JP2003172733A - Manufacturing method for ods silica gel filler for liquid chromatography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for ODS silica gel filler capable of measuring a substance with satisfactory reproducibility by full end-capping ODS silica gel simply in a short time. <P>SOLUTION: In this method for manufacturing ODS silica gel filler, end capping is performed using two kinds or more of amine compounds and using octadecyl silylated silica gel as reaction accelerator, and then washing is performed by a washing liquid containing heated organic solvent and/or a washing liquid containing acid. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an ODS-modified silica gel packing material for liquid chromatography.

[0002]

2. Description of the Related Art A silica gel-based packing material for liquid chromatography (HPLC) has made dramatic progress by using high-purity silica gel as a raw material, and many stationary phases with extremely high separation selectivity have been developed and marketed. Has been done.
Among these, octadecyl silylated (ODS) silica gel filler has been a leading role in supporting the development of HPLC.
However, it is a well-known fact that this filler causes an irreversible secondary interaction due to silanol derived from silica gel as a problem since its development, and an object of eliminating this irreversible secondary interaction In the past, many techniques for deactivating (end capping) ODS-modified silica gel filler have been developed, reported, and put into practical use.

The typical techniques of end capping that have been reported so far are summarized as follows: Toluene reflux method In this method, toluene is used as a solvent, and trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) are used alone or as a mixture to obtain pyridine (K.
no, S. Shimura, N. Tanaka, JC Fetze, R. Biggs
Chromatographia, 27, 285 (1989)) or diethylamine (N. Tanaka, H. Kinoshita, M. Araki, J. Chrom
atogr., 332, 57 (1985)).

2. High-temperature liquid phase method TMCS and HMDS are added alone or as a mixture to the ODS-modified silica gel filler that has undergone primary end-capping at the reflux temperature of toluene, and the temperature is further increased (230 ° C to 250 ° C)
Two-step reaction with end capping. Closed system reaction (Makoto Hosoda, Yoshihiro Sakai Chromatography, 17, 39 (199
6)), liquid paraffin (Yoshihiro Sakai, Daiji Hamakawa, Suzue Ota 2nd LC Techno Plaza Lectures BP2, 51 (199)
7)) and Japanese Patent Laid-Open No. 2002-22721.

3. Gas phase method (JP-A-4-2212058)
No.) A method of synthesizing ODS-modified silica gel and then heating and reacting it with a silanizing agent in a closed container. One-step or two-step endcap reaction.

4. Supercritical method (Takashi Takada, Toshihide Ihara, Noriyuki Horimoto, Akira Nomura 4th LC Techno Plaza Lecture Abstract, BP2
36 (1999), Patent No. 2818857) After synthesizing ODS-modified silica gel, HM in a supercritical fluid
One-step endcap reaction with endcapping with DS etc. Among these, the type of end capping agent (silanizing agent) and reaction conditions (atmosphere, temperature, etc.) have been studied.

As described above, various end capping techniques have been developed. The toluene reflux method is the oldest and most popular end capping technique. What is characteristic of the method for synthesizing an ODS-modified silica gel filler under toluene reflux temperature (including end capping) that is currently used is that the base used for promoting the silylation reaction is both ODS-modified and end capped. The same compound is used. That is, if diethylamine (DEA) (secondary amine) is used as a reaction accelerator in the synthesis of ODS-modified silica gel, DEA is also used in end capping, and pyridine (tertiary amine) is converted into ODS-modified silica gel. When used in the synthesis of, the method using pyridine is also adopted for end capping. However, this toluene reflux method has a problem in that complete end capping is difficult even if the reaction is performed for a long time (24 hours or more).

In addition, the above 2. ~ 4. Is 1. Although it is a technique developed to make end capping more incomplete, it requires special conditions such as reaction atmosphere (in autoclave or supercritical fluid), and these methods However, since the ODS-modified silica gel filler is not fully end-capped, peak tailing occurs when analyzing coordinating compounds such as oxine copper and strongly basic compounds, and the measurement results are not reproducible. was there. On the other hand, recently, silica gel-based liquid chromatography (HPL
Regarding the filler for C), a large number of those having extremely high separation selectivity have been developed and marketed according to the intended use of the target component to be measured. For example, columns for golf course pesticide analysis, sugar analysis, amino acid analysis, and optically active substance analysis are commercially available. One of them, golf course pesticides, needs to be monitored in public water areas. In the 1993 version (clean water test method, 1993 version), in the clean water test method, 8 kinds of pesticides including oxine copper were analyzed by HPLC.
The method of testing with a column packed with ODS-modified silica gel packing is adopted by the method. However, the 2001 version of the clean water test method revised last year (clean water test method 2
In the (001 version), the packing of the column used as the first priority is changed from the ODS-modified silica gel-based packing to the polymer-based packing. It is considered that the reason why the use of the polymer-based filler is prioritized is that the elution of the target component is stable. That is, in the case of the ODS-modified silica gel filler, there is a residual silanol between lots of the ODS-modified silica gel filler. It is thought that this is because there is still quality variation. However, the polymer-based packing has a problem that the price is high, the number of theoretical plates of the column is low, and the separation of the target substance is insufficient.

Therefore, in the present water supply test method, when the ODS-modified silica gel filler is used, it is 50 m.
A mol / l potassium phosphate aqueous solution (pH 3.5) was used as an eluent, and ethylenediaminetetraacetic acid disodium (EDTA-2N) was used for the purpose of ensuring reproducibility.
The elution of copper oxine is stabilized by adding a) to the eluent. However, adding a basic substance such as EDTA-2Na to the eluent causes damage to the ODS-modified silica gel filler, shortens chemical durability, and
When EDTA-2Na enters a column with a large amount of residual silanol, it is difficult to discharge it out of the column, and there is a problem that reproducibility is likely to occur during general analysis.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, to easily perform full-end capping of ODS-modified silica gel in a short time, and to further improve the reproducibility of the target substance to a minute amount. ODS that can be measured
A method for producing a silica gel filler is provided.

