DETERMINATION OF TERT-BUTYLHYDROXYANISOLE AND TERT-BUTYLHYDROXYTOLUENE BY FLOW-INJECTION WITH AMPEROMETRIC DETECTION

Two flow-injection methods are described for the determination of the antioxidants tert-butylhydroxyanisole (BHA) and tert-butylhydroxytoluene (BHT) based on their oxidation at a glassy carbon electrode. In both instances, the analytical solution is injected into a carrier stream consisting of a solution of perchloric acid and 5% (v/v) methanol. Calibration graphs are linear in the concentration ranges 1.0-10.0, 0.1-1.0 and 0.01-0.1 mg l-1 for BHA and 1.0-8.0, 0.1-1.0 and 0.02-0.1 mg l-1 for BHT. Detection limits for BHA and BHT are 2.5 and 6.0-mu-g l-1, respectively. The determination of BHA in the presence of BHT is possible because the former is more easily oxidized than the latter. Other compounds usually present in commercial antioxidant mixtures, such as citric acid or propylene glycol, do not interfere, although propyl gallate does. Good results were obtained by applying the proposed flow-injection methods to determine BHA in spiked corn oil and BHT in stabilized diethyl ether samples after extraction of the analytes.