SU1033180A1 - Method of producing modified silica containing adsorbent for liquid cromatography - Google Patents

Abstract

1. MODIFIED METHOD POLUYENIYA KREMNEZEMSODERZHSCHEGO .ADSORBENTA FOR LIQUID CHROMATOGRAPHY, vklyuchnhtsy sing gas passing through silica saturated organosilicon compound when heated from L and h as wk, and also to the fact that, with the purpose e preparing an adsorbent the content of hydroxyl groups and op ganosiloksanovyh With a ratio of 1:10 to 2: 1 to enable the analysis of polar and non-polar substances in both direct and reverse phase variants, the silica is preheated in vacuum at 400-1000 s. after passing the gas, silica evacuates the rf product obtained after evacuating it is treated with water for 2-3 hours. 2, the method according to claim 1, is relative and, in order to increase the degree of saturation with the organosilicon compound, transmission. the gas saturated with the latter is repeatedly carried through the adsorbent layer. | 3. Method according to paragraphs. 1 and 2, for example, and with the aim that, in order to simplify the process, a pair of organosilicon compound 1 is passed through a layer of n-aei-gem.

Description

WITH

The invention relates to the preparation of modified adsorbets and can be used in liquid chromatography. A method for producing modified silica gel by treating it with alkoxyacyloxy or chlorosilanes on subsequent hydrolysis (or preliminary hydrolysis), polymerization and thermal treatment leads to the formation of dehydration of polymer molecules. a different and hard surface of silica gel Cl A disadvantage of the known method is that the resulting adsorbed can be used only in one reverse phase liquid chromatography version. A known method of producing modified silica by means of a silanising reaction is that the silica gel is suspended in toluene, in which dimethylchlorosilane is added, then the suspension is boiled for 10 days without air access. The product is filtered and washed successively with ash, methylene chloride, methanol, methanol-water mixture (1: 1) and dried under vacuum at 180 ° C. Then the product is subjected to additional silanization with hexamethyldisilazane according to the scheme described above. The resulting silanized product is exposed to chlorine and bromine in the ultraviolet, if the reaction with methylrot shows the presence of the remaining unreacted hydroxyls. After demolition, the product is filtered off, diluted with methylene chloride, evacuated at and 5 ml of diethylenetriamine in 60 ml of diamethylformamide are added. This reaction is carried out at 80 ° C. Next, the silica gel is filtered, washed successively with methanol, a methanol-aqueous solution (1: 1 /, water, methanol and dried in vacuum at 140 ° C. 21) However, a large number of side reactions associated with oxidation, hydrolysis and polymerization of silanizing agents, which leads to the formation of a non-uniform surface, requires a large amount of solvent and a long wash-out procedure. In addition, the adsorbent obtained in a known manner can only be used in one embodiment matografii, namely a reverse phase, i.e. for separating substance

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it is distinguished by the ability to non-specific dispersion interaction, for example, members of one homologous series. The closest to the invention, the technical essence and the achieved result is a method of obtaining a modified silica-containing adsorbent for liquid chromatography, including passing a gas saturated with a silicon compound, for example hexamethyldisilazane at a temperature of 200-300 C, followed by purging with pure gas at a temperature of 15 ° C through a layer of silica -20 ° C higher than when passing a gas-vapor mixture H. A disadvantage of the known method is the lack of use of the obtained adsorbent for analysis of polar and non-polar substances both in the forward and in the reverse-phase embodiments. The goal of the invention is to obtain an adsorbent with a content of hydroxyl and organosiloxane groups with a ratio from 1:10 to 2: 1 to enable the analysis of polar and non-polar substances in both direct and reverse phase variants. The goal is achieved according to the method of obtaining a modified silica-containing adsorbent for liquid chromatography, including passing a gas saturated with silicon-organic compound through a layer of silica upon heating, preheating the silica in vacuum at 400-1000 s followed by evacuating the silica after passing the gas and processing the product for 1000 to 1000 sec. within 2-3 hours. For the purpose of increasing the degree of saturation with the organosilicon compound, the passage of the gas saturated with the latter through a layer of silica is repeatedly carried out. In addition, in order to simplify the technology, a vapor of the organosilicon compound is passed through the layer of silica. The technology of the method consists in the fact that the silica is first evacuated at 400-1000 ° C to create the desired concentration of reactive surface hydroxyls, i.e. partial dehydroxy or {yuvanie:

