CN1587990A - Method for analyzing beta-cyclodextrin clathrate compound by Fourier infrared spectrum method - Google Patents

Abstract

The invention discloses a method for analyzing β-cyclodextrin inclusion compound by a Fourier infrared spectrometry, which consists of three main parts: analysis principle, analysis method and steps, and result processing. In the present invention, it is found that the infrared absorption intensity of the β-cyclodextrin inclusion complex guest molecules decreases significantly after inclusion, which is called the package weakened infrared effect, which is the basis for using FT-IR to analyze the β-cyclodextrin inclusion complex. Infrared spectra of inclusion compounds and non-inclusion compounds and comparing the positions, shapes and assignments of their absorption peaks, especially calculating the change of absorption intensity, can qualitatively or quantitatively analyze and determine inclusion compounds. The advantages of the present invention are: the present invention is simple and fast, clear and intuitive, can qualitatively or quantitatively analyze and determine whether the inclusion has been included, the degree of inclusion, the mechanism of inclusion, and a large amount of information. The novel and powerful tool not only has a certain academic value, opens up a new field of infrared research and application, but also has practical application value in scientific research and production.

Description

Method for analyzing β-cyclodextrin inclusions by Fourier infrared spectroscopy

technical field

The invention relates to an analysis method of β-cyclodextrin inclusion compound, in particular to a method for analyzing β-cyclodextrin inclusion compound by Fourier infrared spectroscopy.

Background technique

β-cyclodextrin (β-Cyslodextrin, abbreviated as β-cyclodextrin) has a special cage structure, so that it can be used as a host to include various guest molecules of comparable size. Inclusion can change the physical and chemical characteristics of the state and stability of the guest molecule, and β-cyclodextrin is non-toxic, so the inclusion complex formed by β-cyclodextrin and drug and spice molecules is increasingly widely used in pharmaceutical, food and other industries middle. The analysis and determination of β-cyclodextrin inclusion complex is an important link to improve the production process and ensure product quality. At present, methods such as thermal analysis techniques DTA (differential heat), DSC (differential display), spectrophotometry and chemical analysis are generally used. The DTA method is affected by many factors, has poor reproducibility, is difficult to quantitatively analyze, and is time-consuming; for example, it takes 35-70 minutes to reach 350°C at a heating rate of 5-10°C/min. In addition, during 1994-2004, there was no domestic report on the use of infrared spectroscopy independently but in conjunction with other methods to analyze and verify the β-cyclodextrin inclusion compound, which is completely different from the principle and method of the present invention.

Contents of the invention

The object of the present invention is to provide a method for analyzing β-cyclodextrin inclusion compound by Fourier infrared spectroscopy, the analysis method has good reproducibility.

The technical scheme of the present invention is: a method for analyzing β-cyclodextrin inclusion compound by Fourier infrared spectroscopy, which consists of three main parts: analysis principle, analysis method and steps, and result processing. The present invention finds that the infrared absorption intensity of the β-cyclodextrin inclusion complex guest molecule significantly decreases after inclusion, which is called the infrared effect of the package weakening, which is the basis for using FT-IR to analyze the β-cyclodextrin inclusion compound. Qualitative or quantitative analysis and determination of clathrates can be achieved by measuring the infrared spectra of clathrates and unclad complexes and comparing the positions, shapes, and assignments of their absorption peaks, especially by calculating the changes in absorption intensity.