[0011]

As a result of intensive studies to solve the above problems, the present inventors have found that the method for producing an ODS-modified silica gel filler requires mild reaction conditions and requires a special apparatus. The remaining silanol is completely eliminated by end-capping in a short time without cleaning, and cleaning with an organic solvent-containing cleaning solution and / or an acid-containing cleaning solution is performed. The present invention has been completed by finding a method for producing an ODS-modified silica gel filler capable of measuring a coordination compound or a strongly basic compound with a good peak shape with good reproducibility. That is, the present invention relates to a method for producing an ODS-modified silica gel filler, which comprises performing endcapping using two or more different amine compounds as reaction accelerators. The present invention also relates to the above method, wherein the two or more different amine compounds are a combination of a secondary amine and a tertiary amine. The invention further relates to said process, characterized in that the secondary amine is diethylamine and the tertiary amine is triethylamine. Furthermore, the present invention relates to the method, wherein the end capping is performed in two or more times.

The present invention relates to the above method, characterized in that each endcapping is carried out with amine compounds of different grades. The present invention also relates to the above method, characterized in that after each end capping, cleaning is performed with a cleaning liquid containing an organic solvent at a temperature of 30 to 110 ° C. and / or with a cleaning liquid containing an acid. The present invention also relates to the above method, wherein the cleaning after the primary end capping is performed with a cleaning liquid containing an organic solvent, and the cleaning after the secondary end capping is performed with a cleaning liquid containing an acid. The invention further relates to the above method, characterized in that the organic solvent is methanol. Furthermore, the invention relates to the above method, characterized in that the acid is phosphoric acid.

According to the present invention, the specificity of the silylation reaction (E. Colin "Silicon in Organic Synthesis" Buttrwo
rks 1981) and considering the structure of silanol on the surface of silica gel, end capping is performed using a different amine compound (which reacts with a silylating agent and acts on silica gel as a silylamine) to remove a washing solution containing an organic solvent and / or an acid. By cleaning with the cleaning liquid containing it, complete full-end capping, which was difficult in the past, can be performed easily in a short time without using special conditions and equipment.
It can be manufactured with good reproducibility even between batches. Also,
The ODS-modified silica gel filler obtained by the method of the present invention is
Elution of both extremely small amounts of metal coordinating compounds and basic compounds, which has been difficult without the use of polymer-based fillers in the past, is good and can be measured with good reproducibility. further,
ED using the ODS-modified silica gel filler according to the present invention
A coordinating compound and the like can be measured with an eluent containing no TA-2Na, and it is an excellent HPLC filler having chemical durability. Further, according to the present invention, even for a compound having a strong coordinating property such as oxine copper, the end capping of the ODS-modified silica gel filler is sufficiently performed, so that it does not cause an irreversible secondary interaction with the residual silanol. , Regardless of the material of the column, can be analyzed with good reproducibility.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Silica gel used in the present invention
50-800m for highly efficient chemical modification ²/ g ratio
Those having a surface area are preferably used. More preferably 20
0-400m²/ g. Furthermore, the particle size is 2 to 200 μ.
m, more preferably 2 to 15 μm, pore size 40 to 100
0 Å, more preferably 40 to 200 Å is suitable
Can be As ODS group chemically bonded to silica gel
Is a dimethyloctadecyl group, a methyloctadecyl group,
Having an octadecyl group such as an octadecyl group
Any of them can be used.

As the amine compound used as a reaction accelerator for ODS formation and end capping in the present invention, any of primary, secondary and tertiary amines can be used. Examples of the primary amine include ethylamine, butylamine, propylamine, and the like, and examples of the secondary amine include diethylamine (DEA), dibutylamine, diisopropylamine, morpholine, hexamethyldisilazane, and the like. Examples include triethylamine (TEA), tributylamine, pyridine and the like. A secondary amine such as diethylamine, hexamethyldisilazane, and a tertiary amine such as triethylamine and pyridine are preferably used because they are liquid at room temperature and are easy to use. Further combinations include diethylamine and triethylamine, and hexamethyldisilazane and pyridine.

As the method of endcapping the ODS-modified silica gel filler used in the present invention, a known method using toluene or liquid paraffin as a solvent is used.
When hexamethyldisilazane is used as the reaction accelerator, it is desirable to use liquid paraffin as the solvent for endcapping in a shorter time. End capping may be performed using any method as long as it is performed using two or more different amine compounds, for example, trimethylchlorosilane and different amine compounds are continuously added in the same reaction system, or It is also possible to carry out the end capping in two or more times, for example, by performing different reaction in different amine compounds separately. In order to complete the end capping performed by each reaction accelerator, it is preferable to perform the reaction in different reaction systems. Further, as the combination of different amines, those having different grades are preferable, and further, the combination of secondary and tertiary amine compounds is preferable.

For example, when a secondary amine such as DEA is used as a reaction accelerator for ODS formation, end capping is performed by using trimethylchlorosilane as a reaction accelerator in the presence of a secondary amine such as DEA and hexamethyldisilazane. Then, trimethylchlorosilane is allowed to act in the presence of a tertiary amine such as pyridine or TEA having a different grade, and full-end capping is performed. With a reaction time of 3 to 4 hours, elution of metal coordinating compounds (elution of oxine copper under acidic conditions, etc.) and strong base compounds (elution of benzylamine under neutral conditions, etc.) became favorable, resulting in complete hydrophobicity. Can be realized.

In addition, for example, when TEA which is a tertiary amine is used as a reaction accelerator in the ODS-forming reaction, the end capping causes trimethylchlorosilane to act as a reaction accelerator in the presence of a tertiary amine such as pyridine or TEA. After this, trimethylchlorosilane is allowed to act in the presence of secondary amines of different grades such as DEA and hexamethyldisilazane for full end capping. By reacting for 3 to 4 hours, the metal coordinating compound and the basic compound can be eluted. In addition, a known method such as JP-A-2002-22721 can be used for the ODS-forming reaction according to the present invention.

Further, in the present invention, it is preferable to wash the ODS-modified silica gel with a washing liquid containing a warm organic solvent after the end capping. In order to measure the target substance with good reproducibility, it is preferable to further wash with a washing liquid containing an acid. When the end capping is performed in two or more times, the cleaning solution containing an organic solvent and the cleaning solution containing an acid may be used for each cleaning, or the cleaning solution containing an organic solvent or the cleaning solution containing an acid may be used. Good. In this case, the order and the number of times of using the cleaning liquid containing the organic solvent and the cleaning liquid containing the acid are not limited. In order to efficiently remove the reaction promoter such as pyridine used at the time of primary endcapping and to allow the endcapping after the secondary endcapping to proceed sufficiently, use a cleaning solution containing an organic solvent after the primary endcapping and remove the acid after the secondary endcapping. It is preferable to wash with a washing liquid containing.

