Solvent selection in the quality analysis of white tea by nuclear magnetic resonance spectroscopy

The study aimed to assess the influence of diverse solvent schemes on the qualitative analysis of white tea and to establish a more comprehensive quality evaluation. A systematic study of solvent optimization was carried out using the quality analysis of white tea as an exemplar, highlighting the critical role of selecting appropriate solvents in NMR-based sample preparation process. Six sample dissolution protocols, encompassing extraction and reconstitution solvents, were evaluated. The aqueous methanol solution proved effective as an extraction solvent, offering optimal metabolite coverage and spectral resolution. For reconstitution solvents, D2O facilitated identification of specific metabolites, such as amino acids, organic acids and carbohydrates, while DMSO-d6 exhibited better performance in detecting catechins, alkaloids and lipid resonances. Additionally, DMSO-d6 enabled better discrimination among various white tea varieties, whereas D2O system demonstrated better ability for estimating the storage duration of white tea. The characteristic metabolites were exactly those that each of the two solvents is suited to solubilize. Therefore, it can be concluded that solvents suitable for the detection of a class of metabolites are more likely to highlight differences in that type of metabolites and multi- solvent combination captures more comprehensive information, revealing the necessity of optimizing solvent protocols for different assay targets.