The method consists of the following steps: instrument: Fourier transform infrared spectrometer: parameters: wavelength range: 4000cm ^-1 -450cm ^-1 , resolution: 4cm ^-1 , scanning times: 1 time/second, scanning time: 1 minute. Infrared sample preparation: use a balance to accurately weigh β-cyclodextrin inclusion complex within the range of 1.0-3.0mg, 120.0mg KBr, grind, tablet, and measure infrared; use a balance to accurately weigh the inclusion compound with the same weight For non-inclusion complexes, use the same method as above to measure infrared; take about 2mg of β-cyclodextrin and about 120mg of KBr, grind, press into tablets, and measure infrared; as above, measure infrared of objects. Spectrum processing and data: The original spectrum is normalized by software, automatic baseline correction, automatic smoothing correction processing, and the spectrum is printed; wave number, transmittance or absorbance data are collected through the software. Result processing: absorption peak wave number and shape identification: compare the inclusion compound, whether the absorption peak position and shape of the infrared spectrum of the non-inclusion compound are basically the same; check whether there is an absorption peak different from β-cyclodextrin or guest molecules, In order to qualitatively analyze whether it conforms to the inclusion mechanism, impurities or other non-inclusion reactions, etc.; calculation of absorption peak intensity: select the absorption peak transmittance or absorbance data in the stretching vibration region before and after inclusion of the guest molecule in the data table, press One of the following calculations: the intensity of the non-inclusion complex is set as 100%, and the relative intensity of the corresponding peak of the inclusion compound is: corresponding intensity = [(100-T _package )/(100-T _not )] × 100% (T is transmission value) or: relative intensity = (A _packet /A _not ) × 100% (A is the absorption value). In actual analysis, the working curve of factors affecting inclusion (such as inclusion time, molar ratio, etc.) and absorption intensity can be made, and the best value can be selected as the standard of quantitative analysis.

The advantages of the present invention are: the present invention is simple and fast, clear and intuitive, can qualitatively or quantitatively analyze and determine whether the inclusion has been included, the degree of inclusion, the inclusion mechanism, and a large amount of information. The novel and powerful tool not only has a certain academic value, opens up a new field of infrared research and application, but also has practical application value in scientific research and production.

Description of drawings

Fig. 1 is β-cyclodextrin infrared spectrum and wave number, T% value figure;

Fig. 2 is paeonol infrared spectrum and wave number, T% value figure;

Fig. 3 is the infrared spectrum, wave number and T% value of 1.0mgβ-cyclodextrin and paeonol inclusion complex, 1.0mgβ-cyclodextrin and paeonol non-inclusion complex.

The data in Figure 1 are:

2004-03-27-1.002 3551 4000.00 400.00 11.22 100.40 4.00 %T 1 1.00

REF 4000 99.12 2000 98.67 600

3392.32 22.40 2928.35 63.15 2346.21 98.98 2061.86 97.13 1639.33 75.38

1414.47 62.40 1368.26 64.13 1335.46 64.29 1302.52 71.13 1243.05 73.70

1157.02 25.48 1079.42 21.66 1028.20 11.21 946.86 71.17 888.85 98.29

858.32 87.78 756.47 78.31 707.79 75.31 652.18 80.63 609.52 69.99

578.34 62.56 530.85 78.92

END 22 PEAK(S)FOUND

The data in Figure 2 are:

2004-03-27-2.002 3551 4000.00 400.00 10.06 100.83 4.00 %T 1 1.00

3225.63 92.91 3091.02 83.38 3071.98 84.29 3020.91 77.74 2975.04 72.55

2937.94 76.24 2916.61 78.26 2847.35 78.10 2711.30 86.10 2624.80 87.24

2414.86 94.84 2089.24 97.35 2039.07 95.74 1944.16 97.58 1914.05 93.45

1619.58 15.89 1576.13 32.78 1524.42 70.07 1504.46 39.48 1465.05 50.93

1439.74 50.68 1429.90 54.12 1408.03 67.98 1369.70 15.22 1333.65 33.60

1255.00 10.06 1230.02 42.16 1207.92 17.84 1175.04 70.53 1139.93 20.83

1070.82 46.99 1022.20 37.78 977.04 56.61 949.59 38.60 859.14 42.15

814.23 34.34 736.40 86.82 705.55 69.40 659.95 85.68 589.90 69.17

573.34 40.21 515.35 86.36 459.28 90.67

END 43 PEAK(S)FOUND

The data in Figure 3 are:

Unincluded compound (1:1 mixture by weight) 1.0mg 3551 4000.00 400.00 12.06 100.87 4.00 %T 1 1.00