As the organic solvent, alcohols such as methanol, ethanol and denatured alcohol, aliphatic organic compounds such as hexane, acetone and ethyl acetate, aromatic organic compounds such as toluene and the like can be used. Methanol, which is relatively easy to handle and miscible with water, is preferably used. Further, if the ODS-modified silica gel after the primary endcapping is sufficiently washed, one kind of organic solvent may be used, two or more kinds of organic solvents may be used in combination, and two or more kinds of organic solvents may be mixed. You may use it. Further, the organic solvent miscible with water may be used in combination with water. In order to wash more efficiently, it is preferable to mix and use water and an organic solvent miscible with water. When methanol is used as an organic solvent miscible with water to prepare a methanol aqueous solution, its concentration is preferably 20 to 80%, more preferably 30 to 70%, and further preferably 40 to 60%. Further, in order to efficiently remove the reaction accelerator such as pyridine, it is preferable to use an organic solvent warmed to 30 to 110 ° C. When using a warm aqueous methanol solution, 20 to 70 ° C. is preferable and 5
0-60 degreeC is more preferable. If the washing with a washing solution containing a warm organic solvent is not carried out, the ODS-modified silica gel may turn brown during the reaction in the secondary end-capping step, and the ODS-modified silica gel filler intended by the present invention cannot be obtained. There is. This is because the amine as the reaction accelerator remains as a hydrochloride on the surface of the ODS-modified silica gel, and if secondary end capping is performed without removing the amine, the amine or the ODS-modified silica gel carbonizes due to the temperature increase. Seem. Therefore, in order to obtain the ODS-modified silica gel filler intended by the present invention,
It is necessary to completely remove the residual amine. The washing time is not particularly limited, but is preferably 30 minutes to 6 hours, and particularly preferably 3 to 4 hours.

After washing with a washing solution containing a warm organic solvent in the primary end capping, in order to enhance the washing effect of the ODS-modified silica gel, alcohols such as methanol, ethanol and denatured alcohol, hexane,
It is preferable to wash with an organic solvent such as an aliphatic organic compound such as acetone and ethyl acetate, an aromatic organic compound such as toluene, and dry. Further, the drying is preferably performed at 100 to 150 ° C. for 1 to 4 hours so as not to affect the secondary end capping. The cleaning method is OD
The S-silica gel may be immersed in a container such as a beaker containing an organic solvent for washing, may be washed with stirring, or may be directly applied with the organic solvent.

When washing with a washing solution containing an acid after the end capping, the acid is phosphoric acid, acetic acid, hydrochloric acid, sulfuric acid,
Etc. can be used, but phosphoric acid or acetic acid, which is relatively easy to handle and is commonly used for column washing, is preferably used. These acids may be used alone, in combination of two or more, or in combination of two or more, as long as they do not affect the durability of the ODS-modified silica gel filler. Also, these acids can be used as an aqueous solution. For efficient cleaning, it is preferable to use an acid aqueous solution. In that case, the concentration should not affect the durability of the ODS-modified silica gel filler,
When using a phosphoric acid aqueous solution, 0.5 to 5% is preferable,
0.5-1% is more preferable. Moreover, when using an acetic acid aqueous solution, 0.5 to 5% is preferable, and 0.5 to 1% is more preferable. Furthermore, if an acid and an alcohol such as methanol, ethanol or denatured alcohol, or an organic solvent such as an aliphatic organic compound such as acetone or ethyl acetate is mixed and used, residual organic substances such as paraffin can be removed, which is preferable. is there. The mixing ratio in this case is preferably 30/70 to 70/30 (vol / vol), and 40/60 to 60/40 (vol / vol) when using phosphoric acid aqueous solution / methanol as the acid / organic solvent. More preferable.

Since the end capping is performed under basic conditions, the surface of the ODS-modified silica gel is basic, and if it is left as it is, the interaction with the oxine copper is large and the elution becomes insufficient. In order to make the surface neutral, it is preferable to wash with a washing liquid containing an acid. Therefore, the ODS-modified silica gel-packed column obtained by washing with the washing liquid containing such an acid can easily and reproducibly analyze the target substance without performing column washing at the time of sample analysis. The washing time is not particularly limited, but 30 to obtain the ODS-modified silica gel filler aimed at by the present invention.
Minutes to 6 hours are preferable, and 3 to 4 hours are particularly preferable. After washing with a washing liquid containing an acid, it is preferable to further wash with an organic solvent and dry in order to enhance the washing effect of the ODS-modified silica gel. As the organic solvent in this case, alcohols such as methanol, ethanol and denatured alcohol, aliphatic organic compounds such as hexane, acetone and ethyl acetate, and organic solvents such as aromatic organic compounds such as toluene can be used. Methanol is preferably used to remove phosphoric acid and the like. Then, in order to completely dry the ODS-modified silica gel after end-capping, it is preferable to dry it at 120 ° C. for 2 hours. The ODS-modified silica gel packing thus produced is packed in a column and used for HPLC measurement. The material of the column may be stainless or resin such as polyethylene, polypropylene or polystyrene.

There is no particular limitation on the substance that can be measured with the ODS-modified silica gel filler according to the present invention. For example, golf course pesticides such as oxine copper, thiuram, ashram, mecoprop and bensulide, carbamate pesticides such as aldicarb and methiocarb, basic substances such as benzylamine and procainamide, organic acids such as benzoic acid, sorbic acid and dehydroacetic acid. And various esters such as caffeine and phenol. Of these, oxine copper, which has been difficult to analyze with good reproducibility, can be particularly preferably applied. INDUSTRIAL APPLICABILITY According to the present invention, it becomes possible to produce an ODS-modified silica gel filler in which residual silanol which causes an irreversible secondary interaction is completely end-capped, and a washing with a warm aqueous methanol solution after the primary end-capping is performed. By washing with a 1% phosphoric acid aqueous solution / methanol mixed solution after the next end capping, it became possible to stably elute 1 ng of oxine copper without special pretreatment (addition of EDTA-2Na etc.). .

