JPH04212058A - Manufacture of filling agent for liquid chromatography - Google Patents

Abstract

PURPOSE:To enable a filling agent for a liquid chromatography with less remaining silanol groups. CONSTITUTION:A title item is provided with a process for performing chemical connection of an above chemical decoration agent to a silanol group on silica gel or a porous glass surface by allowing the chemical modification agent such as octadecylchlorosilane to react with the silica gel or the porous glass and a process for performing chemical connection of an above end cap to a remaining silane group on the silica gel or the porous glass surface by allowing the end cap agent to react with this chemically modified silica gel or the porous glass at a reaction temperature of 250 deg.C or higher within a vapor.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing a packing material for liquid chromatography in which chemically modified groups such as alkyl groups are introduced into silica gel or porous glass. The present invention relates to a method for producing an inert filler.

0002

[Prior art and problems to be solved by the invention] Conventionally,
BACKGROUND ART As a packing material for high performance liquid chromatography, silica gel is silylated with a silane compound having various chemically modifying groups, so that a chemically modifying group is chemically bonded to a silanol group on the surface of the silica gel. Among these, octadecyl silica gel filler (ODS), in which octadecyl groups are introduced onto the silica gel surface using an octadecylchlorosilane compound, is widely used. Further, as other chemically modified groups, octyl group, butyl group, methyl group, cyanopropyl group, phenyl group, etc. are known.

[0003] In this case, the chemically bonded silica gel packing material described above is used when performing high performance liquid chromatography.
The influence of residual silanol groups present on the silica gel surface of the base material has become a problem. In other words, polar solutes, especially basic solutes, strongly interact with residual silanol groups, and as a result, basic solutes may not elute or their elution may be delayed, peak tailing may occur, and chromatograms with good reproducibility may not be obtained. There are problems such as not being able to get it.

On the other hand, as a means to reduce the influence of the remaining unreacted silanol groups, silica gel to which chemically modified groups have been bonded is again silylated with trimethylchlorosilane or the like, and short-chain alkyl groups are chemically bonded to the remaining silanol groups. End capping is being performed.

[0005] In this case, conventional end capping is
This is carried out by secondary silylation of silica gel in a solvent such as toluene, but even after this endcapping, a considerable amount of silanol groups remain, causing peak tailing.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for producing a packing material for liquid chromatography, which employs a novel end-capping method and is extremely unaffected by residual silanol groups.

[0007]

[Means and Effects for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have discovered that, when endcapping is performed, the reaction is not carried out in a solvent as in the past, but in a gas phase. The present inventors discovered that, surprisingly, it was possible to synthesize a filler with very little influence from residual silanol groups by reacting silica gel or porous glass with an end-capping agent at a temperature of 250°C or higher, leading to the present invention. Ta.

Therefore, the present invention comprises a step of reacting a chemical modifier with silica gel or porous glass to chemically bond the chemical modifier to the silanol groups on the surface of the silica gel or porous glass (hereinafter referred to as the first step); A step of chemically bonding the end capping agent to the residual silanol groups on the surface of the silica gel or porous glass by reacting the chemically modified silica gel or porous glass with an end capping agent at a reaction temperature of 250°C or higher in the gas phase (hereinafter referred to as step 1). (referred to as 2 steps)
Provided is a method for producing a packing material for liquid chromatography, comprising:

[0009] To explain the present invention in more detail below, in the present invention, in the first step, silanol on the surface of silica gel or porous glass is reacted with a chemical modifier having a chemical modifying group. The chemically modified group is chemically bonded to the group.

In this case, the properties of the silica gel used in the first step are not particularly limited, but the particle size is 1 to 1000 μm,
More preferably 2 to 50 μm, pore diameter 0 to 10,000 Å
, more preferably 60-1000 Å, specific surface area 1-10
00 m2/g, more preferably 10 to 600 m2/g can be suitably used. Note that silica gel having a pore diameter of 0 Å, that is, one having substantially no pores may also be used.

[0011] As the porous glass, any of those conventionally used as packing materials for liquid chromatography can be used.
m, more preferably 2 to 50 μm, pore size 0 to 1000
0 Å, more preferably 60-1000 Å, specific surface area 1-
1000m2/g, more preferably 10-600m2/
g can be suitably used. Note that the porous glass contains 80 to 99% by weight of SiO, with the remaining main component being N.
One or more of a2O, B2O3, and Al2O3 may be used.

