JP2664798B2 - Capillary column for gas chromatography and method for producing the same - Google Patents

Description

The present invention relates to a capillary column for gas chromatography,
In particular, the present invention relates to a capillary column using a nonpolar substance as a stationary phase and useful as a standard capillary column, and a method for producing the same.

[Conventional technology]

The capillary column for gas chromatography is obtained by subjecting the inner surface of a capillary made of styrene steel, quartz glass or the like to a surface inactivation treatment as necessary, and providing a layer such as polydimethylsiloxane or polyethylene glycol as a stationary phase. Capillary columns for gas chromatography, which are generally available on the market, use surface treatment and stationary phase formation methods,
Since the resolving property is slightly different due to the difference in conditions and the like, a standard capillary column is required. As a standard capillary column having a nonpolar stationary phase, a capillary column in which a stationary phase made of a nonpolar hydrocarbon, squalane, is provided on the inner surface of a stainless steel capillary is known.
Capillary columns with a squalane stationary phase are useful as standards for calibration of retention indices in gas chromatography. In particular, it is essential for the separation and analysis of hydrocarbons having a relatively small molecular weight.

Stationary phases such as polydimethylsiloxane and polyethylene glycol of a capillary column for gas chromatography are crosslinked with a peroxide such as dibenzoyl peroxide in order to improve the washing resistance. Crosslinking also improves the heat resistance of the stationary phase. As a method of cross-linking a hydrocarbon such as squalane, a method using a peroxide, a method of cross-linking by electron beam irradiation, and a silane water cross-linking are conventionally known. As for the method using a peroxide, a method of performing a high-temperature treatment after crosslinking in order to remove a decomposition product having a high boiling point and a large polarity is also known.

Capillary columns using quartz glass capillaries
It has higher resolution than columns using SUS stainless steel or multi-component glass capillaries and has the advantage that it can be applied to microanalysis.Trimethylsilane, octamethylcyclotetrasiloxane, hexamethyldisilazane are applied to the inner surface of quartz glass capillaries. Etc.
A stationary phase is provided.

[Problems to be solved by the invention]

As described above, a capillary column in which a stationary phase composed of squalane is provided on the inner surface of a stainless steel capillary is known, but it uses uncrosslinked squalane and has no heat resistance. In addition, high separation performance as in the case of using a quartz glass capillary cannot be obtained. In order to form a heat-resistant stationary phase using squalane, it is necessary to crosslink the squalane.

However, when squalane crosslinked by the conventional method as described above is used as a stationary phase of a capillary column for gas chromatography, there is a disadvantage that the separation characteristics are deteriorated in any case. In the method using a peroxide such as dicumyl peroxide, decomposition products having a high boiling point and a high polarity such as acetophenone and cumyl alcohol remain after crosslinking, so that tailing occurs in the detection of a polar substance. Even if a very small amount of the polar decomposition product remains in the stationary phase, it changes the retention ratio and retention index of the analyte. There is also a method of removing such decomposition products by high-temperature treatment, but due to the thermal decomposition of squalane having a branched structure, the separation characteristics are significantly different from those of uncrosslinked squalane, and the suitability as a standard column is lost. . Even by crosslinking by electron beam irradiation, if a substance having a polar group such as trimethylolpropane trimethacrylate or triaryl isocyanurate, which is conventionally known as a crosslinking aid for polyethylene, which is a typical nonpolar polymer, is added to squalane, By combining these with squalane, the nonpolarity characteristic of squalane is lost. In the case of silane water cross-linking, in addition to mixing the silane compound and the catalyst, the separation characteristics are different from those of the uncross-linked squalane,
Loses suitability as a standard column. Thus, heretofore, there has been no method of crosslinking squalane suitable for use as the stationary phase of a capillary column for gas chromatography. Under these circumstances, conventional commercially available capillary columns for gas chromatography using squalane as a stationary phase are those in which the squalane liquid phase is not crosslinked, and the maximum operating temperature is only 90 to 95 ° C, and the high boiling point is high. Cannot be used for component analysis.

