红外分光光度法

红外吸收分光光度法
2.2.24. ABSORPTION SPECTROPHOTOMETRY, INFRARED
红外光谱频率在4000～670 cm-1之间（2.5～15.4μm），有时也低至200cm-1 (50μm) 。

Infrared spectrophotometers are used for recording spectra in the region of 4000-650 cm−1 (2.5-15.4 μm) or in some cases down to 200 cm−1(50 μm).
仪器设备原理
APPARATUS
记录光谱的分光光度计是由一个合适的光源，单色仪或干涉仪和检测器组成的。

傅立叶变换红外分光光度计使用复色光源，利用傅立叶变换计算出随入射光频率变化的原始光谱。

也可以使用其他检测领域中配有单色光源系统的红外分光光度计。

通常由对比透射光和入射光的强度来获得光谱。

Spectrophotometers for recording spectra consist of a suitable light source, monochromator or interferometer and detector. Fourier transform spectrophotometers use polychromatic radiation and calculate the spectrum in the frequency domain from the original data by Fourier transformation. Spectrophotometers fitted with an optical system capable of producing monochromatic radiation in the measurement region may also be used. Normally the spectrum is given as a function of transmittance, the quotient of the intensity of the transmitted radiation and the incident radiation. It may also be given in absorbance.
吸光率（A）值为透光率（T）的倒数取log10对数的值。

T=I
I0
I0 =入射光强度
I = 透射光强度
Theabsorbance(A) is defined as the logarithm to base 10 of the
reciprocal of the transmittance (T):
,
T=I
I0
I0 = intensity of incident radiation,
I = intensity of transmitted radiation.
制备样品
PREPARATION OF THE SAMPLE
记录吸光率或透光率
FOR RECORDING BY TRANSMISSION OR ABSORPTION
用下列方法制备样品。

Prepare the substance by one of the following methods.
液体：制成两盐片间的液膜或由透明的液体池盛装的样品，也可以直接用红外光照射待测液体。

Liquids. Examine a liquid either in the form of a film between 2 plates transparent to infrared radiation, or in a cell of suitable path length, also transparent to infrared radiation.
悬浊液或乳浊液
Liquids or solids in solution.
用适合的溶剂溶解样品。

选择合适的浓度和液体池光程以便得到满意的光谱。

通常，液体浓度为10～100g/l，液体池光程为0.1～0.5mm。

在参比光路中放入与溶液相同的溶剂池以补偿溶液中溶剂的吸收。

如果使用傅里叶变换的红外光谱仪，可以先记录下溶剂以及样品的光谱图，然后通过软件，利用溶剂的系数扣除溶剂的吸收部分。

Prepare a solution in a suitable solvent. Choose a concentration and a path length of the cell which give a satisfactory spectrum. Generally, good results are obtained with concentrations of 10-100 g/L for a path length of 0.5-0.1 mm. Absorption due to the solvent is compensated by placing in the reference beam a similar cell containing the solvent used. If an FT-IR instrument is used, the absorption is compensated by recording the spectra for the solvent and the sample successively. The solvent absorbance, corrected by a compensation factor, is subtracted using calculation software.
固体
使待检物质分散在适合的溶液中（研磨），或者分散在固体中（卤化物压片）；根据专论要求，将熔融的待检物质滴在两盐片之间制成薄膜，然后测定光谱。

Solids. Examine solids dispersed in a suitable liquid (mull) or in a solid (halide disc), as appropriate. If prescribed in the monograph, make a film of a molten mass between 2 plates transparent to infrared radiation.
A研磨法
用少量样品粉末加少量石蜡或者其他适合的液体研磨；通常用5～10mg样品加1滴石蜡研磨，磨好后压入两盐片之间测定光谱。

A. Mull
Triturate a small quantity of the substance to be examined with the minimum quantity of liquid paraffin R or other suitable liquid; 5-10 mg of the substance to be examined is usually sufficient to make an adequate mull using one drop of liquid paraffin R. Compress the mull between 2 plates transparent to infrared radiation.
B压片法
除非另有规定，1～2mg待检测物质加300～400mg干燥的溴化钾或氯化钾细粉，共同磨碎。

