Analyses of synthetic antioxidants by capillary electrochromatography using poly(styrene–divinylbenzene–lauryl methacrylate) monolith

Abstract

In this study, several organic polymer-based monoliths prepared by single step in situ copolymerization of styrene- and methacrylate ester-based monomers (styrene (S), divinylbenzene (DVB) and lauryl methacrylate (LMA)) were developed as stationary phases of capillary electrochromatography (CEC) for the analyses of synthetic antioxidants. These monoliths were characterized by examining the SEM image, IR spectrum, and measuring the pore size, surface area, conversion yield, and thermal decomposition temperature. The polymerization procedure was optimized by varying the reaction temperature, the reaction time, and the LMA–styrene ratio. The LMA–styrene ratio had the most significant influence on the peak symmetry of butylated hydroxyanisole (BHA) and 2, 6-di- tert-butyl-4-methyl phenol (BHT), the latter being greatly affected by excessive peak tailing in the poly(S–DVB) monolith. It showed that the interaction between the poly(S–DVB) monolith and the antioxidant (BHT or BHA) was significantly altered by the insertion of LMA. Compared with the best HPLC and CE methods previously reported, this proposed CEC method provides a comparable separation ability for the five antioxidants analyzed. This study demonstrates that the potentiality of poly(S–DVB–LMA) monolith as stationary phase, especially for CEC system, because of high thermal stability and good column reproducibility.