中药白矾与伪品铵明矾的中红外光谱快速鉴别

目的 确定白矾、伪品铵明矾及两者混合物的中红外光谱鉴别特征峰，建立一种简捷、低碳的白矾真伪鉴别与铵盐检查方法。方法 使用衰减全反射法直接测量白矾、铵明矾及两者混合物的中红外光谱，寻找白矾与铵明矾的差异吸收峰并进行统计分析，评价通过差异吸收峰区分白矾与铵明矾、识别白矾中掺入铵明矾的可行性。结果 中红外光谱上白矾与铵明矾的主要差异在于后者具有1436 cm^–1附近的铵离子N-H弯曲振动峰，根据该特征峰的有无可以直观区分白矾与铵明矾。白矾中铵明矾掺入量不低于5%时，根据N-H弯曲振动峰的高度或面积可以定性识别铵离子，达到《中华人民共和国药典》2020年版规定的白矾检查项中铵盐检出限要求。结论 中红外光谱能够准确鉴别白矾、铵明矾与两者混合物，可以作为一种简便、快速、费用低、绿色的白矾真伪鉴别与铵盐检查方法。

Rapid Identification of Traditional Chinese Medicine Alumen and the Counterfeit Ammonium Alum by Mid-infrared Spectroscopy

Objective The mid-infrared (MIR) spectroscopic characteristic peaks were determined for the discrimination of Alumen, ammonium alum and their mixture to establish a simple and low-carbon method for the identification of Alumen and the examination of ammonium salt in Alumen.Methods MIR spectra of Alumen, ammonium alum and their mixtures were directly measured by the attenuated total reflection method. The differential absorption peaks between Alumen and ammonium alum were examined. The feasibility of the differential absorption peaks to discriminate Alumen and ammonium alum as well as to detect the adulterated Alumen with ammonium alum was evaluated by statistical analysis.Results The mian difference in MIR spectra between Alumen and ammonium alum was that there was the N-H bending vibration peak of ammonium ions near 1436 cm^–1 in the latter. Alumen and ammonium alum could be discriminated intuitively according to the presence or absence of this characteristic peak. Ammonium ion can be qualitatively identified based on the height or area of the N-H bending vibration peak when Alumen was adulterated with not less than 5% of ammonium alum, meeting the requirement for the limit of detection of ammonium salt in the Section of Alumen Detection in Chinese Pharmacopoeia (version 2020).Conclusion MIR spectroscopy can accurately identify Alumen, ammonium alum and their mixtures, and can be used as a simple, rapid, cheap and green method for the identification of Alumen and the examination of ammonium salt in Alumen.