As the chemical modifier, those conventionally used can be used. Examples include octadecyl group, octyl group, n-butyl group, etc. having 1 to 50 carbon atoms.
, more preferably an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 50 carbon atoms, more preferably 6 to 16 carbon atoms such as a phenyl group, and a hydrogen atom in an alkyl group having 1 to 50 carbon atoms, more preferably 1 to 18 carbon atoms. An alkyl group in which one or more of the following is substituted with a cyano group, a hydroxyl group, a carboxyl group, an acid amide group, an imide group, a sulfone group, an amino group, a glyceroyl group, or a group that can be converted into these groups by hydrolysis. Chlorosilane or alkoxysilane having 1 to 3 modifying groups or a plurality of the above chemical modifying groups, for example 6 to 10
Cyclosiloxane or polysiloxane having 0 is used. In addition, as the alkoxy group of the above alkoxysilane, a lower alkoxy group having 1 to 3 carbon atoms such as a methoxy group is suitable. Further, as the cyclosiloxane, one in which 3 to 50 silicon atoms form a ring via an oxygen atom is preferable. Preferably, the polysiloxane has 2 to 50 silicon atoms. Specific examples of such chemical modifiers include those shown in Table 1.

[0013]

[Table 1]

Among the chemical modifiers in the first step described above, monochlorosilane compounds such as dimethyloctadecylchloro(methoxy)silane and monoalkoxysilane compounds can also be used; however, dichlorosilane compounds such as methyloctadecyldichlorosilane, Trichlorosilane compounds such as octadecyltrichlorosilane, dialkoxysilane compounds such as methyloctadecyldimethoxysilane, trialkoxysilane compounds such as octadecyltrimethoxysilane, or 1,3,5,7-tetraoctadecyl-1,3,5,7- It is preferable to use a cyclosiloxane compound such as tetramethylcyclotetrasiloxane or a polysiloxane compound. That is, in the second step of end-capping, as described below, the higher the reaction temperature, the more the reaction progresses, and the fewer remaining silanol groups become. Elimination of the chemical modification group becomes more likely. However, by using a di- or trichlorosilane compound, a di- or trialkoxysilane compound, a cyclosiloxane compound, or a polysiloxane compound as a chemical modifier in the first step, the elimination of the chemical modification group during endcapping can be effectively prevented. The effect of preventing this desorption is greater when the above compound is used than when a monochloro or monoalkoxysilane compound is used.

[0015] The above-mentioned reaction of the chemical modifier to the silica gel or porous glass can be carried out using known methods and conditions. For example, chemical modification can be carried out by reacting the silica gel or porous glass with the chemical modifier in a solvent. can be done. In this case, a solvent that does not react with a chemical modifier such as toluene and is thermally stable at the reaction temperature can be used as the solvent. Moreover, the reaction temperature is usually in the range of 0 to 400°C, and the reaction time is in the range of 30 minutes to 72 hours.

In the second step of the present invention, the chemically modified silica gel or porous glass obtained in the first step is end-capped by a gas phase reaction without using a solvent. That is,
The chemically modified silica gel or porous glass obtained in the first step is reacted with an end capping agent in a gas phase at a temperature of 250° C. or higher to end cap residual silanol groups.

In this case, if the reaction temperature is lower than 250°C, the amount of silanol groups remaining will increase. Furthermore, there is no particular upper limit to the temperature; however, if the temperature becomes too high, the number of remaining silanol groups will decrease, but the chemical modification groups that are already chemically bonded to the silica gel or porous glass may become detached more often. , the upper limit thereof is preferably 500°C. In addition, the more preferable reaction temperature is 250 to 450°C.
, especially 250-400°C. Also, the reaction time is 30
It is desirable to set the time to about 96 minutes to 96 hours, more preferably 12 to 48 hours.

The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen, helium, or argon. In addition, the amount of the end capping agent introduced is appropriately selected and is not particularly limited, but may be 0.001 to 5 mmol/ml,
In particular, 0.01 to 1 mmol/ml is usual. In addition,
The end capping agent can be introduced as it is in gaseous or liquid form at 250 to 420°C.

The type of end capping agent used in the second step of the present invention is not limited, and various silazane compounds, silane compounds, siloxane compounds, etc. can be used. Specifically, disilazane of the following formula (1) , hydrogen silane of formula (2), alkoxysilane of formula (3), formula (4)
) and siloxane of formula (5) can be used.

[0020]

[Chemical formula 1]

As such an end capping agent, for example, hexamethyldisilazane, pentamethyldisiloxane, diethylmethylsilane, triethylsilane, trimethylmethoxysilane, hexamethyldisilane, etc. can be suitably used.

