MIL-101(Cr) /PANI composite doped by silica nanoparticles as an efficient sorbent for solid phase extraction of thymol and carvacrol in food samples followed by GC-FID measurement

A novel metal organic framework/polyaniline (MIL-101(Cr)/PANI) composite was synthesized1 and doped by SiO2 nanoparticles. The composite structure and morphology were characterized using FT-IR and SEM instruments. The prepared MIL-101(Cr)/PANI-Si composite was then packed inside a proper cartridge and evaluated for solid phase extraction (SPE) [2-4] of thymol and carvacro[l], as the most important antioxidants in food samples, followed by GC-FID determination. The influence of the important experimental variables on the efficiency of the proposed SPE-GC-FID method, including pH and volume of sample solution, type and volume of eluent, and ionic strength were studied and optimized. Under the optimal conditions, the relative standard deviations (RSDs) and the limits of detection (LODs) were found to be 3.8, 9.8% and 0.1, 1 ng mL-1, for thymol and carvacrol, respectively. The linear dynamic ranges (LDRs) for the calibration curves of both analytes were obtained over the range of 10-10000 ng mL-1.The prepared MIL-101(Cr)/PANI-Si sorbent was successfully applied for the analysis and recovery of thymol and carvacrol in Lamiaceae plant extracts and honey sample, with relative recoveries in the range of 90-122%.