Thermosensitive poly(N-isopropylacrylamide) hydrogel/highly internal phase emulsion porous polymer tube tip solid-phase extraction for the determination of methylimidazoles in beverage

Poly(N-isopropylacrylamide) thermosensitive hydrogel tube tip solid-phase extraction/ultra-high liquid chromatography-mass spectrometry (UPLC-MS/MS) method was developed for analysis of methylimidazoles in beverages. Thermosensitive poly(N-isopropylacrylamide) (PNIPA) hydrogel solid-phase extraction (SPE) medium was prepared on the surface of highly internal phase emulsion (HIPE) porous polymer by thermally initiated polymerization in a tube tip. The temperature sensitive SPE medium has the characteristics of high porosity and high specific surface area. When the temperature is higher than 30.0℃, it can well adsorb polar molecular, and could quickly desorb polar molecular when the temperature was less than 20.0℃. The tube tip SPE coupled with UPLC-MS/MS method was established for the determination of three polar molecules including 1-methylimidazole, 4-methylimidazole and 2-methylimidazole, with linear ranges of 2.50 - 240 μg/L, and detection limits of 1.20, 1.20 and 0.65 μg/L, respectively. The method was applied to the determination of three methylimidazoles in beverages with the spiked recoveries of 81.5%-115.5% and the RSD of 0.6%-5.0%, and the relative errors of the results with the national standard UPLC-MS/MS method were in the range of -8.5%-8.9%.