What are the precautions for testing samples with an infrared spectrometer?

The following matters should be paid attention to when using infrared spectrometer to test samples: 1. Pay attention to the use of specified environmental conditions, and it is worth trusting that infrared spectrometer manufacturers remind us to pay attention to the temperature and relative humidity of the laboratory should be within the standard range, and the power supply used should be equipped with a voltage stabilizing device and a grounding wire. In order to better control these conditions, the area of the infrared laboratory should not be too large, and the necessary instruments and equipment can be placed, but there must be a dehumidification device in the room.

In addition, the CO2 content in the laboratory should not be too high, so the number of people in the laboratory should be as small as possible, and it is best not to enter irrelevant personnel, and pay attention to proper ventilation.

2. In order to prevent the service life of the instrument from being affected by moisture, infrared spectrometer merchants emphasize that the infrared laboratory should be kept dry frequently, even if the instrument is not in use, it should be turned on at least twice a week, half a day each time, and the dehumidifier should be opened at the same time for dehumidification. Especially during the mildew season, it is best to turn on the dehumidifier every day. In addition, the sample used for measurement by infrared spectrometer should be dried, otherwise it should be dried under an infrared lamp for a few minutes after grinding.

After the sample is ground and installed in the mold, it should be connected to the vacuum pump and vacuumed for at least 2 minutes to further remove the water in the sample, and then pressurized to a certain standard for a few minutes.

3. Note that when using the infrared spectrometer, if the test sample is hydrochloride, it is necessary to take into account the ion exchange phenomenon that may occur in the tableting process. Infrared spectrometer vendors emphasize that the standard stipulates that potassium chloride (also used after pretreatment like potassium bromide) is used instead of potassium bromide for tableting, but it is also possible to compare the spectra measured after potassium chloride tableting and potassium bromide tableting, and if there is no difference between the two, potassium bromide can be used for tableting.

1. The temperature of the laboratory should be 15 30, the relative humidity should be below 65%, and the power supply used should be equipped with a voltage stabilizing device and a grounding wire. Because the relative humidity in the room should be strictly controlled, the area of the infrared laboratory should not be too large, and the necessary instruments and equipment can be placed, but there must be a dehumidification device in the room. 2. If the single gill type FTIR spectrophotometer is used (currently the most used), the CO2 content in the laboratory should not be too high, so the number of people in the laboratory should be as small as possible, and it is best not to enter irrelevant personnel, and pay attention to proper ventilation.

3. If the test product is hydrochloride, due to the ion exchange phenomenon that may occur in the tableting process, the standard stipulates that potassium chloride (also used after pretreatment like potassium bromide) is used instead of potassium bromide for tableting, but the spectrum measured after potassium chloride tableting and potassium bromide tableting can also be compared, if there is no difference between the two, potassium bromide can be used for tableting.

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The infrared spectrometer mainly detects: it can determine the existence or change of functional groups or chemical bonds in the sample, which is used to study the qualitative, quantitative, and reaction processes of substances.

In general, inorganics need to be detected with a far-infrared spectrometer. Because most of the vibrational peaks of inorganic matter are in the far infrared band, the detection range of the commonly used infrared spectrometer is in the mid-infrared region.

If an infrared spectrometer is needed to detect the infrared spectrum of inorganic matter, the spectrometer needs to be adjusted, the beam splitter in the Michelson interferometer and the detector of the spectrometer need to be replaced.

Principle:

The Fourier transform infrared spectrometer is known as the third-generation infrared spectrometer, which uses a McKelson interferometer to interfere with two multichromatic infrared lights with a certain speed difference in optical path to form interference light, and then interact with the sample. The detector sends the obtained interference signal to the computer for mathematical processing of the Fourier change, and the interference pattern is restored to a spectral pattern.

The characteristic absorption of functional groups of organic compounds can be referred to the organic spectroscopy book.

4000-1300 is used to identify functional groups, and 1300-400 is a fingerprint area, which is used to identify compounds with similar structures, and can also be used as circumstantial evidence for the presence of a certain group in a compound. The common characteristic absorption frequencies are: 3200-3650 hydroxyl group, free state in 3610-3640 peak type sharp, intermolecular association in 3300, broad peak.

More than 3000 is the unsaturated c-h expansion vibration, 3300 is a typical terminal alkyne, less than 3000 is the saturated c-h expansion vibration, the strong absorption peak of about 1700 indicates the existence of c=o, 1600, 2-4 peaks near 1500, is the skeleton vibration of the aromatic ring, and for more detailed explanation, please refer to Ning Yongcheng's organic compound structure identification and organic popology, a very good book

Infrared detection of characteristic functional groups of organic matter.

