目的 建立LC-MS/MS法同时测定士的宁及其代谢物士的宁氮氧化物在大鼠血浆中的浓度。方法 以盐酸麻黄碱为内标，甲醇沉淀法处理血浆样品。采用ZORBAX Eclipse XDB-C18柱（2.1 mm×150 mm，3.5 μm）分离，以甲醇-10 mmol•L-1乙酸铵（用甲酸调pH=4）为流动相进行梯度洗脱，流速0.2 mL•min-1，用电喷雾离子化和正离子多离子反应监测（MRM）模式检测士的宁和士的宁氮氧化物。结果 士的宁及其氮氧化物的线性范围分别为0.510~306.3 ng•mL-1和0.102~306.0 ng•mL-1，定量下限分别为0.510，0.102 ng•mL-1，日内、日间相对标准偏差（RSD）均＜15 %，准确度分别为（89.44±3.43）%~（97.45±6.25）%和（95.86±5.19）%~（106.41±7.43）%。结论 该方法准确、灵敏、特异、简便，适用于血浆中士的宁及其代谢物士的宁氮氧化物含量的同时测定。

Objective To establish a liquid chromatography-mass spectrometry/mass spectrometry（LC-MS/MS） method for the simultaneous analysis of strychnine and strychnine N-oxide in rat plasma. Methods Ephedrine hydrochloride was used as the internal standard（IS）. The protein precipitation by methanol was used to extract the analytes from plasma. Chromatographic separation was carried out on ZORBAX Eclipse XDB-C18 column（2.1 mm×150 mm，3.5 μm） by gradient elution with phase A 10 mmol•L-1 ammonium acetate（adjusted to pH 4.0 with formic acid） and phase B methanol. The flow rate was 0.2 mL•min-1. The quantification of the analytes was performed by mass spectrometry with electrospray ionization（ESI） inlet and positive ion multiple reaction monitoring（MRM） mode. Results The calibration curves of strychnine and strychnine N-oxide in the plasma were linear in the range of 0.510~306.3 ng•mL-1 and 0.102~306.0 ng•mL-1，respectively. The lower limit of quantitation was 0.510 ng•mL-1 for strychnine and 0.102 ng•mL-1 for strychnine N-oxide. The inter-day and intra-day relative standard deviation（RSD） was less than 15 %. The accuracy of strychnine was（89.44±3.43） %~（97.45±6.25） % and that of strychnine N-oxide was（95.86±5.19） %~（106.41±7.43） %. Conclusion The established assay method is accurate，sensitive，specific and convenient，which is suitable for the measurement of plasma strychnine and strychnine N-oxide concentration in rats.

R285.5

广东省科技厅资助项目（2011B010500016）；2014广东省中医院拔尖人才科研专项“中药马钱子有效成分在毒性剂量下体内代谢动力学研究”。