A Fast and Sensitive Method for the Analysis of 4-Methylimidazole in Tea Extract: Stir-Bar Sorptive Extraction Combined with GC-MS

Abstract

A novel and efficient analytical method was developed for the determination of 4-methylimidazole (4-MeI) in tea extracts using stir-bar sorptive extraction (SBSE) coupled with gas chromatography-mass spectrometry (GC-MS). Extraction parameters were optimized using ethylene glycol- and silicone-coated stir bars. The ethylene glycol-coated stir bar was used due to its higher extraction efficiency. The method demonstrated excellent linearity over the range of 2 mu g/mL and 100 mu g/mL (R2 = 0.9982), with a limit of detection (LOD) of 1.19 mu g/mL and a limit of quantification (LOQ) of 3.97 mu g/mL. Method precision was confirmed with intra- and inter-day relative standard deviations of less than 1.6% and recoveries exceeding 102.26 +/- 3.82%. The combined and expanded uncertainties were calculated as 0.0187 and 0.0373, respectively. Compared with liquid chromatography mass spectrometry (LC-MS/MS) and Quick, Easy, Cheap, Effective, Rugged and Safe-based (QuEChERS) methods, the developed SBSE-GC/MS protocol offers reduced matrix interference, simplified sample preparation, and comparable sensitivity. Real sample analyses validated the method's applicability for routine monitoring of 4-MeI in commercial tea-based products. This approach offers a fast, reliable, and eco-friendly alternative for monitoring food safety and detecting thermally generated contaminants.