RU2548360C2 - Method of quantitative determination of methane-fullerenes in reaction mix by uv-spectroscopy method - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to the method of quantitative determination of methane- fullerene of various level of replacement in reaction mix using UV-spectroscopy method consisting in reading of UV-spectra, plotting of calibration curves using the values of the second derivative of the spectrum, finding from them of the linear regression equations. Meanwhile for preparation of models of the studied compounds with various levels of replacement the organic solvents are used, UV-spectra are recorded in a wide interval of concentration, the linear regression equations for determination of the content of mono-replaced methane- fullerenes h=1.23×10^-4c+0.01×10^-5, di-replaced h=1.54×10^-4c+0.20×10^-5, three-replaced h=2.31×10^-4c+0.30×10^-5 tetra-replaced h=4.00×10^-4c+0.32×10^-5 then when determining methane-fullerenes with various levels of replacement in a reaction mix the analysed samples are selected from the reaction mix, UV-spectra are read, the curves are plotted on the basis of values of the second derivative of the spectrum, the respective value h is substituted in the respective linear regression equation and the concentration of methane-fullerenes in the analysed mix is calculated.

EFFECT: present invention allows to determine quantitatively the composition of complex reaction mixes of isomeric compounds consisting of two and more components in a wide range of concentration without their separation from a reaction mix with a possibility of the subsequent performing of the process before pre-planned ratio of ingredients.

2 cl, 5 tbl, 8 ex, 2 dwg

Description

The invention relates to methods for the quantitative determination of complex reaction mixtures, in particular methanofullerenes of various degrees of substitution by UV spectroscopy. The invention can also find application in studying the structure of fullerene-containing macromolecular compounds, where all possible types of C ₆₀ incorporation into the polymer chain (star-shaped, fullerene in the main chain, fullerene at the ends of the macromolecule, etc.) are most correctly established on the basis of UV spectra.

A known method for the quantitative determination of an industrial mixture for the production of m-cresol containing o-, n-isomers of cresols, 2,4-, 2,5-, 2,6-xylenols and o-ethylphenol (GB patent 760729 from 16.12.1953) . The IR and UV spectra were recorded in the gas phase at 200 ° C, and only m-cresol was determined in the mixture with an accuracy of 0.3-3.0%, and the percentage error of the device in this method is 2%. This technique allows with sufficient accuracy to determine the content of only one component in the mixture, and it is unsuitable for the analysis of several compounds. In addition, the recording of UV spectra in the gas phase is very difficult due to the fact that not all organic substances can be converted into the gas phase without decomposition.

Closest to the proposed invention is a method for determining the amount of cefoperazone and sulbactam in a mixture, which consists in taking UV spectra, graphically finding the first and second derivative of the spectra (Journal of Pharmaceuticul & Biomedicul Analysis, 1994, V.12, No. 5. P.653- 657). However, in the indicated method, the spectra are recorded only in water, and this significantly narrows the range of the analyzed compounds, which dissolve exclusively in polar and nonpolar organic solvents. By the specified method, it is possible to measure the concentration of only two compounds that are purchased at the factory, and the authors only prepare solutions of various concentrations.

The aim of the invention is to develop a method for the quantitative determination of the composition of complex reaction mixtures of isomeric compounds consisting of two or more components in a wide range of concentrations without isolating them from the reaction mixture with the possibility of the subsequent process to a predetermined ratio of ingredients.

This goal is achieved in that the determination of the composition of complex reaction mixtures is carried out in two stages. At the first stage, the UV spectra of the isolated methanofullerenes differing in the type and number of substituents are removed and processed. Based on the second derivative of the UV spectra, calibration graphs are constructed, according to which the linear regression equations are determined. At the second stage, methanofullerenes of various degrees of substitution are synthesized, their spectra are taken, and the quantities of substituted methanofullerenes are determined from the linear regression equations found at the first stage corresponding to the type of substitution.