REF 4000 99.88 2000 99.38 600

3369.57 27.73 3020.96 76.93 2973.88 70.51 2923.84 58.75 2626.08 91.94

2347.03 99.43 2089.25 97.09 2039.61 96.32 1914.42 96.27 1631.06 21.34

1577.42 43.62 1504.82 51.15 1464.86 51.98 1439.67 48.67 1429.42 48.52

1410.18 54.60 1370.18 21.50 1333.86 36.59 1256.13 18.72 1230.50 47.45

1207.70 30.69 1156.53 28.46 1140.03 27.36 1103.11 40.46 1071.23 27.64

1025.17 12.06 977.32 55.53 948.88 49.23 859.34 60.64 813.88 53.28

758.90 77.76 736.06 82.28 705.62 64.72 659.69 77.84 608.66 75.90

589.44 63.86 573.53 47.14 531.81 82.92 515.80 85.23 459.09 95.87

END 40 PEAK(S)FOUND

Inclusion complex 1.0mg 3551 4000.00 400.00 11.47 99.54 4.00 %T 1 1.00

REF 4000 98.68 2000 97.49 600

3391.96 18.91 2927.37 68.75 2049.99 96.58 1639.47 56.55 1507.93 84.23

1409.15 70.95 1371.10 63.25 1333.22 66.63 1301.78 73.87 1274.88 62.26

1255.96 66.33 1204.90 75.68 1155.76 33.01 1078.73 30.77 1029.15 11.47

946.31 76.88 860.15 90.37 757.00 84.57 704.98 77.19 654.53 82.44

608.80 76.89 577.54 71.29 531.33 83.95

END 23 PEAK(S)FOUND

Detailed ways

1. Analysis principle

β-cyclodextrin is a hollow cylindrical compound composed of 7 glucose groups connected by 1, 4 glycosidic bonds. A guest molecule of comparable size.

The guest molecules fill the holes through inclusion, and the holes also produce steric constraints on the guest molecules, hindering their free vibration. According to the principle of infrared spectroscopy, when the molecular vibration is accompanied by the change of the dipole moment, the vibration of the dipole will generate electromagnetic waves, which interact with the incident electromagnetic waves to produce light absorption. The infrared absorption intensity is proportional to the transition probability, which essentially depends on the change of the dipole moment during vibration:

Transition probability ∝|μ _ab | ² Eo ²

In the formula, Eo is the electric field vector of the infrared electromagnetic wave;

μ _ab is the transition dipole moment, which reflects the change of dipole moment during vibration, which is different from the permanent dipole moment μ _o of molecules. Before the inclusion, the guest molecule does not enter the β-cyclodextrin cavity and vibrates freely, so that its transition dipole moment is |μ _ab |. The vibration and bending vibration are weakened, so that the transition dipole moment is |μ′ _ab |, because |μ _ab |＞|μ′ _ab |, then |μ _ab | ² ＞|μ′ _ab | ² , we have:

Transition probability ∝|μ _ab | ² Eo ² ＞Transition probability ′∝|μ′ _ab | ² Eo ²

This formula shows that the infrared spectrum intensity of the inclusion compound guest molecule is less than the corresponding infrared spectrum intensity before inclusion. Because β-cyclodextrin has a hole, the phenomenon that the vibration of the guest molecule entering the hole is hindered by the inclusion action and the infrared absorption intensity is weakened is called "inclusion weakening infrared effect", which reflects the phenomenon that the guest molecule Changes in absorption strength before and after inclusion. Therefore, it can be used as a basis to judge whether inclusion occurs, and qualitatively or quantitatively indicate whether inclusion has occurred and the degree of inclusion. For a well-included β-cyclodextrin inclusion compound, the decrease in the intensity of the extensional vibration absorption peak after inclusion of the guest molecule is measured in the actual analysis between 20% and 80%, most of which are between 50% and 70%. %, some weak peaks may thus disappear.

The absorption peaks in the infrared spectra of inclusion complexes and non-inclusion complexes are all composed of the original peak contributions or interactions between β-cyclodextrin and guest molecules, from which their attribution can be identified. Comparing the infrared spectra of inclusion complexes and non-inclusion complexes, except that the number of peaks is reduced, and the absorption peak intensity of guest molecules is significantly reduced due to the "inclusion weakening infrared effect", the position (wave number) and shape of the corresponding absorption peaks of the two are basically the same , the two graphs are basically the same in appearance. The reason is that the inclusion interaction between β-cyclodextrin and guest molecules is mainly due to the combination of van der Waals force rather than the formation of chemical bonds, so it is impossible to appear the characteristic peaks representing it. If not, in the functional group area of >1300cm ^-1 , there appear in the clathrate spectrum a characteristic peak different from that of β-cyclodextrin or the guest molecular group, which means that impurities have been introduced during the clathrate process or abnormal occurrences have occurred. Inclusion reactions.

