RU172015U1 - CHROMATOGRAPHIC CAPILLARY COLUMN - Google Patents

Abstract

The utility model relates to capillary gas chromatography, namely to open-type capillary columns, and can be used both for the analysis of complex multicomponent mixtures of organic compounds and for working with a mass spectrometer. An open type chromatographic capillary column is described, consisting of a capillary, on the inner surface of which a layer of a stationary liquid phase is applied uniformly along the length of the column, while the layer of a stationary liquid phase is a polymer consisting of silarylene and diphenyl-polysiloxane blocks. EFFECT: high selectivity. 6 c.p. f-ly, 2 ave., 4 ill.

Description

The utility model relates to capillary gas chromatography, namely to open-type capillary columns, and can be used both for the analysis of complex multicomponent mixtures of organic compounds and for working with a mass spectrometer.

Known capillary columns, including a quartz capillary, containing a layer of a stationary liquid phase (NLC) inside the capillary [US No. 4293415, B01D 15/08, G01N 30/60, 10/06/1981; B.A. Rudenko, G.I. Rudenko, Highly efficient chromatographic processes, Moscow, Nauka, 2003, v. 1, pp. 115-145]. The most common NLFs at the moment are polysiloxane polymers. However, the polysiloxane polymers (Fig. 1A) have a decay mechanism due to the significant mobility of the polysiloxane skeleton [Kharitonov NP, Ostrovsky VV, - L .: Nauka, 1982. - 208 pp.], Which limits the use of polysiloxane NSFs for temperature over 300 ° С.

An increase in the maximum allowable working temperature for a capillary column with polysiloxane NSF is achieved by reducing the mobility of the polysiloxane skeleton. From the available data it follows that the flexibility of the polysiloxane skeleton is reduced in the presence of cross-linking of the polymer with each other, as well as as a result of the replacement of some of the oxygen atoms of the polysiloxane skeleton with rigid bulk structures [Blomberg L.G., Markides K.E. JHRCCC. - 1985. - V. 8. N. 10 - R. 632-650].

This task can be achieved in several ways. The most famous are the incorporation into the polysiloxane skeleton of rigid inserts such as n-phenylene (silarylene) (Fig. 1D) [Dunnawant W.R. Inorg. Macromol. Rev. - V. 1, N. 9, - P. 165-189], n-phenylene oxide (Fig. 1B) or carboran (Fig. 1C) [Shroeder N.A. Inorg. Macromol. Rev - 1970 - V. 1, N. 1 - P. 45-73]. Thus, the silarylene phase consists of polysiloxane blocks separated by silarylene blocks (Fig. 1D).

It is also possible to use sol-gel technology for binding polysiloxane chains to each other [US No. 8685240, B01D 15/08, 01/01/2014].

However, some of these methods of increasing thermal stability have disadvantages. Thus, the use of sol-gel technology for crosslinking polysiloxane molecules can lead to the formation of an excessive amount of crosslinking, which can capture a significant part of the polymer. As a result, it becomes sterically impossible to deactivate the remaining silanol groups. In addition, in an excessively crosslinked phase, the diffusion coefficient decreases and it becomes unsuitable for chromatographic separation [Hoffamn S., Blomberg L. G, Buijten J. - J. Cromatogr - 1984 - V. 302 - P. 95-106.].

As for carborane-based NLC, despite the good quality of hydrocarbon separation and high thermal stability, this phase does not allow the separation of alcohols and primary amines, which is associated with the presence of boron in the phase, and this inhibits the use of this phase in gas chromatography [Dames P., Cumbers M. - International Laboratory. - 1989 - N. 7 - P. 376].

Currently, the most successful are the columns based on the dimethylsilarylene phase (Fig. 1D) [Bemgard, Blomberg JC&CC 1987, V. 10], and methylphenylsilarylene phase (J. Buijten .. J of Chromatogr., 301 (1984)), (Fig. . 1E.) Both of these phases have high thermal stability and differ in polarity, which provides different selectivity for the separation of mixtures of compounds of different chemical classes. However, these phases have low chromatographic polarity values, which does not guarantee separation of an arbitrary mixture of polar compounds.

The technical problem is to develop an effective thermostable chromatographic open type capillary column.

EFFECT: high selectivity, different from that which is known for columns with dimethylsarylene (DMS) and methylphenylsilarylene (MPS) phases.

The technical result is achieved through the use of an open-type chromatographic capillary column consisting of a capillary, on the inner surface of which a layer of a stationary liquid phase is applied uniformly along the length of the column, while the layer of a stationary liquid phase is a polymer consisting of silarylene and diphenyl polysiloxane blocks.

