红外(IR)光谱是液体物质定性分析的重要工具。 液体IR光谱常用液膜法制样、 透射(TR)法测试, 所需用的盐窗价格昂贵、 易受力或受潮开裂且表面清洁不彻底或划伤容易造成测试干扰, 而且可拆卸液体池安装麻烦, 进样时混入空气也会造成测试干扰。 研究液体物质红外光谱的简便测试方法, 比较改进的TR法(用在一次性压制的KBr片上涂覆液体的涂片法制样)与衰减全反射(ATR)法在液体IR光谱测试中的优劣。 选取6种挥发性、 吸水性、 腐蚀性不同的液体试剂, 采用改进的TR法和ATR法测试其IR光谱, 比较两种方法所测谱图, 并与SDBS谱库中谱图进行比较; 同时研究扫描次数和分辨率对ATR法测试谱图的影响。 结果发现, 两种方法用于液体IR的定性分析都很准确。 改进的TR法简化了制样过程且避免了清洁盐窗, 降低了成本, 但水的干扰仍难以避免; 相比之下, ATR法无需制样, 更简便、 快速, 水的干扰基本可以忽略, 虽然谱图的整体强度和精细程度不如TR法, 但通过提高分辨率、 增加扫描次数可得到高质量的谱图。 对于易挥发液体, 用改进的TR法和ATR法测试时需加大液体用量; 对于强酸性和/或腐蚀性液体, 建议采用改进的TR法测试; 对于吸湿性液体, 用ATR法测试的谱图更容易解析。 相比之下, 除强酸性和/或腐蚀性液体外, 其余液体物质皆可用ATR法快速完成IR光谱的准确检测。

Infrared (IR) spectroscopy is an important tool for the qualitative analysis of liquid matters. IR spectroscopy of liquid samples is commonly prepared by liquid film method and tested by transmission (TR) method, while the salt window required is expensive, prone to force or moisture cracking. The incomplete surface cleaning or scratches can easily cause test interference; moreover, installing the demountable liquid cells is troublesome, and mixing the trapped air into the sample will also cause test interference. In this paper, a simple method for measuring IR spectra of liquid substances is studied. The differences between the improved TR method, samples prepared by smearing method of directly coating liquid onto a single-use compressed potassium bromide (KBr) disc, and the attenuated total reflection (ATR) method in IR spectra of liquid substances are compared. 6 kinds of liquid reagents with different volatility, hygroscopicity and corrosivity were selected as the research objects, and their IR spectra were tested by both the improved TR method and ATR method. The IR spectra measured by the two methods were compared with those in the SDBS spectral database. The influence of scanning times and resolution on ATR spectra was also studied. The results show that the two methods are accurate in the IR qualitative analysis of liquid samples. The improved TR method simplifies the sample preparation process, avoids the problem of cleaning salt window, and reduces the cost, but water interference is still difficult to avoid. In contrast, the ATR method requires no sample preparation, is more simple, convenient and faster, and the interference of water is negligible. Although the overall intensity and fineness of the spectra tested by the ATR method are not as good as tested the TR method, the high-quality spectra can be obtained by improving the resolution and increasing the scanning times. The amount of liquid should be increased when using the improved TR method and ATR method for volatile liquids. The improved TR method is recommended for strongly acidic and/or corrosive liquids. For hygroscopic liquids, the spectra measured by the ATR method are easier to analyze. In contrast, except for strongly acidic and/or corrosive liquids, the other liquid substances can be rapidly and accurately tested by the ATR method.