Infrared spectroscopy can study the structure and chemical bonds of molecules, such as the determination of force constants and molecular symmetry, etc., and the bond length and bond angle of molecules can be determined by infrared spectroscopy, and the three-dimensional configuration of molecules can be inferred. According to the obtained force constant, the strength of the chemical bond can be deduced, and the thermodynamic function can be calculated from the simple frequency. Some groups or chemical bonds in the molecule correspond to the band wavenumber in different compounds are basically fixed or only change in the small wavelength range, so many organic functional groups such as methyl, methylene, carbonyl, cyano, hydroxyl, amine and so on have characteristic absorption in the infrared spectrum, through infrared spectroscopy, people can determine which organic functional groups exist in the unknown sample, which lays the foundation for the final determination of the chemical structure of the unknown.

<> requirements are as follows: 1. The sample must be pre-purified to ensure sufficient purity;

2. The sample must be dried in advance to avoid damage to the instrument and avoid the interference of the water peak on the sample spectrum;

3. Samples that are easily deliquescent should be placed in the dryer;

4. For volatile, sublimation, and thermally unstable samples, please use a container with a sealed lid or stopper and close it tightly, and it must be indicated;

5. For toxic and corrosive samples, the user must pack them in sealed containers, and the samples must be indicated in the obvious position of the sample vial label when sending the samples.

The requirements for the sample when determining the infrared absorption light trillion spectrum are as follows:

1. The sample must be pre-purified to ensure that there is enough pure wheel grinding.

2. The sample must be dried in advance to avoid damage to the instrument, and avoid the interference of the water peak on the sample spectrum when the same family is a brother.

3. Samples that are easily deliquescent should be placed in the dryer;

4. For volatile, sublimation, and thermally unstable samples, please use a container with a sealed lid or stopper and close it tightly, and it must be indicated;

5. For toxic and corrosive samples, the user must pack them in a sealed container. Samples must be sent in a conspicuous position on the vial label.

About infrared absorption spectroscopy

Infrared spectroscopy is used to analyze and identify substance molecules. A beam of infrared rays of different wavelengths is irradiated to the molecules of a substance, and some specific wavelengths of infrared rays are absorbed, forming the infrared absorption spectrum of this molecule. Each molecule has a unique infrared absorption spectrum determined by its composition and structure, from which the structure of the molecule can be analyzed and identified.

Infrared absorption spectroscopy is produced by the constant vibration and rotational motion of molecules, molecular vibration refers to the relative movement of atoms in the molecule near the equilibrium position, and polyatomic molecules can form a variety of vibrations. When each primordial mill in the molecule vibrates at the same frequency and in the same phase near the equilibrium position, this vibration mode is called simple normal vibration (such as telescopic vibration and variable angle vibration).

The energy of molecular vibration corresponds to the optical quantum energy of infrared rays, so when the vibrational state of the molecule changes, the infrared spectrum can be emitted, and the infrared absorption spectrum can also be generated due to the vibration of the molecule excited by infrared radiation.

The energy of the vibration and rotation of the molecule is not continuous but quantized. However, due to the rotational transition in the process of the vibrational transition of the molecule, the vibrational spectrum is banded. Therefore, the infrared spectrum of the molecule belongs to the strip spectrum. The larger the molecule, the more infrared bands.

Basic operation steps of the infrared spectrometer:

1. Turn on the power switch of the infrared spectrometer.

2. Click on the computer screen to open the IRSort workstation software.

3. Click Measure to make the screen go to the measurement interface. After that, the instrument is initialized.

4. Prepare potassium bromide blanks and sample compressions.

5. Put the pressed potassium bromide blank (potassium bromide blank without sample) into the sample rack in the sample compartment of the spectrometer.

6. Click the background button under the measurement button, enter the spectrum name, and confirm the background spectrum of the reference spectrum.

7. After the background spectrum is collected, put the sample piece to be measured into the spectrometer and close the compartment cover.

8. The software can carry out various analysis and processing of the spectrum as required, select print from the file menu, and print the spectrum in different forms.

9. Exit the system.

2. Precautions for the use of the instrument.

1. The instrument must be installed on a stable and firm test bench, away from the vibration source.

2. The test sample should be taken out in time after the test is completed, and it will pollute the optical system and cause performance degradation if placed in the sample chamber for a long time. The sample chamber should be kept dry and the desiccant should be replaced in time.

3. Keep the reagents and samples used dry, and put them into the dryer in time after use.

4. During work, the power should not be cut off halfway.

5. Infrared accessories such as tablet molds and liquid absorption pools should be wiped clean in time after use, cleaned if necessary, and stored in a dryer to avoid rust.

6. There is a laser in the optical path, and it is strictly forbidden for eyes to enter the optical path when the machine is turned on.

7. After the measurement is completed, the instrument use registration record should be made in time.