2. Analysis methods and steps (taking Fourier infrared spectrometer as an example)

2.1 Instrument

Fourier transform infrared spectrometer: Spectrum One FT-IR Spectrometer, USA, PE company.

2.1.1 Parameters

Range: start 4000cm ^-1 , end 450cm ^-1

Resolution: 4cm ^-1

Scan number: 1/sec

Scan time: 1 minute

2.2 Infrared sample preparation

2.2.1 Use a balance to accurately weigh the β-cyclodextrin inclusion complex within the range of 1.0-3.0mg, 120.0mg KBr, grind, press into tablets, and measure infrared.

2.2.2 Accurately weigh the non-inclusion compound (mixture) with the same weight as the inclusion compound with a balance, measure the infrared in the same way as above.

If necessary, test the following samples:

2.2.3 Take about 2mg of β-cyclodextrin and about 120mg of KBr, grind, press into tablets, and measure infrared.

2.2.4 Same as above, measure object infrared.

2.3 Spectrum processing and data

2.3.1 The original map is processed by "Normalize" (ordinate limit=1.0A), "Baseline correction" (Automatic) and "Smooth" (Automatic) in "process".

2.3.2 Print atlas and "peak table" to collect cm ^-1 and T% data.

2.3.3 or after 2.3.1, select "Absorbance" and set "Threshold=0.0088A" in "parameters", print the spectrum and "peak table" to collect cm ^-1 and A% data.

2.3.4 Coordinate superposition processing of clathrate and non-clathrate spectra.

3. Result processing

3.1 Absorption peak position (wave number), shape identification

Comparing the clathrate, whether the absorption peak position and shape of the infrared spectrum of the non-clathrate are basically the same; check whether there is an absorption peak different from that of the β-cyclodextrin or the guest molecule, so as to qualitatively analyze whether it conforms to the clathrate mechanism, the presence of Impurities or other reactions of non-inclusion interactions, etc.

3.2 Calculation of absorption peak intensity

Select the absorption peak T% or A% (mainly in the stretching vibration region) of the guest molecules before and after inclusion in the "peak table" to calculate according to one of the following formulas:

3.2.1 Set the intensity of the non-inclusion complex as 100%, and the relative intensity of the corresponding peak of the inclusion compound is:

Corresponding intensity = [(100-T _bag )/(100-T _not )]×100% (T is the transmission value)

or

3.2.2 Relative strength = (A _package / A _not ) × 100% (A is the absorption value)

In actual analysis, the working curve of factors affecting inclusion (such as inclusion time, molar ratio, etc.) and absorption intensity can be made, and the best value can be selected as the standard of quantitative analysis.

4. Examples

According to the method of the invention, the inclusion compound and non-inclusion compound of β-cyclodextrin and paeonol are analyzed and measured, and the combined spectrum, data and results are processed as follows:

Based on the above infrared spectra, the following discussion is made:

1) The absorption peaks of the infrared spectrum of the non-inclusion compound are jointly composed of β-cyclodextrin and paeonol. Which belong to β-cyclodextrin: 3392cm ^-1 (covered by 3369.57cm ^-1 broad peak), 2923.84cm ^-1 , 1639.33cm ^-1 (covered by 1631.05cm ^-1 ), 1156.53cm ^-1 , 1025.17cm ^-1 , 948.88cm ^-1 , 608.66cm ^{-1 ,} etc. Attributed to paeonol are: 1619.58cm ^-1 (covered by 1631.05cm ^-1 ), 1504.82cm ^-1 , 1370.18cm ^-1 , 1333.86cm ^-1 , 1256.13cm ^-1 , 1207.70cm ^-1 , 859.34cm ^-1 , 573.53cm ^-1 etc. Infrared spectrum absorption peak of inclusion complex is also composed of β-cyclodextrin and paeonol, which can be checked in detail from the data listed in Figure 1 and Figure 2.

2) Under the condition of the same amount of sample, the intensity of the infrared spectrum absorption peak of the inclusion compound is obviously lower than that of the corresponding peak intensity of the non-inclusion compound. Take 1.0mg sample amount as an example, see Table 1 for details.