On the other hand, it was difficult to uniformly form the squalane stationary phase on the inner surface of the quartz glass capillary regardless of the presence or absence of crosslinking. This is because squalane is a non-polar substance having poor reactivity and poor wettability with quartz glass having some polarity, so that it is difficult to form a uniform coating on the inner surface of the quartz capillary.

Therefore, an object of the present invention is to realize a capillary column for gas chromatography having a stationary phase comprising squalane and having a heat resistance, and a method for producing the same.

Further, an object of the present invention is to use a cross-linked squalane as a stationary phase, which does not cause tailing in the detection of a polar substance due to cross-linking, and does not involve the decomposition of squalane and a change in separation characteristics due to mixing of a cross-linking agent or a catalyst. An object of the present invention is to realize a capillary column and a method for producing the same.

Another object of the present invention is to realize a capillary column for gas chromatography having a uniform stationary phase composed of cross-linked squalane on the inner surface of a quartz glass capillary, and a method for producing the same.

[Means for solving the problem]

In the present invention, in order to realize a gas chromatography capillary column having a heat-resistant stationary phase composed of squalane and a method for producing the same, a stationary phase composed of cross-linked squalane is provided on the inner surface of the capillary. It is preferable to use ionizing radiation for crosslinking squalane.

Further, the present invention provides a capillary column using cross-linked squalane as a stationary phase and a method for producing the same, which do not cause tailing in the detection of a polar substance, do not decompose squalane by crosslinking, and do not change the separation characteristics due to mixing of a cross-linking agent or a catalyst. In order to realize, on the inner surface of a capillary such as quartz glass,
A stationary phase formed by adding an aliphatic unsaturated hydrocarbon having no polar group as a crosslinking assistant and crosslinking squalane by irradiation with ionizing radiation was provided.

In the present invention, in order to further realize a capillary column for gas chromatography having a uniform stationary phase composed of cross-linked squalane on the inner surface of a quartz glass capillary and a method for producing the same, the inner surface of the quartz glass capillary is treated with atoms or silanol groups capable of reacting with silanol groups. The surface was treated with a silane compound having an atomic group and two or more alkyl groups, and a uniform stationary phase composed of cross-linked squalane was provided thereon.

As ionizing radiation for crosslinking squalane,
Electron beam, X-ray, γ-ray, α-ray, etc. can be used,
Use of X-rays is simple. The radiation dose is chosen so that sufficient crosslinking takes place. Depending on the presence and amount of the crosslinking aid, 1 × 10 ³ to 1 × 10 ⁵ Gy (1 × 10 ⁵ rad to 1 × 10 ⁵ Gy)
A range of ⁷ rad) is appropriate. Especially 5 × 10 ³ to 5 × 10 ⁴
Gy (5 × 10 ⁵ rad to 5 × 10 ⁶ rad) is preferred. 1 × 10
^When a radiation dose exceeding ⁵ Gy is used, squalane is decomposed and the decomposition product becomes a polar stationary phase due to a polar substance generated by a reaction with oxygen in the air. This decomposition product remains in the stationary phase even after baking through an inert gas such as helium gas.

In order to cross-link squalane without causing tailing in the detection of polar substances and without causing degradation of squalane due to cross-linking or change in separation characteristics due to the incorporation of a cross-linking agent or catalyst, non-polar cross-linking assistants to squalane alone or squalane After the stationary phase to which the agent has been added is formed, ionizing radiation is applied. Especially when using electron beams as ionizing radiation,
It is preferable to use a non-polar crosslinking assistant. As the nonpolar crosslinking aid, an aliphatic unsaturated hydrocarbon having no polar group is preferable. The aliphatic unsaturated hydrocarbon may have a carbon-carbon double bond or may have a carbon-carbon triple bond. Specific examples are shown below.

1-tetradecene, 1-hexadecene, 1-aicocene, 2,5-dimethyl-2,4-hexadiene, 1,13-tetradecadiene, 1,11-dodecadiene, squalene.