[0022] Furthermore, as the end-capping agent, a compound (hereinafter referred to as a cross-linked end-capping agent) whose one molecule reacts with two or more residual silanol groups can be preferably used. It is possible to obtain a filler having a structure in which an end capping agent is chemically bonded to a plurality of residual silanol groups in a cross-linked manner, and which is significantly less affected by the residual silanol groups. As such a crosslinking end capping agent, cyclosiloxane of the following formula (6), hydrogen siloxane of formula (7), alkoxysilane of formula (8), siloxane of formula (9), etc. can be used. .

[0023]

[Case 2]

Specific examples of the crosslinking end capping agent include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and 1,1,3,3-tetrasiloxane. Methyldisiloxane, 1,
1,3,3,5,5-hexamethyltrisiloxane, 1
, 3-dimethoxytetramethyldisiloxane, etc., and hexamethylcyclotrisiloxane is particularly preferred.

Furthermore, in the second step of the present invention, end-capping can be completed by one reaction, but two or more end-capping reactions can be performed sequentially, thereby reducing the influence of residual silanol groups. can be further reduced. Here, when performing two end-capping reactions sequentially, the above-mentioned crosslinked end-capping agent, especially hexamethylcyclotrisiloxane, is used as the end-capping agent for the first reaction, and the end-capping agent for the second reaction is It is preferable to use hexamethyldisilazane, as this can significantly reduce the influence of residual silanol groups.

[0026]

As explained above, since the manufacturing method of the present invention uses a gas phase method for the end cap, it is possible to obtain a filler with a small amount of residual silanol. This packing material has a small residual amount of silanol, so it has little adsorption to basic compounds. Therefore, columns packed with this packing material have fewer problems such as non-elution, adsorption, and tailing of basic compounds during analysis, and can be used for accurate analysis. can be done.

[0027]

[Examples] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

First, a packing material for liquid chromatography was manufactured by the following first and second steps.

First step: Chemical modification of silica gel A spherical silica gel with a pore diameter of about 100 Å and an average particle diameter of about 5 μm is reacted with a monochlorosilane compound, a dichlorosilane compound, or a trichlorosilane compound shown in Tables 2 and 3 as a chemical modifier, Octadecyl group on surface silanol group,
A phenyl group, n-butyl group, or 3-cyanopropyl group was chemically bonded.

In this case, 10 g of the above silica gel is
The mixture was vacuum dried at ℃ for 6 hours, and 40 ml of dry toluene, 20 mmol of a chemical modifier, and an equivalent amount of pyridine to the chemical modifier were added in an eggplant flask, and the mixture was reacted in an oil bath under toluene reflux for 16 hours. Next, it was filtered using a glass filter (G-4), and washed and filtered with 150 ml of toluene. Thereafter, when a monochlorosilane compound was used as the chemical modifier, operation (2) was performed, and when a dichlorosilane compound and a trichlorosilane compound were used, operation (2) was performed. ■ After washing and filtering with 150 ml of methanol and 100 ml of acetone,
Vacuum drying was performed at 120°C for 6 hours. ■ After washing and filtering with 100ml of acetonitrile, acetonitrile:water (
Add a mixture of 1:1), stir to hydrolyze unreacted chloro groups, filter using a glass filter (G-4), add 100 ml of methanol, and then add 100 ml of acetone.
The mixture was washed and filtered with , and vacuum dried at 120° C. for 6 hours.

[0031]

[Table 2]

Second step: End-capping 3 g of silica gel chemically modified in the first step and 2.9 mM of the silane compound for end-capping shown in Tables 3 and 4.
(for groups A to F) or 4.4mM (for group G
, H) were placed in a sealed container, the inside of the container was replaced with nitrogen, and the container was sealed. Next, this was placed in a constant temperature bath in Tables 3 and 4.
After heating at the temperature shown for the time shown in the same table, this was washed and filtered with toluene using a glass filter, further washed and filtered with methanol, and then vacuum-dried at 120° C. for 2 hours.

Next, elemental analysis of the obtained filler and examination of the influence of residual silanol groups were carried out using the following method. The results are shown in Tables 3 and 4.

Elemental analysis The obtained filler was subjected to elemental analysis, and the degree of elimination of the chemical modification group during endcapping was investigated by increasing or decreasing the carbon content. In this case, it is recognized that the smaller the amount of decrease in carbon content, the less the chemical modification group is eliminated.

Examination of the influence of residual silanol groups The obtained packing material was packed into a stainless steel column with an inner diameter of 4.6 mm and a length of 15 cm, and acetonitrile/water (volume ratio 30/70) was used as the mobile phase at a flow rate of 1. 1 per minute
150 μg/ml of pyridine and 1000 μg/ml of phenol under the analysis conditions of UV detector wavelength 254 nm.
A chromatogram was obtained by injecting 3 μl of a mixed sample containing the following. From this chromatogram, the tailing factor of pyridine and the separation coefficient α between pyridine and phenol were calculated.