Table 1 Comparison table of absorption peak cm ^-1 , T%, and relative intensity of inclusion complex and non-inclusion complex

Relative Strength Relative Strength

cm ^-1 T% *(%) cm ^-1 T% *(%)

Inclusion complex 1639.47 56.55 55.2 1507.93 84.23 32.3

Unincluded 1631.05 21.34 100 1504.82 51.25 100

Inclusion complex 1371.10 63.25 46.8 1333.22 66.63 52.6

Unincluded 1370.18 21.50 100 1333.86 36.59 100

Inclusion complex 1255.96 66.33 41.4 1204.90 75.68 35

Unpacked 1256.13 18.72 100 1207.20 30.69 100

Clathrate 860.15 90.37 24.5

Unincluded 859.34 60.64 100

*: The intensity of the non-inclusion compound is set as 100%, and the relative intensity of the corresponding peak of the inclusion compound is calculated by the following formula:

Corresponding intensity = [(100-T _bag )/(100-T _not )]×100% (T is the transmission value)

3) Comparing the infrared spectra of inclusion compound and non-inclusion compound, the peak shape and wave number are basically the same. In the functional group region with a wave number > 1300cm ^-1 , no new group characteristic peaks appear in the infrared spectrum of the clathrate, indicating that the clathrate between β-cyclodextrin and paeonol does not form a chemical bond, that is, clathrate It is not completed in the form of forming chemical bonds, which conforms to the inclusion mechanism.

Based on the above, the following conclusions can be made:

Comparing the infrared spectra of paeonol inclusion complex and non-inclusion complex (mixture) of β-cyclodextrin, the corresponding peak positions (wave numbers) and shapes are basically the same, and no abnormal peaks are seen, which proves that there is no impurity or non-inclusion reaction , the intensity decreased obviously, indicating inclusion; the absorption strength decreased by 45%-75%, indicating that the inclusion degree was intact.

Claims (4)

1. A method for analyzing β-cyclodextrin inclusion compounds by Fourier infrared spectrometry, characterized in that: the method consists of the following steps: 1. Instrument: Fourier transform infrared spectrometer: parameters: wavelength range: 4000cm ^-1 -450cm ^-1 , resolution: 4cm ^-1 , scanning times: 1 time/second, scanning time: 1 minute; 2. Infrared sample preparation: 2.1 Use a balance to accurately weigh the β-cyclodextrin inclusion compound within the range of 1.0-3.0mg, 120.0mg KBr, grind, tablet, and measure infrared; 2.2 Use a balance to accurately weigh the non-inclusion compound with the same weight as the inclusion compound, and measure the infrared with the same method as above; 2, 3 Take about 2mg β-cyclodextrin, about 120mg KBr, grind, press into tablets, measure infrared; 2, 4 same as above, measure object infrared; 3. Map processing and data: 3.1 Normalize the original spectrum through software, automatic baseline correction, automatic smoothing correction processing, and print the spectrum; 3.2 Collect wavenumber, transmittance or absorbance data through software; 4. Result processing 4.1 Absorption peak wave number and shape identification: Comparing the clathrate, whether the absorption peak position and shape of the infrared spectrum of the non-clathrate are basically the same; check whether there is an absorption peak different from that of the β-cyclodextrin or the guest molecule, so as to qualitatively analyze whether it conforms to the clathrate mechanism, the presence of Impurities or other reactions of non-inclusion interactions, etc.;. 4.2 Calculation of absorption peak intensity: In the data table, select the absorption peak transmittance or absorbance data in the stretching vibration region before and after inclusion of the guest molecule, and calculate according to one of the following formulas: 4.2.1 Set the intensity of the non-inclusion complex as 100%, and the relative intensity of the corresponding peak of the inclusion compound is: Corresponding intensity = [(100-T _bag )/(100-T _not )]×100% (T is the transmission value) 4, 2, 2 relative strength = (A _package / A _not ) × 100% (A is the absorption value) In actual analysis, the working curve of factors affecting inclusion (such as inclusion time, molar ratio, etc.) and absorption intensity can be made, and the best value can be selected as the standard of quantitative analysis.

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