The aliphatic unsaturated hydrocarbon may be an oligomer having an unsaturated bond, such as 1,2-polybutadiene and 1,4-polybutadiene.

The amount of the crosslinking aid added to squalane varies depending on the type of the crosslinking aid and irradiation conditions such as electron beam,
Usually, a range of 0.5 to 10 parts by weight per 100 parts by weight of squalane is suitable. The addition amount is selected so that sufficient cross-linking occurs, but squalane does not decompose, and the separation characteristics do not change due to the cross-linking aid. Since both squalane and the crosslinking aid are hydrocarbons, they are compatible and can be uniformly mixed.

In order to improve the thermal stability of the stationary phase, an oxide inhibitor may be added within a range that does not affect the separation characteristics.

To form the stationary phase, squalane or a mixture of squalane and a crosslinking assistant is diluted with an appropriate organic solvent, filled into a capillary, and attached to the inner surface of the capillary as a thin layer by a dynamic or static method, and then ionized. Irradiate radiation. Stainless steel may be used as the capillary, but a quartz glass capillary is preferred for obtaining high resolution. When using a quartz glass capillary,
Prior to forming the squalane stationary phase, the capillary is surface treated as described below.

The quartz glass capillary is preferably formed of high-purity quartz, and particularly preferably a high-purity quartz used for an optical fiber. It is preferable to provide a heat-resistant protective layer such as polyimide on the outer surface of the quartz glass capillary.

The silane compound having an atom or an atomic group capable of reacting with a silanol group and at least two alkyl groups, which is used for inactivating the inner surface of the quartz glass capillary, is preferably represented by the following structural formula.

In the formula, R ₁ , R ₂ , and R ₃ may be the same or different, R ₁ and R ₂ represent an alkyl group, and R ₃ represents an alkyl group or a hydrogen atom. R ₄
Represents an atom or an atomic group capable of replacing a hydrogen atom of a silanol group ≡SiOH present on the glass surface.

A compound in which at least one of R ₁ , R ₂ and R ₃ represents an alkyl group having 2 or more carbon atoms is preferred, and a compound in which all of R ₁ , R ₂ and R ₃ represent an alkyl group is particularly preferred. 2 carbon atoms
The above alkyl group is, for example, an ethyl group, an n-propyl group,
An isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and an n-hexyl group. The alkyl group may have 7 or more carbon atoms.

R ₄ is an atom or an atomic group capable of replacing active hydrogen such as a silanol group, for example, a halogen atom, an alkoxy group,
It is a hydrogen atom. Specific examples include a chlorine atom, a bromine atom, a fluorine atom, a methoxy group, an ethoxy group, and a hydrogen atom.

Specific examples of the silane compound having two or more alkyl groups are as follows.

Trimethylchlorosilane, ethyldimethylchlorosilane, n-propyldimethylchlorosilane, isopropyldimethylchlorosilane, di-n-butylmethylchlorosilane, n-butyldimethylchlorosilane, isobutyldimethylchlorosilane, t-butyldimethylchlorosilane, di-t-butylmethylchlorosilane, n -Pentyldimethylchlorosilane, n-hexyldimethylchlorosilane, n-decylmethylchlorosilane, cetyldimethylchlorosilane, 1,2-dimethylpropyldimethylchlorosilane, n-octadecyldimethylchlorosilane, trimethylbromosilane, trimethylfluorosilane, trimethylmethoxysilane, trimethylethoxy Silane, triethylethoxysilane, trimethyl-n-propoxysilane, n-octadecyl Methyl methoxy silane, di -
t-butylmethylsilane, tri-n-propylsilane,
Triisopropylsilane.

In order to perform the capillary inactivation treatment, the silane compound itself or a solution is filled in a capillary and attached to the inner surface of the capillary by a dynamic method or a static method. Heat, if necessary, to promote the reaction with the silanol groups.