[0025]

[Example 1] Effect of end capping (1) Synthesis of ODS-modified silica gel filler ODS of silica gel was synthesized by performing acid washing of silica gel and then performing silylation reaction. (1) -1. Washing of silica gel Silica gel for liquid chromatography (particle size 5 μm,
Specific surface area 350 m ² / g, pore diameter 12 nm, pore volume 1.1 ml / g) 50 g 6 mol / l hydrochloric acid 200 ml
Heat at reflux for 5 hours. After filtration, the silica gel is washed with pure water until the filtrate becomes neutral. Then, it is washed with 50 ml of acetone and dried at 130 ° C. for 4 hours.

(1) -2. Synthesis of ODS-modified silica gel filler (ODS-DEA) by combination of secondary amine (DEA) and tertiary amine (TEA) <ODS conversion> 25 g of hydrochloric acid washed silica gel in a 1 liter round bottom four-necked flask. And dry toluene 500m
Disperse in l. Thereafter, 45 g of dimethylchlorooctadecylsilane (DMCODS) and 25 g of DEA are sequentially added, and the mixture is heated under reflux for about 5 hours. The product is filtered and then tetrahydrofuran (THF) 200 ml · methanol (MeO
H) Wash sequentially with 100 ml and dry at 120 ° C. for 4 hours. This filler is designated as ODS-D-1.

<Primary End Capping> Filler OD
25 g of SD-1 was dispersed in 500 ml of dry toluene, and 10 ml of trimethylchlorosilane (TMCS) and D were added.
20 ml of EA is added and the mixture is heated under reflux for 3 to 4 hours to complete the silylation reaction with the secondary amine. The product is filtered, washed successively with 200 ml of THF and 100 ml of MeOH, and dried at 120 ° C. for 4 hours. This filler is ODS
-D-2. <Secondary End Capping> Filler ODS-D-2,
Disperse 20 g in 300 ml of dry toluene and add TMCS
Add 10 ml of TEA and 20 ml of TEA and heat under reflux for 3 to 4 hours for end capping. The product is THF20 after filtration
It is washed successively with 0 ml and 100 ml of MeOH and dried at 120 ° C. for 4 hours. The ODS-modified silica gel filler thus synthesized is called ODS-DEA.

(1) -3. Synthesis of ODS-modified silica gel filler by combination of tertiary amine (TEA) and secondary amine (DEA) (ODS-TEA) <ODS conversion> 25 g of silica gel washed with hydrochloric acid was placed in a 1 liter round bottom four-necked flask. 500 ml of dry toluene
Disperse into Then DMCODS 45g, TEA25
g are added sequentially and the mixture is heated under reflux for about 5 hours. The product is filtered, washed successively with 200 ml of THF and 100 ml of MeOH, and dried at 120 ° C. for 4 hours. This filler is ODS-T-
Set to 1.

<Primary End Capping> Dry filler ODS-T-1 (25 g) was added to dry toluene (500 ml).
Then, 10 ml of TMCS and 20 ml of TEA are added and the mixture is heated under reflux for 3 to 4 hours to complete the silylation with the tertiary amine. The product is THF 200 ml, Me
It is washed successively with 100 ml of OH and dried at 120 ° C. for 4 hours. This filler is designated as ODS-T-2. <Secondary end capping> Filler ODS-T-2,
Disperse 20 g in 300 ml of dry toluene and add TMCS
Add 10 ml and 20 ml of DEA and heat under reflux for 3-4 hours. The product was filtered, 200 ml of THF, 1 MeOH
It is washed successively with 00 ml and dried at 120 ° C. for 4 hours. The ODS-modified silica gel filler synthesized in this manner is used as an OD.
S-TEA.

(2) Evaluation of ODS-modified silica gel filler Each synthesized ODS-modified silica gel filler was packed in a stainless steel column having an inner diameter of 4.6 mmφ and a length of 150 mm by the slurry method, and the end capping was evaluated. Evaluation of end capping was performed by measuring oxine copper (pH 2.1 eluent) and benzylamine (pH 7.6 eluent) by HPLC.

The elution test conditions are shown below. Oxin copper elution test conditions Eluent: 20 mmol / l phosphoric acid aqueous solution: acetonitrile = 95: 5 Flow rate: 1.0 ml / min Temperature: 40 ° C. Detection: UV 250 nm Test material: 5 μl (uracil; 4.5 μg, oxine) Copper; 20 μg, caffeine 150 μg / ml)

Benzylamine Elution Test The benzylamine test is based on the Tanaka test (K. Kimata, K. Iwag
uchi, S. Onishi, K. Jinno, R. Eksteen, K. Hosoya,
M. Araki, N. Tanaka, J. Chromatogr. Sci., 721, 27,
1989) is a method for confirming the quality of ion-exchange silanols, but the pH around neutral (pH =
The benzylamine elution state is measured under 7.6). The elution conditions are shown below. Eluent: 20 mmol / l potassium phosphate aqueous solution:
Methanol = 70: 30 Flow rate: 0.6 ml / min Temperature: 40 ° C. Detection: UV 254 nm Sample: 10 μl (benzylamine 0.59 mg,
Phenol 0.41 mg / ml)

(3) Results and Discussion The elution situation of oxine copper and benzylamine of the two kinds of fillers synthesized according to the above method is shown in FIG. 1 (ODS-D).
EA) a), b) and FIG. 2 (ODS-TEA) a),
Shown in b). Conventionally, the pyridine / phenol method has been widely used as a means for judging the quality of end capping, but this time, we are able to confirm the quality of end capping more severely than this method, and the oxine copper evaluation (coordinating compound and Two methods were adopted: a method of confirming the interaction of silanol) and an evaluation of benzylamine (a method of confirming the interaction between the ion-exchangeable silanol and the strongly basic compound). The oxine copper test is a test for confirming hydrogen-bonding silanols that are activated in the vicinity of weak acidity, and the benzylamine test is a test for confirming the presence of neutral ion-exchange silanols.

As shown in FIGS. 1a), b) and 2a), b), oxine copper and benzylamine elute with good peak shapes in both ODS-DEA and ODS-TEA. Especially, the peak symmetry of oxine copper is ODS-D.
The result was 1.33 for EA and 1.30 for ODS-TEA. This means that the irreversible interaction with the filler was small, which means that the endcapping proceeded well. Thus, it was revealed that the method of synthesizing an ODS-modified silica gel filler according to the present invention enables the synthesis of a completely inactivated ODS-modified silica gel filler, which has been difficult in the past.