The content of silarylene blocks in the polymer is 48-50%, and diphenylsiloxane 50-52%.

The polymer does not contain hydroxyl groups.

Diphenylpolysiloxane blocks contain substituents in one or two phenyl nuclei belonging to the side substituents of the polymer or phenyl nucleus of the silarylene group.

Substituents on the phenyl nuclei may be a methyl group, fluorine, fluoromethyl, difluoromethyl, trifluoromethyl or cyano groups.

The capillary material is metal or glass, or fused silica with an external coating of aluminum or polyimide.

Currently, silarylene-based polymers have been proposed to change the selectivity of silarylene phases, where polar inserts based on cyanopropylsiloxane are used instead of dimethyl and methylphenyl polysiloxane units. These are BPX 90 (SGE) type phases. However, these phases do not have sufficient thermal stability; their maximum operating temperature is 280 ° C. Accordingly, these phases are not a solution to the problem of changing the selectivity of thermostable phases based on polysiloxane-silarylene.

The problem is solved in that in an open-type chromatographic capillary column consisting of a capillary, an NJP film is applied uniformly along the length of the column along the column surface, which is a polymer with a structure containing diphenylpolysiloxane and silarylene blocks (Fig. 1F)

The inventive column contains, as an NLC, a polymer containing silarylene fragments, the content of which is in the region of 48% by the number of these fragments in the polymer chain, performs the function of decreasing the mobility of the polysiloxane chain, and the diphenylpolysiloxane fragment (approximately 52% of it) changes the order of the substances leaving the column according to in comparison with columns using LCFs based on VHI and MFS. Thus, this polymer used to prepare a capillary column contains only diphenylsiloxane and silarylene blocks. A further change in the selectivity of the columns is possible by using substituents in the lateral phenyl groups (Fig. 1G), such as methyl, fluorine, trifluoromethyl, nitrile group. This choice of substituents is based on the fact that these groups in the benzene core change the dipole moment of the polymer fragment and do not violate the thermal stability of the polymer.

The introduction of functional groups into the aromatic ring of the silarylene block will have a similar effect on selectivity (Fig. 1K).

The closest structure to DFS NJF Optima 35 company Macherey-Nagel (Fig. 1H). This phase contains 65% dimethylsiloxane fragments and has selectivity such as dimethylpolisioxane phases containing methyl and phenyl phases in the polysiloxane chain [Macherey-Nagel, 2015 Gas Chromatography. Application Guide / Technical Handbook]. Thus, in terms of selectivity, this phase is close to such phases as: DB-36, HP-35, BPX-35, OV-11.

The material of the capillary, which was applied to the application of NLF based on DFS, is quartz with a polyimide and aluminum coating, glass, and metal. For applying DFS and phases based on DFS on the capillary wall, the static method of both low and high pressure is used. Before application, the capillary is treated with a disilazane-based reagent (1,3-divinyl-1,3-dimethyl-1,3-diphenyldisilazane) at a temperature of 350 ° C. Then the column is washed with solvents from the reaction products. Next, the phase is applied by the static low-pressure method [B.A. Rudenko, G.I. Rudenko, Highly efficient chromatographic processes, Moscow, Nauka, 2003, v. 1, pp. 115-145].

The technical effect of the invention is to achieve a specific column efficiency of up to 3500-3700 theory. plates per meter and the ability to work at temperatures up to 360 ° C without impairing its effectiveness and with low background currents. This circumstance makes it possible to work with high-boiling compounds having boiling points up to 500 ° C and allows the separation of substances whose separation on the columns with VHI and MPS is difficult.

The thermal stability of the claimed column is illustrated in FIG. 2, which shows the background current level of columns with NLC on the basis of DMS, MFS, DFS and a column with polysiloxane OV-1, depending on the temperature of the column. It can be seen that all columns with silarylene blocks have a lower background current level at a temperature of 350 ° C compared to polysiloxane NJF. To obtain this dependence, the columns with a length of 20 meters were alternately installed in the thermostat of the chromatograph and the thermostat temperature was programmed according to the following program: 250 ° C (5 min) - 350 ° C (5 ° C / min). GN: helium, evaporator: T = 350 ° C, detector: mass spectrometer.

The invention is illustrated by the following examples and illustrations.

FIG. 1 describes the starting polysiloxane polymer (FIG. 1A) and possible structures of thermostable modified polysiloxanes (FIG. 1B-K). Of which: FIG. 1F, FIG. 1G and FIG. 1K describe the structures proposed in the work.

FIG. Figure 2 describes a comparison of the thermal stability of an unmodified polysiloxane column (curve 1), compared with polydiphenylsiloxanesilarylene (curve 2), polydimethylsiloxane silarylene (curve 3) and polymethylphenylsiloxanesilarylene (curve 4).