[Action]

In the present invention, by using crosslinked squalane as the stationary phase, the stationary phase composed of squalane has heat resistance. In particular, heat resistance is improved by irradiating a predetermined radiation dose of ionizing radiation to crosslink squalane. Furthermore, by adding an aliphatic unsaturated hydrocarbon having no polar group to squalane as a cross-linking aid and irradiating with ionizing radiation to cross-link and form a stationary phase, excellent separation characteristics can be obtained. That is, tailing does not occur in the detection of polar substances due to crosslinking,
In addition, there is no change in separation characteristics due to decomposition of squalane by heat or an electron beam, mixing of a silane compound or a catalyst, and the like. Further, by using squalane crosslinked by such a method as a stationary phase, particularly excellent heat resistance can be obtained.

Further, the inner surface of the quartz glass capillary was deactivated with a silane compound having an atom or an atomic group capable of substituting the hydrogen atom of the silanol group ≡SiOH and two or more alkyl groups. It is sufficiently depolarized, and a stationary phase composed of squalane can be formed uniformly. As will be shown later in Comparative Examples, the surface treatment with a silane compound outside the present invention does not sufficiently perform this effect.

 Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1] Fig. 1 shows an example of a quartz capillary column according to the present invention. A surface treatment layer 2 made of a silane compound is applied to the inner surface of a quartz capillary 1 and a stationary phase 3 made of cross-linked squalane is provided. A polyimide protective film 4 is provided on the outer surface.

This quartz capillary column was manufactured as follows. First, an anhydrous synthetic quartz glass tube was softened by a drawing furnace at a temperature of about 2000 ° C., and was drawn into a quartz capillary having an inner diameter of 0.32 mm and an outer diameter of 0.45 mm. Immediately after stretching, the outer surface of the quartz capillary 1 was coated with a polyimide varnish (DuPont PyreML), passed through an electric furnace at a temperature of 500 ° C., dried and cured to a thickness of about 10 μm.
A μm polyimide protective film 4 was formed. The quartz capillary 1 covered with the polyimide protective film 4 is cut into a length of 30 m, and a thin film of a silane compound is formed on the inner surface of the capillary 1 by a dynamic method using a 35% solution of n-octadecyldimethylchlorosilane in methylene chloride. I let it. After heating to 250 ° C. to sufficiently react the OH group on the inner surface of the quartz glass with the silane compound, methylene chloride was passed through the quartz capillary 1 to remove excess silane compound. Thus, the surface treatment layer 2 of the silane compound was applied to the inner surface of the capillary 1. 0 in squalane n-pentane.
A 26% by weight solution was filled into the silane-treated quartz capillary. The solvent was removed by a static method to form an uncrosslinked stationary phase having a thickness of 0.30 μm. After sufficiently purging with helium gas, the entire capillary column was irradiated with X-rays at a radiation dose of 2 × 10 ⁴ Gy (2 Mrad) to crosslink the squalane. Purging with helium gas was performed again to obtain stationary phase 3.

The capillary column thus obtained was mounted on a gas chromatography apparatus and used at the column temperature of 110 ° C. to analyze a standard sample in which nine substances were dissolved. As a result, excellent separation characteristics as shown in FIG. 2 were obtained. Was done.

After completing this analysis, the column was heated at 120 ° C. for 50 hours, and gas chromatography of the same sample was performed again at the same column temperature (110 ° C.). FIG. 3 shows the results. 120
Even after heating at 50 ° C for 50 hours, good separation characteristics were exhibited. this is,
It means that the column has good heat resistance.

Further, FIG. 4 shows that n- to heating time at 120 ° C.
The transition of the retention ratio k of dodecane and the number of theoretical plates n (stages / m) are shown. The retention ratio k and the theoretical plate number n were almost constant.

In addition, gas chromatography of commercial gasoline was performed using a new capillary column. The column temperature was increased from 40 ° C to 120 ° C at a rate of 2 ° C per minute. The result is the fifth
As shown in the figure, good separation characteristics were obtained.

Example 2 A quartz capillary 1 was manufactured in the same manner as in Example 1, covered with a polyimide protective film 4, and subjected to silane treatment.

