Simultaneous kinetic determination of butylated hydroxyanisole and propyl gallate by coupling stopped-flow mixing technique and diode-array detection

Kinetic methodology was used for the first time to develop a simple, fast photometric method for the simultaneous determination of two food antioxidants, namely butylated hydroxyanisole (BHA) and propyl gallate (PG). The method is based on the different kinetic behaviour of these compounds when react with 3-methylbenzothiazolin-2-one hydrazone in the presence of cerium(IV) and on the joint use of the stopped-flow mixing technique and a diode-array detector, which allowed to obtain kinetic data at two wavelengths simultaneously. Calibration graphs were linear over the range 0.3–30 μg ml−1 for BHA and 1.6–27.5 μg ml−1 for PG. The relative standard deviation was 1.0–2.1%. Both antioxidants were determined simultaneously by using a system of two equations which was resolved by multiple linear regression. Mixtures of BHA and PG in ratios between 4 : 1 and 1 : 10 were satisfactorily resolved. The method was applied to the determination of these antioxidants in several food samples. Analytical recoveries ranged between 97.2 and 103.5%.