Carbon-nanotube-modified screen-printed electrodes, a cationic surfactant, and a peak deconvolution procedure: alternatives to provide satisfactory simultaneous determination of three synthetic antioxidants in complex samples

The development of electroanalytical methods for determining three or more analytes simultaneously in a complex sample is highly desirable. Unfortunately, this is not an easy task in electrochemical studies of organic compounds, and alternative methods to achieve this goal have been increasingly sought in recent years. To this end, the present investigation employed a combination of screen-printed electrodes (SPEs), cetyltrimethylammonium bromide (CTAB), and a peak deconvolution procedure as an alternative approach to improve the sensitivity and selectivity in the simultaneous determination of three antioxidants in samples of biodiesel and cosmetic oils. The use of CTAB also prevents the occurrence of SPE fouling by matrix constituents, being essential in the simultaneous detection of the antioxidants tert-butylhydroquinone (TBHQ), propyl gallate (PG), and butylhydroxyanisole (BHA). Under optimized conditions, the limit of detection proved satisfactory, with relative standard deviations of 0.99% for TBHQ, 2.1% for PG, and 0.61% for BHA, indicating that the method has satisfactory repeatability. The approach was successfully applied to determine the target antioxidants in biodiesel samples at different concentrations after simple, rapid dilution, yielding recovery rates of 98-106% for TBHQ, 98-103% for PG, and 92-101% for BHA. In the analysis of cosmetic oils, a deconvolution procedure was applied to achieve separation of the oxidation peak potentials, with recovery rates of 94% for PG and 101% for BHA using the standard addition method. The results were satisfactory compared with those obtained using high-performance liquid chromatography.