A mixture of 100 parts by weight of squalane and 3 parts by weight of squalene was diluted 380-fold (weight ratio) with n-pentane and filled into a silane-treated quartz capillary. The solvent was removed by a static method to form a 0.25 μm thick layer (uncrosslinked stationary phase). A dose of 5 Mrad throughout the capillary column
The squalane was cross-linked by irradiating with the above electron beam to obtain a stationary phase 3.

The thus obtained capillary column was mounted on a gas chromatography apparatus, and was used for gasoline analysis at a column temperature of 40 to 120 ° C. As a result, excellent separation characteristics similar to those of Example 1 were obtained.

Example 3 Instead of the 35% solution of n-octadecyldimethylchlorosilane used in Example 2, an inner surface treatment of the capillary was performed using a 50% solution of n-octadecyldimethylmethoxysilane in methylene chloride, and squalane was used to form a stationary phase. A mixture of 100 parts by weight and 5 parts by weight of 1-hexadecene was used to irradiate an electron beam at a dose of 1 × 10 ⁵ Gy (10 Mrad) for crosslinking of squalane. Otherwise in the same manner as in Example 2, a capillary column using crosslinked squalane as a stationary phase was obtained.

The separation characteristics when used for gas chromatography of gasoline were the same as in Example 2.

Example 4 The inner surface of the capillary was treated using the same 35% solution of n-octadecyldimethylchlorosilane as used in Example 2, and 100 parts by weight of squalane and 3 parts by weight of 1,13-tetradecadiene were used to form a stationary phase. Parts of the mixture were used. Otherwise in the same manner as in Example 2, a capillary column using crosslinked squalane as a stationary phase was obtained.

The separation characteristics when used for gas chromatography of gasoline were the same as in Example 2.

[Example 5] Instead of the 35% solution of n-octadecyldimethylchlorosilane used in Example 2, the inner surface of the capillary was treated with a 20% solution of n-dodecyldimethylchlorosilane in methylene chloride, and squalane 100 was used to form a stationary phase. Parts by weight and 1,2
A mixture of 3 parts by weight of polybutadiene oligomer was used. Otherwise, in the same manner as in Example 2, a capillary column using crosslinked squalane as a stationary phase was obtained.

The separation characteristics when used for gas chromatography of gasoline were the same as in Example 2.

The effects of the present invention will be further clarified by showing comparative examples below.

Comparative Example 1 A capillary column was manufactured in the same manner as in Example 1 except that the X-ray irradiation was omitted.

As in the capillary column of Example 1, the column temperature was 110
When gas chromatography of the standard sample was performed at ℃,
The bleaching phenomenon probably caused by the evaporation of the squalane liquid phase was large, and it was almost impossible to separate components.

Comparative Example 2 A capillary column was manufactured in the same manner as in Example 1 except that the radiation dose of X-ray irradiation was set to 8 × 10 ² Gy.

As in the case of the capillary column of Example 1, when a standard sample was subjected to gas chromatography, the operating temperature of the column was limited to about 95 ° C., which was not much different from the uncrosslinked column.

Comparative Example 3 In Example 2, electron beam irradiation of the uncrosslinked stationary phase was omitted.

The initial separation characteristics when used in gas chromatography of gasoline were the same as in Example 2.

[Comparative Example 4] In Example 2, the surface treatment of the inner surface of the capillary was omitted, and the other conditions were the same as in Example 2.

When used in gas chromatography of gasoline, the separation peak was broad and the separation characteristics were poor.

[Comparative Example 5] Instead of the 35% solution of n-octadecyldimethylchlorosilane used in Example 2, an inner surface treatment of the capillary was performed using a 25% solution of octamethylcyclotetrasiloxane (the solvent was methylene chloride). Otherwise in the same manner as in Example 2, a capillary column using crosslinked squalane as a stationary phase was obtained.

When used for gas chromatography of gasoline, the separation peak was broad, though not as good as in Comparative Example 4, and the separation characteristics were inferior to those of Example 2. The surface treatment with the silane compound outside the present invention shows that the separation characteristics are inferior to those of the capillary column of the present invention.

