¹H NMR Pure Shift Metabolomic Analysis of Black Tea

Pure shift NMR provides a significant improvement in resolution, by suppressing homonuclear scalar couplings, but at the cost of sensitivity. This work compares the untargeted metabolomic analysis results using different pure shift methods with those from conventional 1D ¹H and 2D J-resolved experiments. The comparison was made on a selected set of black teas from two cultivars. Multivariate analysis results indicate that despite the lower sensitivity, the enhanced resolution pure shift NMR experiment produces comparable discrimination of the different varieties of black tea to that obtained with conventional 1D ¹H NMR spectra. The combination of 2D J-resolved and PSYCHE (pure shift yielded by chirp excitation) spectra simplifies signal assignment, which is of importance in metabolomic studies.