Then the sample is modified three times with silanizing agents, “for example, in pairs of trimethylchlorosilane, triethyl chlorosilane, hexamethyldisy§bO-ii-0-k-J o-ji-o-i-0- $ i I-BX. 0

0R -. CHj; 02% R-.CHjiC HylC HslC Hs

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The sample is then pumped out at 200 ° C to remove the reaction products and

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after which the sample is dried to a constant weight. In a way, an adsorbent blends on the surface a predetermined ratio of organosiloxane and hydroxyl groups, determined mainly by the temperature and the time of the preliminary evacuation. The hydroxyl groups determine the separation of polar substances in the classic version, and the alkylsiloxane groups provide the separation of substances in the reverse phase liquid chromatography version.

Example 1. A 300 cm silica gel C-3 (with a specific surface of 265) with a part size of 10-15 µm is loaded into a pulp and pumped out for 50 hours to a residual pressure of 10 5-10-bmm Hg. Then into a cooled flask About 1 cm of trimethylchlorosnlan is refrozen, the tekteratura is raised to 400 s and maintained at it for 3 h. Then the adsorbent is pumped out from the reaction products to mm Hg, st. and repeat the modification under the conditions described 2 more times. By a three-fold modification, the complete silanization of 99.9% is achieved. The ampoule evacuated from the reaction products is frosted with 1 cm of water, the temperature is raised to 100 C and kept at this temperature for 3 hours. As a result of this method, a silica adsorbent is obtained with a ratio of hydroxyl and grafted organosiloxane groups of 1: 4.

lasane, dimethylallychlorosilane or dimethylphenylchlorosilane at 100-40СгС | in vacuum (to exclude access of air and moisture):

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rehydroxylated with water at 100 ° C in the course of 2-3 hours:

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The amount of residual hydroxyl groups and grafted organosiloxane groups is determined by the difference in concentration of the starting and orthotic hydroxyl groups. The number of hydroxyl groups is determined from triethylamine adsorption isotherms.

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By varying the temperature of pre-pumping of the starting silicas in the range of 400–1000 ° C, the ratio of hydroxyl and grafted organosiloxane groups on the surface in the range from 1:10 to 2: 1 is obtained. This interval of the ratios of polar and under-sized groups on the surface of silica is optimal for using the adsorbent in both versions of liquid chromatography.

Example 2a On a 10 x 0.4 cm column with the obtained silica adsorbent, in the classic version (eluent n-hexane, -0 1.5 ml / min), the mixture was separated: benN ol-benzonitrile-annlin with a relative selectivity (oC) for the separation of two latest ct 4,2.

Example 26. At the same column with the same adsorbent at 50 ° C in a reversed-phase version (eluent: 25% isopropyl alcohol and 75% scream, 0.75 ml / min) are separated by ether benzoic acid. Relative to the selectivity of the separation of the adjacent homologues of methyl and ethyl benzoic acid esters ≤ 1.6.

For other known silica adsorbents, only one of the two analyzes given in the example is possible.

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Thus, the use of the predispositions of which, after being silanized by a method of obtaining a modifying and subsequent regenerated silica adsorbent on xylation, creates a certain amount

compared to existing methods, the ratio of hydroxyl and organo-allows to obtain universal siloxane groups, which allows

silica adsorbents working 5 use one and. ty same column

both in classical and in the analysis of both polar and

schenno-phasic variants, on top of non-polar substances.

Claims (3)

1. A METHOD FOR PRODUCING A MODIFIED SILICON-CONTAINING. ADSORBENT FOR LIQUID CHROMATOGRAPHY, including passing through a silica jelly a gas saturated with an organosilicon compound when heated, and eliminating the need for an organic compound to obtain adsorbents groups with relation Niemi * ¹ Is from 10 to 2: 1 in order to allow the analysis of polar and non-polar substances in both forward and in reverse-phase embodiments, the silica is preheated in vacuum at 400-1000 ° C, propyl .posle -. gas digestion silica ^g evacuate if the resulting product after evacuation is treated with water for 2-3 hours 2, The method of π. 1, it is important that, in order to increase the degree of saturation of the organosilicon compound, the transmission of the gas saturated with the latter through the adsorbent layer is carried out repeatedly. 3. The method according to PP. 1 and 2, distinguished by the fact that, in order to simplify the process, a pair of organosilicon compounds are passed through a layer of siliceous earth. SIJ1033180>