In this case, the smaller the influence of the residual silanol, the faster the basic substance pyridine elutes compared to phenol, and the value of α becomes larger. Also, the tailing becomes smaller and the value of the tailing factor becomes smaller. Here, the tailing factor and separation coefficient α are defined as follows.

[0037]

[Math 1]

[0038]

[Table 3]

[0039]

[Table 4]

[0040] Here, the example groups A to H in the table are classified according to the following criteria. A: Using an octadecylmonochlorosilane compound as a chemical modifier B: Using an octadecyldichlorosilane compound as a chemical modifier C: Using an octadecyltrichlorosilane compound as a chemical modifier D: End-capping twice What was done E: Using a phenylmonochlorosilane compound as a chemical modifier F: Using a phenyldichlorosilane compound as a chemical modifier G: Using a phenyltrichlorosilane compound as a chemical modifier H: Chemical modifier In addition, in order to compare the performance of the packing material in the above example with that of a commercially available packing material, four types of typical commercially available ODS columns (
The tailing factor of pyridine and the separation coefficient α between pyridine and phenol in Comparative Examples 1 to 4) were investigated. The results are shown in Table 5.

[0041]

[Table 5]

Furthermore, Examples 4, 11, 16, 29, 36
, 37, 38 and the fillers of Comparative Examples 1 to 4, chromatograms of pyridine and phenol were obtained by liquid chromatography. The results are shown in Figures 2-12.

From the above results, the following points (1) to (4) can be understood. (1) The ODSs (groups A to D) in the examples are commercially available ODs.
Compared to S (Comparative Examples 1 to 4), the separation coefficient α between pyridine and phenol was large, and the tailing factor of pyridine was small. That is, by performing endcapping at a predetermined temperature in the gas phase, it was possible to synthesize a filler in which the influence of residual silanol groups is extremely small. (2) When silica gel is chemically modified with a dichlorosilane compound or trichlorosilane compound, the chemical modification group is less likely to be removed from the silica gel during endcapping in the gas phase, compared to when chemically modified with a monochlorosilane compound. We were able to synthesize a filler with a higher carbon content. Note that the degree of influence of residual silanol groups was the same regardless of which chlorosilane compound was used. (3) By using a silane compound that reacts with two or more silanol groups, such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, or tetramethyldisiloxane, for endcapping, the influence of residual silanol groups is further reduced. I was able to synthesize. This is considered to be because these silane compounds are chemically bonded in the form of a bridge on the silica gel surface around the modifying group, effectively covering the silica surface. (4) In the end-capping process, when end-capping is first performed using hexamethylcyclotrisilane and then end-capping is performed using hexamethyldisilazane, the amount of residual silanol groups is reduced compared to one-time end-capping treatment. The impact has become even smaller. However, when hexamethylcyclotrisiloxane or diethylmethylsilane was used for the second endcapping, it was not very effective.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method of calculating a tailing factor.

FIG. 2 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 4.

FIG. 3 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 11.

FIG. 4 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 16.

FIG. 5 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 29.

FIG. 6 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 36.

FIG. 7 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 37.

FIG. 8 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Example 38.

FIG. 9 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Comparative Example 1.

FIG. 10 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Comparative Example 2.

FIG. 11 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Comparative Example 3.

FIG. 12 is a chromatogram when pyridine and phenol were measured by liquid chromatography using the packing material of Comparative Example 4.

Claims (4)

[Claims] Claim 1: A step of reacting a chemical modifier with silica gel or porous glass to chemically bond the chemical modifier to silanol groups on the surface of the silica gel or porous glass; Liquid chromatography comprising the step of reacting an end-capping agent in a gas phase at a reaction temperature of 250° C. or higher to chemically bond the end-capping agent to residual silanol groups on the surface of silica gel or porous glass. Method for producing fillers for 2. The manufacturing method according to claim 1, wherein one or more selected from dichlorosilane compounds, trichlorosilane compounds, dialkoxysilane compounds, trialkoxysilane compounds, cyclosiloxane compounds, and polysiloxane compounds is used as the chemical modifier. . 3. The manufacturing method according to claim 1, wherein a compound whose one molecule reacts with two or more remaining silanol groups of the silica gel or porous glass is used as the end capping agent. 4. Silica gel or porous glass in which a compound and hexamethyldisilazane, one molecule of which reacts with two or more residual silanol groups of silica gel or porous glass, are used as end-capping agents, and these are sequentially chemically modified. 3. The manufacturing method according to claim 1 or 2, wherein the method is made to react with.