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本文报告了一种用于红外光谱定量分析的比例方法,并用此法测定了喜树碱半缩酮(Ⅱ)中少量喜树碱(Ⅰ)的含量。在红外光谱中,Ⅱ有一内酰胺羰基谱带,Ⅰ有一内酰胺羰基谱带和另一内酯羰基谱带。由于此二化合物结构类似,分子量接近,按Beer定律推导,在Ⅱ中有少量Ⅰ时,红外光谱中内酯羰基谱带吸光度与内酰胺羰基谱带吸光度之比(R)应与Ⅰ的含量(C_I)成正比。实验结果证明,以R对C_I作图所得之标准曲线通过原点,线性关系良好。测定时系用KBr压片,样品无需称量。本法操作简便,结果稳定,误差小于2％。
This article reports a proportional method for the quantitative analysis of infrared spectra and uses this method to determine the content of a small amount of camptothecin (I) in camptothecin ketals (II). In the infrared spectrum, II has a lactam carbonyl band, and I has a lactam carbonyl band and another lactone carbonyl band. Since these two compounds are similar in structure and have similar molecular weights, according to Beer’s law, when there is a small amount of I in II, the ratio of absorbance of the lactone carbonyl band in the infrared spectrum to the absorbance of the lactam carbonyl band (R) should be equal to the content of I ( C_I) is proportional to. The experimental results show that the standard curve obtained by plotting R versus C_I passes through the origin and the linear relationship is good. The measurement was made with KBr tablets and the sample did not need to be weighed. This method is easy to operate, results are stable, and the error is less than 2%.