应用高效液相色谱-飞行时间质谱法研究了β-内酰胺酶对阿莫西林降解反应的规律。采用SB-C18色谱柱分离,以不同比例的0.1%(φ)甲酸溶液和乙腈作为流动相进行梯度洗脱。质谱分析采用电喷雾正离子扫描方式。结果表明:① 7 U的β-内酰胺酶可降解10 μg阿莫西林;② 温度为15 ℃~30 ℃时,降解反应时间为2.5 h,阿莫西林的降解产物主要为阿莫西林噻唑酸(Ⅰ),超过40 ℃时,降解产物为脱羧阿莫西林噻唑酸(Ⅱ);③ 在牛奶样品中,pH为2~3时,主要为Ⅱ;pH为3~4时,Ⅰ的量逐渐增加,Ⅱ的量无大变化;当pH 7时,阿莫西林全部降解,主要为Ⅰ。

The regularity of degradation of amoxillin (AMXL) by its reaction with β-lactamase (β-LTM) was studied by HPLC-TOF-MS. SB-C18 column was used as stationary phase in the chromatographic separation, and mixtures of 0.1% (φ) HCOOH solution and acetonitrile in various ratios were used as mobile phase in gradient elution. Mode of scanning under ESI+ was adopted in MS analysis. It was found that: ① for degradation of 10 μg of AMXL, 7 U of β-LTM was necessary in the reaction; ② the optimum temperature for the degradation was found in the range of 15 ℃-30 ℃, giving reaction time of 2.5 h, the main degradation product is amoxilloic acid (abbr. as Ⅰ), and when the temperature is higher than 40 ℃, another product, the decarboxylated amoxilloic acid (abbr. as Ⅱ) is produced; ③ and it was shown that in a milk sample when acidity was adjusted to pH 2-3, Ⅱ was the main product; when at pH 3-4, amount of Ⅰ was increased gradually while amount of Ⅱ was kept nearly unchanged; and AMXL was completely degraded at pH 7 giving mainly Ⅰ.