The first stage is implemented as follows. Five complex mixtures of methanofullerenes, differing in the number of substituents in the C ₆₀ core, were initially synthesized. Mixtures on a chromatographic column were divided into components depending on the number of substituents in fullerene, i.e. individual compounds were isolated. Then, solutions were prepared in organic solvents (chlorinated benzenes, chlorinated hydrocarbons, toluene, acetonitrile): arbitrarily selected 5 or 6 concentration values in the range of 10 ^-4 -10 ^-6 mol / l (the indicated interval is advisable, since for large than 10 ^{- 4} mol / L concentrations, the height of the characteristic peaks is higher than the optical absorption scale, and at concentrations less than 10 ^-6 mol / L, the height of the characteristic peaks is at the level of measurement error of the spectrophotometer), with each of the methanofullerenes. The UV spectra of all samples were recorded. The spectra were recorded at room temperature in the wavelength range from 190 to 1100 nm, however, the most characteristic range is 250-400 nm, a slit width of 2.0 nm, using a quartz cuvette 1 cm thick. Since the absorption spectra of a mixture of methanofullerenes of various degrees of substitution consist of a number of overlapping bands, the determination of the number of derivatives of methanofullerenes is an intractable task. The highest selectivity of spectrophotometric analysis is achieved by passing to the second derivatives of UV spectra, i.e. in the study of concentration dependences d ² A / dλ ² = f (λ). Testing of various Δλ values revealed that a step-by-step coefficient Δλ = 40 shows the best selectivity, high sensitivity and an adequate signal-to-noise ratio for experimental work.

The dependences d ² A / dλ ² -f (λ) (Fig. 1) measured the corresponding h ₁ (monosubstituted methanofullerenes), h ₂ (disubstituted), etc. the amplitudes between the minimum and maximum d ² A / dλ ² at all concentrations, which were then used to construct the calibration graph (Fig. 2). Based on the calibration graph of the concentration of mono-, di-, etc. of the substituted methanofullerene from the second derivative, the linear regression coefficients needed to calculate the molar concentrations of methanofullerenes were found. The linear regression parameters for the concentration dependences of the optical density and d ² A / dλ ^{2 are} presented in table 1.

Table 1 Parameters of linear regression for concentration dependences d ² A / dλ ² Adduct λ, nm Linear equation R S _r × 10 ³

regression mono- 359/329 h = 1.23 × 10 ^-4 s + 0.01 × 10 ^-5 0.9993 1.7 di- 347/320 h = 1.54 × 10 ^-4 s + 0.20 × 10 ^-5 0.9993 3.3 three- 334/308 h = 2.31 × 10 ^-4 s + 0.30 × 10 ^-5 0.9997 0.6 tetra 317/279 h = 4.00 × 10 ^-4 s + 0.32 × 10 ^-5 0.9976 1.5

The second stage is implemented on specific examples of the method for the quantitative determination of methanofullerenes in the reaction mixture in various solvents.

Example 1. To a solution of 0.1 g (0.14 mmol) of fullerene C ₆₀ in 30 ml of toluene was added 0.069 g (0.2 mmol) of CBr ₄ , 0.033 ml (0.18 mmol) of diallyl malonic acid ester and 0.32 ml (0.21 mmol) of diazabicyclo [4.2.0 ] undec-7-ena (DBU). The reaction mass was stirred in an inert atmosphere at room temperature for 1.5 hours, then filtered, the filtrate was washed with 5% HCl, dried over MgSO ₄ , and evaporated. The residue was separated by column chromatography on SiO ₂ , the eluent was toluene. Received 0.040 g (~ 32 wt.%) Monosubstituted, 0.02 g (~ 14%) disubstituted, 0.015 g (~ 8%) trisubstituted and 0.01 g (~ 5%) tetrasubstituted products. Spectroscopic analysis of the reaction mixture showed (35.2 wt.%) Monosubstituted, (15.9%) disubstituted, (8.8%) trisubstituted and (6.3%) tetrasubstituted products.

Example 2. Analogously to example 1, only the process time is 4 hours. After separation by column chromatography on SiO ₂ (toluene), we obtained: (12 wt.%) Monosubstituted, (36%) disubstituted, 0.015 g (24%) of trisubstituted and (15%) tetrasubstituted products. Spectroscopic analysis of the reaction mixture showed (14.3 wt.%) Monosubstituted, (37.0%) disubstituted, (25.8%) trisubstituted and (18.2%) tetrasubstituted products (Table 2). To evaluate the results of the quantitative analysis of methanofullerene mixtures, they were compared with HPLC data (chromatographic conditions: Shimadzu LC-20 chromatographic system with a spectrophotometric diode detector (Japan); detection was performed at a wavelength of 280 nm, an Exsil Silica 250 × 4 column was used, 6 mm, 5 μm, an eluent of the composition hexane: toluene: isopropyl alcohol = 97: 2: 1 was used as the mobile phase, the feed rate of the mobile phase was 1 ml / min.

table 2 Comparison of methods for the quantitative determination of a mixture of methanofullerenes in toluene Number of Deputies Example 1 (1.5 hours) Example 2 (4 hours) Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% mono- 32,0 35,2 35,2 12.0 14,4 14.3 di- 14.0 15.8 15.9 36.0 37.1 37.0 three- 8.0 8.8 8.8 24.0 25.8 25.8 tetra 5,0 6.4 6.3 15.0 18,4 18.2

Example 3. Analogously to example 1, but as a solvent used chloroform (chlorinated hydrocarbon), the process time is 1.5 hours. The results of the analysis of the reaction mixture are presented in table.3.

