Application of Infrared Spectrophotometer in Drug Analysis

The domestically produced TJ270-30A infrared spectrophotometer and infrared spectrophotometer are samples that are analyzed with infrared radiation of a certain frequency. If the vibration frequency of a certain group in the molecule is the same as that of infrared radiation, resonance occurs. The cluster absorbs infrared light of a certain frequency and records the infrared radiation absorbed by the molecule by an instrument. The spectrum that fully reflects the characteristics of the sample composition can be obtained and the type and structure of the compound can be inferred. This instrument has been widely used in drug analysis, environmental monitoring, and chemical engineering. It can only be applied to the analysis of infrared spectrophotometer in drug analysis, and it can be shared with other members.

One application on the standard method.

Basically, a method applied to national standards shows that it is a relatively mature and stable method that is suitable for use in various laboratories across the country and can withstand repetition. He started by talking about the application of infrared spectrophotometer in the Chinese Pharmacopoeia.

Due to the strong characteristics of infrared spectroscopy, it is more reliable for material identification than ultraviolet spectroscopy, especially for the identification of samples with small differences in the active chemical structures of the samples with relatively complex chemical structures, which is far better than using other conventional physics and chemistry. Identification method. The 1977 edition of the Chinese Pharmacopoeia began to use infrared spectroscopy to identify samples. However, in the early days, dispersive infrared spectrophotometers were used, and they were gradually replaced by Fourier transform infrared spectrophotometers.

Do not think that infrared can only do the identification, of course, is currently in the "Chinese Pharmacopoeia" mainly for identification, but occasionally used for impurity inspection. In fact, infrared can also be measured, which we leave to the next chapter to speak.

With the increasing popularity of infrared spectrophotometers, the varieties used in the “Chinese Pharmacopoeia” to identify with this instrument have also increased year by year, and they have only been used to identify drug substances and to begin to identify formulations. The early identification of a drug substance was very numerous. Some varieties even reached more than a dozen identification projects. Different groups were identified by different chemical reactions. The maximum and minimum absorption was observed on the UV and even a thin layer chromatography was performed. . But with an infrared spectrophotometer, it's all right. An infrared spectrum scans down. That's right, not very clear. It is said that this idea is also studied with foreigners and it is close to the USP. The identification project in the American Pharmacopoeia of people is confirmed by infrared.

The Chinese Pharmacopoeia sample preparation method in infrared spectrometry. Gas, liquid, and solid samples can all be analyzed using infrared spectrophotometry. (Measuring gas has not been seen before, but it is also curious what), the commonly used methods are the following four kinds:

1. The tableting method is usually KBr (potassium bromide) tablets, and a few varieties are tableted with KCl (potassium chloride). The ratio of sample to KBr is generally 1:100. The amount of sample and the thickness of the tablet are It is better to obtain a light transmittance of more than 80% of the baseline, and the maximum absorption peak is about 20% of the transmittance.

2. Paste is a commonly used paste for paraffin oil. The sample is finely ground and mixed with a paste to form a paste. The test is performed between two windows.

3, the preparation of thin film method The sample can be placed directly on the salt window heating, melting after coating into a thin film, or the sample is dissolved in a volatile solvent, drip on the salt window, until the solvent evaporation film.

4. Dissolve the sample in a suitable solvent to make a 1% to 10% solution and record the spectrum in a liquid pool of 0.1 to 0.5 mm thickness. The solvent used should have the following conditions: greater solubility of solute; no absorption of the solvent in a large wavelength range; no window of corrosion liquid pool; no chemical reaction with solute, etc. Commonly used solvents are carbon disulfide, carbon tetrachloride, chloroform and cyclohexane.

In fact, in practical applications, most of the methods are tablet compression methods, that is, the solid drug is finely grounded, mixed with potassium bromide powder, compressed, and placed in a sample cell for scanning. Some oily drugs are smeared on pressed potassium bromide tablets and placed in a sample cell for scanning.

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