〔The invention's effect〕

According to the present invention, a capillary column for gas chromatography having squalane, which is a non-polar hydrocarbon, having a heat resistance and having a stationary phase is realized. Also according to the present invention,
A gas chromatography capillary column having cross-linked squalane as a stationary phase having heat resistance and excellent separation performance is realized. That is, the capillary column according to the present invention has excellent heat resistance, and the maximum use temperature in gas chromatography is 110 to 120 ° C. Moreover, despite the fact that squalane is cross-linked, tailing in the detection of polar substances caused by large polar decomposition products, such as in the case of using peroxide for cross-linking, or in the case of silane water cross-linking In addition, there is no change in separation characteristics due to mixing of a crosslinking agent or a catalyst. Further, there is no change in separation characteristics due to decomposition of squalane as in the case of a method of crosslinking using a peroxide and removing decomposition products by high-temperature treatment.

Further, according to the present invention, it is possible to realize a capillary column for gas chromatography in which a stationary phase composed of cross-linked squalane is uniformly formed on the inner surface of a quartz glass capillary.

The capillary column for gas chromatography of the present invention is particularly useful as a standard capillary column having a non-polar stationary phase. Separation of lower aliphatic hydrocarbons, m-
It is also applicable to separation of xylene and p-xylene.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a capillary column for gas chromatography according to the present invention, FIG. 2 is a gas chromatograph obtained in one embodiment of the present invention, and FIG. 3 is a capillary column of the same embodiment. Gas chromatograph after heating at 120 ° C. for 5 hours, FIG. 4 is a graph showing the change in the retention ratio and the number of theoretical plates during heating the capillary column of the same example at 120 ° C., and FIG. 5 is another graph obtained in the same example. It is a gas chromatograph. DESCRIPTION OF SYMBOLS 1 ... Quartz capillary 2 ... Surface treatment 3 ... Stationary phase 4 ... Polyimide protective film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Okano 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Inside the Electric Wire Research Laboratory, Hitachi Cable Co., Ltd. No. Hitachi Naka Seiki Co., Ltd. (72) Inventor Masami Maeda 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Hidaka Works Co., Ltd. (56) References JP-A-56-51661 JP, A) JP-A-57-91452 (JP, A) JP-A-50-120399 (JP, A) JP-A-62-153756 (JP, A) JP-A-57-141554 (JP, A) 63-210768 (JP, A)

Claims (8)

(57) [Claims] 1. A capillary column for gas chromatography, comprising a stationary phase composed of cross-linked squalane on the inner surface of a capillary. 2. The gas chromatography capillary column according to claim 1, wherein said stationary phase is composed of squalane cross-linked by a predetermined radiation dose of ionizing radiation. 3. The capillary column for gas chromatography according to claim 1, wherein said capillary is a quartz glass capillary. 4. The gas chromatography capillary column according to claim 3, wherein the quartz glass capillary has an inner surface subjected to silylation treatment. 5. The capillary column for gas chromatography according to claim 3, wherein the quartz glass capillary has a heat-resistant outer surface coated and a silylation inner surface. 6. An inner surface of a quartz glass capillary is subjected to silylation treatment using a silane compound having an atom or an atomic group capable of reacting with a silanol group and two or more alkyl groups, and an inner surface layer made of squalane is formed on the inner surface. Providing a method for producing a capillary column for gas chromatography, wherein the inner surface layer is crosslinked. 7. The method for producing a capillary column for gas chromatography according to claim 6, wherein said crosslinking is carried out by irradiation with ionizing radiation of 1 × 10 ³ to 1 × 10 ⁵ Gy. 8. An inner surface of a quartz glass capillary is subjected to a silylation treatment using a silane compound having an atom or an atomic group capable of reacting with a silanol group and two or more alkyl groups, and squalane and a polar group are formed on the inner surface. A method for producing a capillary column for gas chromatography, comprising: providing an inner surface layer made of an aliphatic unsaturated hydrocarbon having no inner surface; and cross-linking the inner surface layer by irradiation with ionizing radiation.