[Example 2] Synthesis of ODS-modified silica gel filler (1) ODS-modified high purity silica gel a for liquid chromatography washed with 6 mol / l hydrochloric acid and dried (particle diameter 5 µm, surface area 2
70 m ² / g, pore diameter 13 nm, pore volume 1.0 ml
50 g / g) are dispersed in 500 ml of dry toluene. Dimethylchlorooctadecylsilane (DMC
ODS) 90g, and then diethylamine (DEA)
Add 50 ml and heat to reflux for about 5 hours. After cooling, the product was collected by filtration, 500 ml of tetrahydrofuran (THF),
After washing with 500 ml of methanol (MeOH) and 500 ml of 50% aqueous methanol solution, it is dried at 120 ° C. for about 2 hours. As a result, ODS-modified silica gel having a hydrocarbon content of 15% was obtained. Similarly, high-purity silica gel b
(Particle size 5 μm, surface area 340 m ² / g, pore size 12 n
m, pore volume 1.1 ml / g), silica gel b
When was used, ODS-modified silica gel having a hydrocarbon content of 20% was obtained.

(2) 50 g of ODS-modified silica gel a having a hydrocarbon content of 15% obtained in the primary end capping (1) is dispersed in 500 ml of dry toluene. Trimylchlorosilane (TMCS) 20m
1 and 25 ml of pyridine are sequentially added, and the mixture is heated under reflux for about 5 hours. After the reaction was completed, the product was collected by filtration, and THF (500 ml) was used.
MeOH 500ml, 50% MeOH aqueous solution 500ml
Washed with 50% MeOH aqueous solution for 3-4 hours 50
Heat wash at ~ 60 ° C. After filtration, wash with MeOH, 1
Dry at 20 ° C. for about 2 hours. ODS with 20% hydrocarbon content
Primary end capping was similarly performed on 50 g of silica gel b.

(3) Secondary end-capping Using ODS-modified silica gel a having a hydrocarbon content of 15%,
25 g of ODS-modified silica gel whose primary end capping is completed in (2) is dispersed in 500 ml of liquid paraffin. To this, 5 ml of TMCS and 17 ml of hexamethyldisilazane (HMDS) are added, and the mixture is reacted at a temperature of about 230 ° C. for about 3 hours. After cooling, the product is collected by filtration and hexane 30
After sequentially washing with 0 ml, THF 300 ml, MeOH 300 ml and 50% MeOH aqueous solution 300 ml, 1
% Phosphoric acid aqueous solution / MeOH = 50/50 (vol / vo
l) Wash with 250 ml at 60 ° C. for 2 hours. 50% M
Heat and reflux for 3 to 4 hours with an aqueous OH solution for washing. After filtration, it is washed with 300 ml of MeOH and then dried at 120 ° C. for 2 hours. Thereby, the ODS which is the object of the present invention
The silica gel filler (hereinafter abbreviated as ODS silica gel filler A) could be synthesized. Hydrocarbon amount 20
The second end capping was similarly performed on 25 g of the ODS-modified silica gel b (25 g) to synthesize an ODS-modified silica gel filler (hereinafter abbreviated as ODS-modified silica gel filler B).

Example 3 Cleaning Effect After Primary End Capping In order to compare the cleaning effect after primary end capping, Example 2 and ODS-modified silica gel filler B synthesized using silica gel b in Example 2. 50 in (2)
The oxine copper was analyzed using the ODS-modified silica gel filler obtained in the same manner as in Example 2 except that the washing with a% MeOH aqueous solution was not performed. The elution test of oxine copper was basically carried out in accordance with the HPLC conditions of the clean water test method 1993 edition, but EDTA-2Na was used as the eluent without addition. The measurement conditions are shown below. The column used had a length of 1 by the packing method of the present invention by the slurry method.
It was packed in a stainless steel column with a diameter of 50 mm and an inner diameter of 4.6 mm, and anthracene was used as a sample to have a theoretical plate number of 90000.
A column having a column performance of 0 plate / mm or more was used. The measurement conditions (pH is 3.5) of HPLC for oxine copper are shown below. Eluent: 50 mmol / l potassium phosphate aqueous solution: acetonitrile = 60: 40 Detection: UV 230 nm Temperature: 40 ° C. Flow rate: 1 ml / min Injection volume: 1 μl (Oxine copper solution 1 μg / ml; Preparation method: Purified Water Test Method 2001 Edition) The results are shown in FIG. a) shows the OD when the secondary end capping was performed after washing with warm methanol, and b) the OD when the secondary end capping was performed without washing with warm methanol.
It is a chromatogram of copper oxine which used the S-ized silica gel filler. The peak at around 4 minutes was for oxine copper, and from FIGS. 3a) and 3b), when warm methanol washing was performed after endcapping, oxine copper as small as 1 ng could be eluted. When secondary end capping is performed without warm methanol washing, 1
Elution with reproducibility up to a very small amount of ng cannot be performed. It is considered that this is because the reaction solution is colored as the temperature at the end capping in the secondary end capping step increases, that is, the ODS-modified silica gel and the remaining reaction accelerator carbonize.
Therefore, it was found that it is necessary to sufficiently remove the reaction promoter and sufficient washing at the time of primary end capping in order to perform the analysis to a minute amount of 1 ng.

[Example 4] Cleaning effect after secondary end cap In order to compare the cleaning effect after secondary end capping, Example 2 and ODS-modified silica gel filler A synthesized using silica gel a in Example 2. Oxine copper was analyzed using the ODS-modified silica gel filler obtained in the same manner as in Example 2 except that the washing was not performed with the 1% phosphoric acid aqueous solution / methanol mixed solution in (3). The result is shown in Figure 4.
Shown in. a) shows the case of washing with 1% phosphoric acid aqueous solution / methanol mixed solution, and b) shows the case of not washing with 1% phosphoric acid aqueous solution / methanol mixed solution. It is a peak. The elution conditions and the column used are the same as in Example 3 (injection volume 1 μl). Figure 4
In b), 1 ng oxine copper could only confirm a slight peak, but in FIG. 4 a), it was revealed that a good peak shape was shown from the beginning even in the measurement of 1 ng. Therefore, it was found that the elution of oxine copper was improved by performing sufficient washing with the phosphoric acid aqueous solution / methanol mixed solution after the secondary endcapping.