通常该量的样品足够成压成一个直径为10~15 mm压片，并得到合适的光谱强度。

如果检测物质是盐酸盐，推荐使用氯化钾。

仔细磨碎混合物，均匀的铺在模子里,在800MPa(8 t·cm−2)压力下压片。

导致坏片的原因很多，如过多或太少的研磨，吸潮，分散媒介物中有其他杂质，没有进行充分研磨和颗粒的尺寸不够小等。

除非另有规定，不好的压片要弃用：用肉眼观察，压片的透明度不均匀；或没有补偿的情况下，在2000cm-1 (5 µm)左右缺少特殊吸收带，透光率低于60%。

B. Disc
Triturate 1-2 mg of the substance to be examined with 300-400 mg, unless otherwise specified, of finely powdered and dried potassium bromide R or potassium chloride R. These quantities are usually sufficient to give a disc of 10-15 mm diameter and a spectrum of suitable intensity. If the substance is a hydrochloride, it is recommended to use potassium chloride R. Carefully grind the ixture, spread it uniformly in a suitable die, and submit it to a pressure of about 800 MPa (8 t·cm−2). For substances that are unstable under normal atmospheric conditions or are hygroscopic, the disc is pressed in vacuo. Several factors may cause the formationoffaultydiscs,suchasinsufficientorexcessive grinding, humidity or other impurities in the dispersion medium or an insufficient reduction of particle size. A disc is rejected if visual examination shows lack of uniform transparency or when transmittance at about 2000 cm−1 (5 μm)
in the absence of a specific absorption band is less than 60 per cent without compensation, unless otherwise prescribed.
气体
气体样品在光程100mm的气体池中测试，通过适合的活塞或针形阀门（连接在盛有被检测气体的容器和吸收池之间），抽空吸收池中的气体，注入规定压力的被检测气体。

Gases.
Examine gases in a cell transparent to infrared radiation and having an optical path length of about 100 mm. Evacuate the cell and fill to the desired pressure through a stopcock or needle valve using a suitable gas transfer line between the cell and the container of the gas to be examined.
必要时，加入惰性非红外活性气体（例如，氮气或氩气），调节气体池压力为大气压，再进行红外检测。

检测过程中，要注意避免水，二氧化碳或空气中其他气体的吸收干扰，如果条件允许，在参比光路中放入与样品相同的抽空或充有非红外活性气体吸收池，进行红外检测。

If necessary adjust the pressure in the cell to atmospheric pressure using a gas transparent to infrared radiation (for example nitrogen R and argon R). To avoid absorption interferences due to water, carbon dioxide or other atmospheric gases, place in the reference beam, if possible, anidenticalcell that is either evacuated or filled with the gas transparent to infrared radiation.
记录漫反射系数
FOR RECORDING BY DIFFUSE REFLECTANCE
固体。

加入约5%的检测物质的干燥的溴化钾或氯化钾，碾磨，除非另有规定。

研磨混合后，放置在一个样品杯进行反射光谱的检查。

Solids. Triturate a mixture of the substance to be examined with finely powdered and dried potassium bromide R or potassium chloride R. Use a mixture containing approximately 5 per cent of the substance, unless otherwise specified. Grind the mixture, place it in a sample cup and examine the reflectance spectrum.
所得的频谱进行Kubelka - Munk函数的数学处理后可以得到样品吸光度模式的光谱。

The spectrum of the sample in absorbance mode may be obtained after mathematical treatment of the spectra by the Kubelka-Munk function.
记录衰减全反射
FOR RECORDING BY ATTENUATED TOTAL REFLECTION
衰减全反射（包括多次反射）通常通过内部传输介质来实现。

而且某些附件只有一次反射发生。

Attenuated total reflection (including multiple reflection) involves light being reflected internally by a transmitting medium, typically for a number of reflections. However, several accessories exist where only one reflection occurs.
按以下方法制备样品。

将需要研究物质内部反射的供试品与衰减全反射比棱镜紧密接触，比如钻石，锗，硒化锌，溴化铊，碘化铊（KRS- 5）或其他高折射率的材料等样品。

可以通过施加压力使供试品与棱镜的紧密接触，或者使用适当的溶剂溶解供试品然后蒸发至干来确保供试品与棱镜的紧密接触。

扫描衰减全反射（ATR）的光谱。

Prepare the substance as follows. Place the substance to be examined in close contact with an internal reflection element (IRE) such as diamond, germanium, zinc selenide, thallium bromide-thallium iodide (KRS-5) or another suitable material of high refractive index. Ensure close and uniform contact between the substance and the whole crystal surface of the internal reflection element, either by applying pressure or by dissolving the substance in an appropriate solvent, then covering the IRE with the obtained solution and evaporating to dryness. Examine the
attenuated total reflectance (ATR) spectrum.
利用参照物质鉴别
IDENTIFICATION USING REFERENCE SUBSTANCES
待检测物质和参照物质以同样的方法制样，相同操作条件下检测4000～650cm-1的（2.5～15.4 µm）范围内红外光谱。

将检测物质光谱的最小透光值（最大吸收值）所处的位置和尺寸与参照物质（CRS）的光谱进行比较。

Prepare the substance to be examined and the reference substance by the same procedure and record the spectra between 4000-650 cm−1 (2.5-15.4 μm) under the same operational conditions. The transmission minima (absorption maxima) in the spectrum obtained with the substance to be examined correspond in position and relative size to those in the spectrum obtained with the reference substance (CRS).
当固体样品光谱的最小透光值（最大吸收值）所处的位置与参照物质光谱不同时，用同种方法处理样品和参照物质，使它们能够形成同样的结晶或形态，或按照专论规定的方法进行操作，然后记录光谱。

