Using UPLC-LTQ-Orbitrap-MS and HPLC-CAD to Identify Impurities in Cycloastragenol, Which Is a Pre-Clinical Candidate for COPD oleh Feng Zhu, Xiao Zhang, Bing-Yuan Du, Xiang-Xia Zhu, Gui-Fang Zhao, Ying Sun, Qing-Qiang Yao, Hong-Bao Liang, Jing-Chun Yao, Zhong Liu, Gui-Min Zhang, Guo-Fei Qin