[Example 5] Analysis of copper oxine using a column packed with the ODS-modified silica gel packing material synthesized in Example 2 ODS-modified silica gel packing materials A, B and EDTA-2N
1 ng of oxine copper was measured using an eluent having a pH of 3.5 and not containing a. The chromatogram is shown in FIG.
The elution conditions and the column used were in accordance with the conditions described in Example 3, and 1 μl was injected. It was confirmed that oxine copper was eluted with a good peak shape using any of the ODS-modified silica gel fillers.

[Example 6] Elution behavior of oxine copper by resin column and stainless steel column Elution behavior of oxine copper by using the peak resin column and stainless steel column was compared. The result is shown in FIG. For each column, ODS-modified silica gel packing A was used, the elution conditions and the column used were in accordance with Example 3 (injection volume 20 μl). As shown in FIG. 6, almost no difference was observed in the elution behavior.
Therefore, the elution behavior of oxine copper is determined by the ODS of the present invention.
It was confirmed that the use of the silica gel packing material does not affect the material of the column.

[Example 7] Measurement of reproducibility in detection ODS-modified silica gel packing A was packed by the method described in Example 3, and a column having a theoretical plate number of 90,000 plates / m or more was used. 1n under the eluent of the water test method
The reproducibility of g, 5 ng and 10 ng of oxine copper was measured. As a comparative test, a column (golf pack: manufactured by Waters) packed with a polymer filler having no irreversible secondary interaction with oxine copper was similarly tested. The results are shown in the table. The coefficient of variation (CV value) was measured 5 times at each concentration and calculated from the area value. The elution conditions were in accordance with Example 3.

[0043]

[Table 1]

As shown in the table, the coefficient of variation of the peak area showing the reproducibility was 9% in the measurement of 1 ng of the oxine copper analytical column of the present invention. It was also found that the coefficient of variation decreases as the amount of oxine copper injected increases to 5 ng and 10 ng. Comparing these coefficients of variation with those of polymer columns, it was also found that there was almost no difference between the two. Further, the present invention satisfies the area variation coefficient of 20% or less at the concentration of 20 ng shown in the water supply test method, and further, when analyzing the detection limit of 5 ng indicated by the Ordinance of the Ministry of the Environment, the variation coefficient of peak area is 5.46. %, Which is a good value.

Comparative Example 1 Effect on Elution of Basic Compound When End Capping is Performed Once with One Kind of Amine Compound Elucidation of Role of Reaction Accelerator in Synthesis of ODS-modified Silica Gel Filler In order to TEA ODS-D-1
DEA-TMCS with filler and ODS-T-1 endcapped once with TMCS (tertiary silyl amine)
The effect of the reaction promoter on the elution of the basic compound in the ODS formation and the end capping was compared by evaluating the elution state of benzylamine using the filler which was endcapped once with (secondary silylamine).

The results are shown in FIGS. 7a) and 7b). The elution conditions and the column used are the same as in Example 1. The results in FIG. 7 show the results that well represent the role of the silylating agent. 8
There is a peak of benzylamine around minute, but ODS-D
The packing material obtained by endcapping -1 with TEA-TMCS shows a strong tailing peak of interaction in the elution of benzylamine. However, ODS-T
The packing material obtained by end-capping -1 with DEA-TMCS (secondary silylamine) shows a relatively good chromatogram. This result suggests that the endcapping with the secondary silylamine is effective for elution of the basic substance.

Comparative Example 2 Effect on Elution of Metal Coordinating Compound When End Capping is Performed Once Using One Amine Compound The role of the reaction accelerator in the synthesis of ODS-modified silica gel filler To elucidate, ODS-T-1, ODS
-T-1 end-capping filler with DEA-TMCS (secondary silylamine), and ODS
-Effects of ODS-T-2, which has been endcapped once with TEA-TMCS (tertiary silylamine), on T-1 and the elution of the metal coordinating compound of the reaction promoter in ODS formation and endcapping Were compared. FIG. 8 shows the state of elution of the metal coordinating compound.
In this case dehydroacetic acid was used as a sample for evaluation. The reason is that the use of oxine copper is the best solution, but if the end capping is insufficient, oxine copper does not elute as shown in FIG. 9, so dehydroacetic acid, which is relatively easy to elute, is selected. did.

FIG. 8a) is a chromatogram of ODS-T-1, and FIG. 8b) is DEA-TMCS on ODS-T-1.
Chromatogram of packing material (same as FIG. 7b) endcapped once with (secondary silylamine), FIG.
c) is a chromatogram of ODS-T-2, and dehydroacetic acid has a peak around 9 minutes. The elution conditions are shown below. Elution condition (pH = 4.6) Eluent: 20 mmol / l aqueous sodium acetate: acetonitrile = 2: 1 Flow rate: 0.5 ml / min Temperature: 40 ° C. Detection: UV 254 nm Injection volume: 5 μl (sample: sorbic acid 20 mg , Benzoic acid 20 mg, dehydroacetic acid 20 mg / l) When comparing FIGS. 8 a) and b), almost the same chromatograms are obtained for the unendcapped product ODS-T-1 and the DEA-TMCS endcapped product. In particular, the packing material shown in FIG. 8b) has a problem in elution of dehydroacetic acid, even though benzylamine is relatively well eluted as shown in FIG. 7b). This result shows that even if a single end capping is performed using a secondary silylamine with an amine compound different from ODS formation, there is almost no effect on the elution of the metal coordinating compound. However, the TEA- shown in FIG.
It was confirmed that dehydroacetic acid was eluted without interaction in the ODS-T2 filler which was endcapped once with TMCS (tertiary silylamine). These results suggest that the endcapping with tertiary silylamine is effective for the elution of metal coordinating compounds.

[Comparative Example 3] Elution state when one type of amine compound was used and endcapping was carried out twice. FIG. 10 shows the case where ODS-D-1 in Example 1 was used.
The results of the ODS-modified silica gel filler subjected to endcapping twice using a secondary amine as a reaction accelerator are shown. A) shows oxine copper, and b) shows benzylamine chromatograms. The elution conditions are the same as in Example 1. The basic compound benzylamine (peak around 6 minutes) eluted relatively well, but oxine copper (peak around 5 minutes) showed strong chromatogram with strong adsorption and tailing. It shows that the elution of the basic compound is effective, but the elution of the metal coordinating compound is not improved.