FIG. 3 is an example of a separation chromatogram of a high boiling mixture of sterols and tocopherols on a column with a thermostable methylphenylsilarylene phase. Analysis conditions: Temperature program: 250-350 ° C (4 ° C / min), carrier gas: helium, evaporator: t = 350 ° C, detector: mass spectrometer. Column 20 m * 0.25 mm * 0.3 μm. Peak designations: a - β-Tocopherol, b - α-Tocopherol (vitamin E), c - Campesterol, d - Stigmasterol, d - β-Sitosterol, e - Cholest-7-enol (Δ ⁷ -sterol).

FIG. 4 is an example of the separation of a complex test mixture of normal hydrocarbons and oxygen-containing compounds on different columns with silarylene phases: A - polydimethylprisiloxanesilarylene, B - polymethylphenylsiloxanesilarylene, C - polydiphenylsiloxanesilarylene. The peak designations in FIG. 4 are as follows: 1 - butanone-2, 2 - butanal, 5 - pentanon-2, 6 - pentanal, 9 - hexanal, 12-heptanon-2, 13 - hexanal, 16 - octanon-2, 17 - octanal, 20 - nonanone -2, 21 - nonanal. Alcohols-1: 4 - butanol, 8 - pentanol, 11 - hexanol, 15 - heptanol, 19 - octanol, 23 - nonanol, 25 - decanol, 27 - undecanol. Hydrocarbons: 3 - heptane, 7 - octane, 10 - nonane, 14 - decane, 18 - undecane, 22 - dodecane, 24 - tridecane, 26 - tetradecane.

Example 1

An example of thermal stability for a column with a LCA phase is the separation of plant sterols (Fig. 3). For separation, a column of 20 m and an inner diameter of 0.25 mm is used, inside which a layer of diphenylsiloxanesilarylenic polymer (DPS) is created. Non-derivatized sterols are separated from milk thistle oil. The column temperature is 250 ° C-350 ° C with a temperature programming rate of 4 ° C / min. At the outlet of the column, a mass spectrometer was installed. It can be seen that a good separation of high-boiling components was achieved, and the absence of a mass spectrometric background made it possible to identify these components.

This example allows us to see that, firstly, the column does not lose its separation properties at 350 ° C and has a selectivity sufficient to separate a complex mixture of high boiling organic compounds.

Example 2

In FIG. 4 shows the separation of a mixture of carbonyl compounds, alcohols and carbohydrates for columns with different selectivities. Columns with the LCF DMS, MFS and DFS were studied in the separation of classes of compounds such as alcohols, hydrocarbons and carbonyl compounds.

This example shows the capabilities of the claimed column for the separation of various classes of chemical compounds. On the obtained chromatograms, it can be observed that in the case of the LCA phase, the retention times of the alcohols completely coincide with the retention times of the hydrocarbons and, as a result, they appear in the chromatogram with one peak. In the case of the DPS column, the retention times coincide for some carbonyl compounds and hydrocarbons because carbonyl compounds are retained even more relative to hydrocarbons due to the polarity of the NLC. Thus, the most complete picture of the separation is observed on the MFS column, where all peaks are separated. This situation is an example of the fact that to solve a specific task, the correct choice of column is necessary for the best separation of the mixture. That is why it is important for practical work to have a number of columns of different selectivity in order to cover the maximum number of potential chromatography tasks.

Claims (7)

1. An open-type chromatographic capillary column, consisting of a capillary, on the inner surface of which a layer of a stationary liquid phase is applied uniformly along the length of the column, characterized in that the stationary liquid phase layer is a polymer consisting of silarylene and diphenyl polysiloxane blocks. 2. The chromatographic capillary column according to claim 1, characterized in that the content of silarylene blocks in the polymer is 48-50%, and diphenylsiloxane 50-52%. 3. Chromatographic capillary column according to claim 1, characterized in that the polymer does not contain hydroxyl groups. 4. The chromatographic capillary column according to claim 1, characterized in that the diphenylpolysiloxane blocks contain substituents in one or two phenyl nuclei belonging to the side substituents of the polymer. 5. The chromatographic capillary column according to claim 4, characterized in that the substituents in the phenyl nuclei can be a methyl group, fluorine, fluoromethyl, difluoromethyl, trifluoromethyl or cyano groups. 6. Chromatographic capillary column according to claim 5, characterized in that the substituents are contained in the phenyl core of the silarylene block. 7. The chromatographic capillary column according to claim 1, characterized in that the capillary material is metal or glass, or fused silica with an external coating of aluminum or polyimide.

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