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建立了在线二维液相色谱-四极杆飞行时间质谱检测头孢噻吩钠杂质谱的方法，有效地解决了流动相中含不挥发性磷酸盐的色谱系统不适合用于液相色谱-质谱快速鉴定杂质的难题。一维高效液相色谱（ HPLC）以 Symme-try C18为色谱柱，以磷酸盐缓冲液（ pH 2.5）和乙腈梯度洗脱；二维以 ACQUITY UPLC BEH C18为色谱柱，以0.1％（ v／v）甲酸水溶液和0.1％（ v／v）甲酸乙腈溶液梯度洗脱。以 HLB C18为捕集柱，用0.1％（ v／v）甲酸水溶液进行捕集和脱盐，采用正离子模式采集数据。对头孢噻吩钠中6个杂质进行了结构鉴定，对其来源进行了分析，并进一步确证了《中国药典》2010年版对头孢噻吩钠杂质 A认定有误。采用本方法可以快速、简便、灵敏地对头孢噻吩钠杂质谱进行检测。

A two-dimensional liquid chromatography-quadrupole time-of-flight mass spectrome-try(2D-LC-QTOF MS)method to profile the impurities of cefalotin sodium was developed. A Symmetry C18 column(250 mm×4. 6 mm,5 μm)was used in the first dimensional chromatog-raphy,with gradient elution using pH 2. 5 phosphate buffer and acetonitrile as the mobile pha-ses. The column temperature was maintained at 40 ℃ with an ultraviolet detection of 220 nm for analysis. An ACQUITY UPLC BEH C18 column(50 mm×2. 1 mm,1. 7 μm)was used in the sec-ond dimensional chromatography,with gradient elution using water containing 0. 1%( v/v)for-mic acid and acetonitrile containing 0. 1%( v/v)formic acid as the mobile phases. The column temperature was maintained at 40 ℃. An HLB C18 column(30 mm×2. 1 mm,20 μm)was used as the trap column. The data were collected in positive ion mode. The ion source temperature was set at 100 ℃ and the electrospray ionization( ESI)needle voltage was set at 1 000 V. The nebulizer gas temperature was set at 500 ℃. The molecular formulas of the impurities were determined by their exact masses and isotope distributions. And the structures were determined by the protonated molecular ions and the manufacturing process of cefalotin sodium. Six impu-rities of cefalotin sodium were characterized and the origination of the impurities was deduced. Three of them were unknown impurities to the best of our knowledge. It was confirmed that the Chinese Pharmacopoeia 2010 has mistaken impurity A of cefalotin sodium. The results indicated that the 2D-LC-QTOF MS method could be used to investigate the impurity profile of cefalotin sodium,and it is simple and sensitive.