Development of Colorimetric Detection of 2,4,5-Trimethyloxazole in Volatile Organic Compounds Based on Porphyrin Complexes for Vinegar Storage Time Discrimination

Abstract

2,4,5-Trimethyloxazole, an important volatile organic compound, is widely detected in food products such as wine and vinegar. The current study presents a colorimetric sensor array (CSA) made of porphyrins and pH indicator for analysing the 2,4,5-trimethyloxazole in complex volatile organic compounds (VOCs). Based on density functional theory (DFT), time-dependent density functional theory (TDDFT) and UV spectral analysis, porphyrin complexes were synthesized and optimized specifically for the discriminating of 2,4,5-trimethyloxazole. We explored the possibility of porphyrins binding with VOCs, and the binding energies, dipole moments or equilibrium constants of optimized porphyrins have an upward trend after combining with 2,4,5-trimethyloxazole. The colorimetric dye of 5,10,15,20-tetrakis(4-fluorophenyl)-21H,23H-porphine zinc (TPP-Zn-F) is found specifically sensitive to the compound of 2, 4, 5-trimethyloxazole. The optimized porphyrin can resist the interference of complex VOCs, and the accuracy of characterization of 2,4,5-trimethyloxazole was improved. Finally, CSA composed of TPP-Zn-F and two chemoselective dyes shows a great ability to identify the storage time of vinegar, and the rates of LDA and KNN algorithms to predict vinegar samples are 92.5% and 100%, respectively.