气相色谱-质谱法测定祛痘化妆品中4种硝基咪唑类化合物

Quantitative Determination of 4 Nitroimidazoles in Acne Cosmetics by Gas Chromatography-Mass Spectrometry

建立了同时测定祛痘化妆品中4种硝基咪唑类化合物（甲硝唑、奥硝唑、洛硝唑和塞克硝唑）的气相色谱-质谱联用（GC-MS）分析方法。样品用碳酸钠溶液溶解后以乙酸乙酯提取,经浓缩和（或）正己烷除脂后,用N,O-双（三甲基硅烷基）乙酰胺衍生,样液经DB-5 MS（30 m×0.25 mm×0.25μm）毛细管色谱柱分离,GC-MS的选择离子监测（SIM）模式检测,以保留时间和特征离子比值定性,同位素内标法定量。结果表明,4种硝基咪唑类化合物在0.10-5.0 mg/L范围内线性关系良好,相关系数均不小于0.998;方法检出限（S/N=3）为0.05-0.10 mg/kg;在祛痘水和祛痘膏样品中进行3个水平的加标实验,平均回收率为85.6%-104%,相对标准偏差（RSD,n=6）为2.9%-6.5%。实际样品检测表明本方法准确可靠,适用于祛痘化妆品中硝基咪唑类化合物的同时测定。

A new method was developed for the simultaneous determination of four nitroimidazoles, e.g. metronidazole （MNZ）, ornidazole （ONZ）, ronidazole （RNZ） and secnidazole （SNZ）, in acne cosmetics by gas chromatography - mass spectrometry （ GC - MS）. The samples were firstly diluted with sodium carbonate solution and then extracted with ethyl acetate. The extract was subsequently concentrated and/or the fat in which was wiped off with n-hexane. Finally, four nitroimidazoles were derivatised using N, O-bis（trimethylsilyl） -acetamide as derivating agent, and separated on a DB - 5 MS capillary chromatographic column （30 m × 0. 25 mm × 0. 25μm）. The target compounds were identified by GC - MS with retention time and ratio of the characteristic ions under selected ion monitoring（SIM） mode, and quantified by the internal standard method. The result indicated that 4 analytes had good linear relationships（ r^2≥0. 998 ） in the concentrations of 0. 10 - 5.0 mg/L. The detection limits of target compounds for this method （ LODs, S/N = 3 ） ranged from 0. 05 mg/kg to 0. 10 mg/kg. The recoveries of four nitroimidazoles at three spiked levels in acne cream and acne water samples were in the range of 85.6% - 104% , with relative standard deviations（RSDs, n = 6） of 2. 9% -6. 5%. The real sample analysis showed that this accurate and precise method could be applied in the simultaneous determination of four nitroimidazoles in acne cosmetics.