Example 4. Analogously to example 1, but as a solvent used chloroform (chlorinated hydrocarbon), the process time is 4 hours. The results of the analysis of the reaction mixture are presented in table.3.

Table 3 Comparison of methods for the quantitative determination of a mixture of methanofullerenes in chloroform amount Example 3 (1.5 hours) Example 4 (4 hours)

deputies Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% mono- 34.0 35.8 35.9 16,0 16.5 16.7 di- 10.0 13,2 13,2 40.1 40.8 40.8 three- 8.5 9.0 9.0 26.0 27.5 27.4

Example 5. Analogously to example 1, but acetonitrile was used as a solvent, the process time was 1.5 hours. The results of the analysis of the reaction mixture are presented in table.4.

Example 6. Analogously to example 1, but acetonitrile was used as a solvent, the process time was 4 hours. The results of the analysis of the reaction mixture are presented in table.4.

Table 4 Comparison of methods for the quantitative determination of a mixture of methanofullerenes in acetonitrile Number of Deputies Example 5 (1.5 hours) Example 6 (4 hours) Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% mono- 32.9 35.0 34.9 15.7 17.8 17.9 di- 13,4 14.9 14.9 39.9 41.2 41.2

Example 7. Analogously to example 1, but o-dichlorobenzene (chlorinated benzene) (chlorinated benzene) was used as a solvent, the process time was 1.5 hours. The results of the analysis of the reaction mixture are presented in table.5.

Example 8. Analogously to example 1, but as a solvent used o-dichlorobenzene (chlorinated benzene), the process time is 4 hours. The results of the analysis of the reaction mixture are presented in table.5.

Table 5 Comparison of methods for the quantitative determination of a mixture of methanofullerenes in o-dichlorobenzene Number of Deputies Example 7 (1.5 hours) Example 8 (4 hours) Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% Column chromatography on SiO ₂ , wt.% HPLC, wt.% UV spectroscopy, wt.% mono- 34.3 36.5 36.7 15.9 17.0 17.1 di- 14.1 15.1 15,2 38.6 39.2 39.1

The accuracy of the quantitative determination of the content of various methanofullerenes in the mixture by UV spectroscopy and HPLC is well correlated and comparable. However, in the case of HPLC, the selection of a mixture of eluents for the separation of methanofullerenes is very laborious and the implementation of the method requires very expensive equipment.

Thus, the quantitative determination of various methanofullerenes in complex mixtures by UV spectroscopy makes it possible to establish the concentration of two or more components with high accuracy and in a short time without interrupting the process. Using UV spectroscopy, you can: a) study the kinetics of the reaction of the formation of methanofullerenes based on C ₆₀ ; b) bring the reaction to the planned concentration of the desired isomer in the reaction mixture, i.e. generally control the process.

Claims (2)

1. A method for the quantitative determination of methanofullerenes of various degrees of substitution in the reaction mixture by UV spectroscopy, which consists in taking UV spectra, constructing calibration graphs based on the values of the second derivative of the spectrum, finding linear regression equations from them, characterized in that for preparing samples of the studied compounds organic solvents are used with various degrees of substitution; UV spectra are recorded in a wide range of concentrations; linear regression equations for determining the content of monosubstituted methanofullerenes h = 1.23 × 10 ^-4 s + 0.01 × 10 ^-5 , disubstituted h = 1.54 × 10 ^-4 s + 0.20 × 10 ^-5 , trisubstituted h = 2.31 × 10 ^-4 s + 0.30 × 10 ^-5 , tetrasubstituted h = 4.00 × 10 ^-4 c + 0.32 × 10 ^-5 , then, when determining methanofullerenes of various degrees of substitution in the reaction mixture, the analyzed samples are taken from the reaction mixture , taking UV spectra, plotting based on the values of the second derivative of the spectrum, substituting the corresponding value of h in the corresponding linear regression equation and calculating the concentration of methanofulerenes in aliziruemy mixture. 2. A method for the quantitative determination of methanofullerenes of various degrees of substitution in the reaction mixture by UV spectroscopy according to claim 1, characterized in that chlorinated benzenes, chlorinated hydrocarbons, toluene, acetonitrile are used as organic solvents, UV spectra are recorded in the concentration range 10 ^{- 4} -10 ^-6 mol / l, while the determined amount of components in the mixture is two or more.

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