Paraformaldehyde solution

Nimodipine was purchased from Kangmanlin Chemical Industry Co., Ltd (Nanjing, China). Nitrendipine, used as an internal standard, was purchased from the National Institute of Food and Drug Control (Beijing, China). Twenty percent (w/w) aqueous injectable emulsion (long-chain oil: medium-chain oil, 1:1, w/w) was purchased from Baxter Qiaoguang Healthcare Co., Ltd (Guangzhou, China). Nimotop injection (10 mg/50 mL) was purchased from Bayer Pharma AG. PEG400 was obtained from Well Chemical Co., Ltd (Nanjing, China). Five percent glucose solution injection and 0.9% sodium chloride injection were purchased from Tianrui Pharmaceutical Co., Ltd (Zhejiang, China). Two percent 2,3,5-triphenyl tetrazolium chloride, 4% paraformaldehyde solution, and 10% paraformaldehyde were purchased from Yuanye Biotechnology Co., Ltd (Shanghai, China). Heparin sodium salt, chloral hydrate, diethyl ether, and n-hexane were of AR grade and were purchased from Sinopharm Chemical Reagent Co., Ltd. Methanol (HPLC grade) and acetonitrile (HPLC grade) were purchased from Thermo Fisher (China) Co., Ltd. All other chemical reagents were of analytical grade or chromatographic grade.