an applied potential of 0.70 V, calibration graphs were linear within the range 10-0.01 mg l−1 BHA with a limit of detection of 2.7 μg l−1 BHA (1.5 × 10−8 mol l−1). Interferences from BHT (tert.-butylhydroxytoluene), TBHQ (tert.-butylhydroquinone), propyl gallate, ascorbic acid, sodium bisulfite and citric acid were tested. The method was applied to the determination of BHA in biscuits samples.