Betulin (BE) has exceedingly become a potential natural product, providing multiple pharmacological and biological activities, including anti-cancer, anti-viral, and anti-inflammatory benefits. Previous research indicated that the solvatomorphism of BE can easily occur through crystallization with different organic solvents. This property of BE can directly affect its extraction, isolation, and preparation process. In this study, a system of thermogravimetry (TG)-differential thermal analysis (DTA) coupled with mass spectrometry (MS) with electron ionization (EI) and photoionization (PI) capability, equipped with the skimmer-type interface (i.e., skimmer-type interfaced TG-DTA-EI/PI-MS system), as a real-time and onsite analysis technique, was employed. Then, four solvatomorphs of BE, namely, with pyridine and water (A), sec-butanol (B), n,n-dimethylformamide (DMF) (C), and isopropanol (V), were analyzed for the first time. Finally, five kinds of the main volatile gaseous species, including H 2 O, pyridine, sec-butanol, DMF, and isopropanol, were identified clearly. Furthermore, the multi-step desolvation processes of the four solvatomorphs of BE were revealed by this system for the first time. This system showed great potential for the rapid and accurate analysis of various solvatomorphs of natural products.

Betulin (BE) can be obtained from many plants, such as those belonging Betulaceae family, and pharmacological investigations showed its notable biological properties and good potential for food and pharmaceutical development. We investigated the homogeneity, stability, purity, and uncertainty of a newly certified reference material (CRM) of BE. The certified purity value for the CRM of BE was 99.56% with an extended uncertainty of 0.07% (k = 2, P = 0.95), as determined by differential scanning calorimetry (DSC). In this study, DSC was used for the first time for purity determination of BE. Given its high accuracy, precision, and reproducibility, DSC can be used as an alternative technique for purity determination of CRMs in the pharmaceutical and food industry. Graphic abstract

Salvianolic acid A (Sal A), a water-soluble ingredient in Danshen, has various biological activities. Sal A and its impurities have similar physical and chemical properties, as well as strong reducibility; therefore, they are difficult to prepare and purify. In this study, high-purity Sal A was obtained by purification of sephadex chromatography and preparative chromatography. Furthermore, HPLC-DAD tandem ECD and HPLC-DAD tandem MS methods were used for non-volatile organic impurity analysis, ICP-MS method was used for non-volatile inorganic impurities and mass balance method and quantitative nuclear magnetic resonance were employed to certify the product. The structures of Sal A and its relative impurities were validated by nuclear magnetic resonance spectroscopy and mass spectrometry, and their contents were quantified as well. Following the principles of ISO Guides 34:2009 and 35:2005, a Sal A reference material was certified, covering homogeneity studies, stability studies, characterization, and uncertainty estimations. We dedicate this paper to Prof. Sun Han-Dong on the occasion of his 80th birthday.