As can be seen from the results of the comparative examples, it is shown that complete inactivation of the ODS-modified silica gel filler is difficult as long as the same reaction promoter is used for the two end cappings. As described above, the ODS-modified silica gel filler synthesized by using a secondary amine as a reaction accelerator is endcapped with TMCS in the presence of the secondary amine, and then the tertiary amine By further endcapping with TMCS in the presence,
Also, O synthesized by using a tertiary amine as a reaction accelerator
DS silica gel filler is used in the presence of tertiary amine
By performing endcapping with CS, and then further endcapping with TMCS in the presence of a secondary amine, it was revealed that complete hydrophobization that elutes a strongly basic compound and a metal coordinating compound without interaction can be realized. became.

[Comparative Example 4] Elution test of oxine copper according to the clean water test method EDTA-2 was tested by the clean water test method using various columns.
Oxine copper was measured comparatively using an eluent without addition of Na.
The column used was packed with ODS-modified silica gel packing A by the method described in Example 3, and the theoretical plate number was 90,00.
Wakosil-Cu, Wakopak Navi C18-5 GT (manufactured by Wako Pure Chemical Industries), GL ODS-Cu (manufactured by GL Science Co.), Capcell Pac
k UG 120 (manufactured by Shiseido Co., Ltd.) was used, and each column had a length of 150 mm and an inner diameter of 4.6 mmφ. The results are shown in Fig. 11. The elution conditions were in accordance with Example 3 (injection volume 20 μl). The chromatogram is a) OD
Column packed with S-silica gel packing material A, b) Wakosi
l Cu, c) Wakopak Navi C18-5 GT, d) GL ODS-Cu,
e) The results of Capcell Pack UG120A are shown, and the peak around the retention time of about 3 to 4 minutes indicates oxine copper.
As shown in a), it can be seen that the column packed with the ODS-modified silica gel packing A exhibits a good peak shape, but the other columns have irreversible secondary interactions except for c). It is strong and almost difficult to detect as a peak. The columns c) and d) are both columns that are marketed for the analysis of oxine copper by evaluating the columns by the clean water test method.
11a-e for the eluent without addition of TA-2Na.
As shown in, it was clarified that it showed a very strong secondary interaction.

[Comparative Example 5] p in the elution of copper oxine
Conventionally, HPLC analysis of H-dependent oxine copper often uses a strongly acidic eluent around pH2, and it can be seen that the secondary interaction becomes stronger as the pH is raised. Is basically any p
Even in H, oxine copper needs to be eluted. Therefore, the pH dependence of the elution of oxine copper was measured. As the ODS-modified silica gel packing material used, the one packed with ODS-modified silica gel packing A by the method described in Example 3 and having a column performance of 90,000 theoretical plates / m or more was used. . The measured pH is 2.1, 3.5, 4.
HPLC conditions other than the eluent were used according to Example 3 (injection volume 20 μl). The result is shown in FIG.
As shown in FIG. 12, it was confirmed that the column packed with the ODS-modified silica gel filler A was able to elute oxine copper satisfactorily, although the elution time was delayed as the pH was increased.

On the other hand, the same measurement was carried out on columns of other companies. The results are shown in Figures 13a to 15c. pH
In the case of 2.1 (Fig. 13a, Fig. 14a, Fig. 15a), a relatively good peak shape is shown, but the secondary interaction between the oxine copper and the filler becomes stronger as the pH becomes higher, and the elution It became clear that it was difficult. In particular, Capcell Pak C18UG 120A in FIGS.
5 shows a better peak shape than other columns (FIG. 15b), but at pH 4.5, elution time is delayed and peak tailing is increased,
The secondary interaction between the filler and copper oxine is clearly visible (Fig. 15c). The result is Capcell Pak C18U
G 120A is considered a filler with high residual silanols. The reason why the secondary interaction of oxine copper becomes stronger as the pH of the eluent increases in this way is that when the pH of the eluent becomes higher, the residual silanol groups on the surface of the filler are activated, and the oxine of the oxine copper increases. It is thought to be due to the formation of hydrogen bonds with.

[0054]

According to the present invention, by cleaning the ODS-modified silica gel with a cleaning liquid containing an organic solvent and / or a cleaning liquid containing an acid after end-capping, a reproducible and durable ODS-modified silica gel filler can be obtained. It has become possible to manufacture. In addition, the ODS-modified silica gel filler according to the present invention has made it possible to analyze low-concentration oxine copper with high accuracy and reproducibility, and further to analyze it using an eluent containing no EDTA-2Na.

[Brief description of drawings]

FIG. 1 OD by the end capping method of the present invention
The evaluation result of the S-DEA filler is shown. a) Copper oxine test (Chromatograms are uracil,
Indicates oxine copper and caffeine. ) B) Benzylamine test (Chromatogram shows benzylamine and phenol in this order.) The elution conditions are shown in Example 1 (2).

FIG. 2 OD by the end capping method of the present invention
The evaluation result of the S-TEA filler is shown. a) Chromatogram of oxine copper test (Chromatogram shows uracil, oxine copper, and caffeine in order) b) Chromatogram of benzylamine test (Chromatogram shows benzylamine and phenol in order.) This is shown in Example 1 (2).

FIG. 3 shows the effect of warm methanol wash after primary endcapping. a) Chromatogram when washed with warm methanol b) Chromatogram elution conditions when not washed with warm methanol are shown in Example 3. The peak near 4 minutes is oxine copper.

FIG. 4 shows the cleaning effect of a 1% phosphoric acid aqueous solution / methanol mixed solution after secondary endcapping. a) Chromatogram when washed with 1% phosphoric acid aqueous solution / methanol mixed solution b) Chromatogram elution conditions when not washed with 1% phosphoric acid aqueous solution / methanol mixed solution are shown in Example 3. The peak around 3 minutes is oxine copper.

FIG. 5 shows the results of elution of oxine copper by a column packed with the ODS-modified silica gel packing material synthesized in Example 2. a) Chromatogram when ODS-modified silica gel filler A is used b) Chromatogram when ODS-modified silica gel filler B is used Elution conditions are shown in Example 3. The injection volume was 1 μl. The peak around 3 minutes is oxine copper.

