Determination of the Synthetic Antioxidants Butylated Hydroxyanisole (BHA) and Butylated Hydroxytoluene (BHT) by Matrix Acidity-Induced Switchable Hydrophilicity Solvent-Based Homogeneous Liquid-Liquid Microextraction (MAI-SHS-HLLME) and High-Performance Liquid Chromatography with Ultraviolet Detection (HPLC-UV)

A rapid and easy sample pretreatment procedure, matrix acidity-induced switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction, has been developed for the isolation of the synthetic antioxidants butylated hydroxyanisole and butylated hydroxytoluene from vinegar samples. Di-(2-ethylhexyl)phosphoric acid (DEHPA) was selected as the extraction solvent and its hydrophilic form was obtained in alkaline solution followed by the addition of vinegar, which acted as both the sample and the inductor of the switching reaction leading to the formation of DEHPA microdroplets. There was no need to centrifuge at this step, since the DEHPA phase containing the analytes was collected from the resulting mixture through magnetic retrieval due to its high affinity for Fe3O4 nanoparticles. After being magnetically separated, the desorbed analytes were analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-UV). Under the optimized conditions, the limits of detection for the analytes were between 3.2 and 5.5 mu g L-1 and the linear dynamic range was from 10 to 500 mu g L-1. Good precision was obtained with relative standard deviations less than 7.8%. Recovery assays for spiked apple, grape, and white vinegar provided recoveries from 86 to 105%.

Automated summary

A rapid and easy sample pretreatment procedure was developed for the isolation of synthetic antioxidants from vinegar samples. The method, based on matrix acidity-induced switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction, showed good precision and recovery rates for spiked apple, grape, and white vinegar samples. The analytes were analyzed using high performance liquid chromatography with ultraviolet detection under optimized conditions, with limits of detection ranging from 3.2 to 5.5 μg L-1.