When the spectra recorded in the solid state show differences in the positions of the transmission minima (absorption maxima), treat the substance to be examined and the reference substance in the same manner so that they crystallise or are produced in the same form, or proceed as prescribed in the monograph, then record the spectra.
利用标准光谱鉴别
IDENTIFICATION USING REFERENCE SPECTRA
分辨性能的控制
Control of resolution performance.
对于色散形光谱仪，记录约35µm厚的聚苯乙烯膜的光谱。

参见图2.2.24-1，在2870 cm-1(3.48 µm)处的最大透光率百分比A与2849.5cm-1(3.51um)处的最小透光率百分比B之间的差值x 必须大于18；在1589cm-1(6.29um)处的最大透光率百分比C与1583 cm-1（6.32um）处的最小透光率百分比D之间的差值y，必须大于10。

For instruments having a monochromator, record the spectrum of a polystyrene film approximately 35 μm in thickness. The difference x (see Figure 2.2.24.-1) between the percentage transmittance at the transmission maximum A at 2870 cm−1 (3.48 μm) and that at the transmission minimum B at 2849.5 cm−1 (3.51 μm) must be greater than 18. The difference y between the percentage transmittance at the transmission maximum C at 1589 cm−1 (6.29 μm) and that at the transmission minimum D at 1583 cm−1 (6.32 μm) must be greater than 10.
傅立叶变换光谱仪，制造商使用了合适的部件对吸收光谱进行了适当变迹。

这种方式被得到了验证。

记录约35µm厚的聚苯乙烯膜的光谱。

在2870 cm - 1处的最小吸光度和2849.5 cm-1的最大吸光度之间的差值大于0.33。

在1589cm-1的最小吸光度和1583cm-1的最大吸光度之间的差值大于0.08。

For Fourier-transform instruments, use suitable instrument resolution with the appropriate apodisation prescribed by the manufacturer. The resolution is checked by suitable means, for example by recording the spectrum of a polystyrene film approximately 35 μm in thickness. The difference between the absorbances at the absorption minimum at 2870 cm−1 and the absorption maximum at 2849.5 cm−1 is greater than 0.33. The difference between the absorbances at the absorption minimum at 1589 cm−1 and the absorption maximum at 1583 cm−1 is greater than 0.08.
图2.2.24-1 聚苯乙烯红外光谱图
较验波数范围
Verification of the wave-number scale.
以聚苯乙烯膜校验波数范围，其最小透光率（最大吸光率）的波数见表2.2.24.-1。

The wave-number scale may be verified using a polystyrene film, which has transmission minima (absorption maxima) at the wave numbers (in cm–1) shown in Table 2.2.24.-1.
表2.2.24.-1.聚苯乙烯膜的最小透光率波数及可接受范围
方法根据参照光谱/参照物质的要求制备样品。

按照参照光谱的操作条件（通常为校验分辨率的操作条件）操作，检测并记录样品光谱图。

Method. Prepare the substance to be examined according to the instructions accompanying the reference spectrum/reference substance. Using the operating conditions that were used to obtain the reference spectrum, which will usually be the same as those for verifying the resolution performance, record the spectrum of the substance to be examined.
样品光谱的吸收带位置和尺寸应和参照光谱一致。

The positions and the relative sizes of the bands in the spectrum of the substance to be examined and the reference spectrum are concordant in the 2 spectra.
水蒸气和空气中二氧化碳的补偿
Compensation for water vapour and atmospheric carbon dioxide.
通过生产厂家所提供的使用说明对光谱进行傅里叶变换，可以解决水蒸气和二氧化碳的干扰问题。

同样，通过使用适当的清除部件或者确保样品和单光束的背景完全相同的条件下，亦可以达到相同的效果
For Fourier-transform instruments, spectral interference from water vapour and carbon dioxide is compensated using suitable algorithms according to the manufacturer’s instructions. Alternatively, spectra can be acquired using suitable purged instruments or ensuring that sample and background single beam spectra are acquired under exactly the same conditions.
气体中的杂质
IMPURITIES IN GASES
分析气体中的杂质，选择适合光程（例如1～20cm）的气体池，按气体项下的规定充满待测气体，进行红外检测。

根据专论中规定的方法进行杂质检测与定量。

For the analysis of impurities, use a cell transparent to infrared radiation and of suitable optical path length (for example, 1-20 m). Fill the cell as prescribed under Gases. For detection and quantification of the impurities, proceed as prescribed in the monograph.。