FIG. 6 shows a comparison between a peak resin column and a stainless steel column. a) Chromatogram of peak resin column b) Chromatogram of stainless steel column Elution conditions are shown in Example 3. The peak around 3 minutes is oxine copper.

FIG. 7 is a chromatogram showing the elution state of benzylamine when endcapping was performed once using one type of reaction accelerator. a) Chromatogram of the packing material in which ODS-D-1 is end-capped with TEA-TMCS (peaks are benzylamine and phenol in order) b) Chromatogram of the packing material in which ODS-T-1 is end-capped with DEA-TMCS ( The peaks are benzylamine and phenol in this order. The elution conditions are shown in Example 1 (2).

FIG. 8 is a chromatogram showing the elution state of dehydroacetic acid when one end capping was performed using one type of reaction accelerator. a) ODS-T-1 chromatogram (peaks are in order benzoic acid, sorbic acid, dehydroacetic acid) b) ODS-T-1 endcapped with DEA-TMCS Chromatogram (peaks are in order benzoic acid, Sorbic acid, dehydroacetic acid) c) Chromatogram of ODS-T-2 (peaks are benzoic acid, sorbic acid, dehydroacetic acid in order) Elution conditions are shown in Comparative Example 2.

FIG. 9 is a chromatogram showing the elution state of copper oxine using a filler obtained by end-capping ODS-T-1 with a secondary silylamine (chromatograms are uracil and caffeine in that order). The elution conditions are those in Example 1.
It is shown in (2).

FIG. 10: ODS-D-1 with secondary silylamine 2
The evaluation results of the filler that has been end-capped once are shown. a) Chromatogram of oxine copper test (peaks are uracil, oxine copper, and caffeine in sequence) b) Chromatogram of benzylamine test (peaks are benzylamine and phenol in sequence) Elution conditions are shown in Example 1 (2) .

FIG. 11a: Eluent pH 3.5 (EDT for the water test method)
Fig. 7 shows the elution behavior of oxine copper (20 ng) when using a column packed with ODS-modified silica gel packing A synthesized in Example 2 using (A-2Na-free). The elution conditions are
This is shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 11b: Eluent pH 3.5 (EDT of the clean water test method)
Fig. 7 shows the elution behavior of oxine copper (20 ng) when using a Wakosil-Cu column using A-2Na (no A). The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 11 c: Eluent pH 3.5 (EDT of the water test method)
Fig. 7 shows the elution behavior of oxine copper (20 ng) when using a Wakopak Navi C18-5 column using A-2Na (no A). The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 11d: Eluent pH 3.5 (EDT of the water test method)
8 shows the elution behavior of oxine copper (20 ng) when using a GL ODS-Cu column with A-2Na (no A). The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 11e: Eluent pH 3.5 (EDT for the water test method)
Fig. 7 shows the elution behavior of oxine copper (20 ng) when using a Capcell Pak UG 120A column using A-2Na (no A). The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 12 shows results of pH dependence in elution of copper oxine by a column packed with ODS-modified silica gel packing A. a) In the case of pH 2.1 b) In the case of pH 3.5 c) In the case of pH 4.5 The elution conditions are shown in Example 3. The peak around 3 to 5 minutes is oxine copper.

FIG. 13a shows a chromatogram for elution of copper oxine with Wakosil Cu at pH 2.1. The elution conditions are shown in Example 3. The peak around 4 to 5 minutes is oxine copper.

FIG. 13b shows the spectrum for elution of copper oxine with Wakosil Cu at pH 3.5. The elution conditions are shown in Example 3. The peak around 4 to 5 minutes is oxine copper.

FIG. 13c shows a chromatogram for elution of oxine copper with Wakosil Cu at pH 4.5. The elution conditions are shown in Example 3. The peak around 4 to 5 minutes is oxine copper.

FIG. 14a shows a chromatogram at pH 2.1 in the elution of copper oxine with GL ODS-Cu. The elution conditions are shown in Example 3. The peak around 3 to 5 minutes is oxine copper.

FIG. 14b shows a chromatogram at pH 3.5 in the elution of copper oxine with GL ODS-Cu. The elution conditions are shown in Example 3. The peak around 3 to 5 minutes is oxine copper.

FIG. 14c shows a chromatogram at pH 4.5 in the elution of copper oxine with GL ODS-Cu. The elution conditions are shown in Example 3. The peak around 3 to 5 minutes is oxine copper.

FIG. 15a shows a chromatogram for elution of copper oxine with Capcell Pak C18UG 120A at pH 2.1. The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 15b shows a chromatogram for the elution of copper oxine with Capcell Pak C18UG 120A at pH 3.5. The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

FIG. 15c shows a chromatogram at pH 4.5 in the elution of copper oxine with Capcell Pak C18UG 120A. The elution conditions are shown in Example 3. The peak around 3 to 4 minutes is oxine copper.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Suzue Ota             1-7-1 Inari, Soka City, Saitama Kanto Chemical Co., Ltd.             Ceremony company grass processing plant (72) Inventor Ichiro Tajima             1-7-1 Inari, Soka City, Saitama Kanto Chemical Co., Ltd.             Ceremony company grass processing plant F-term (reference) 4G066 AD01B EA01 FA11 FA33

Claims (9)

[Claims] 1. A method for producing an ODS-modified silica gel filler, which comprises performing endcapping using two or more different amine compounds as reaction accelerators.
The method. 2. A method according to claim 1, characterized in that the two or more different amine compounds are a combination of secondary and tertiary amines. 3. The secondary amine is diethylamine,
Process according to claim 2, characterized in that the tertiary amine is triethylamine. 4. The method according to claim 1, wherein the end capping is performed twice or more. 5. The end capping is carried out using amine compounds of different grades.
4. The method according to any one of 4 above. 6. The method according to claim 1, wherein after each end capping, cleaning is performed with a cleaning solution containing an organic solvent at a temperature of 30 to 110 ° C. and / or with a cleaning solution containing an acid. Method. 7. The method according to claim 1, wherein the cleaning after the primary end capping is performed with a cleaning liquid containing an organic solvent, and the cleaning after the secondary end capping is performed with a cleaning liquid containing an acid. The method described. 8. The method according to claim 6 or 7, characterized in that the organic solvent is methanol. 9. The acid is phosphoric acid,
The method according to any one of claims 6 to 8.