JP2007047156A - Quantitative determination method by chromatography of trace constituent, and sampling unit for solid phase micro extraction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantitative determination method by chromatography of a trace constituent capable of easily and accurately determining quantity of the trace constituent with bad sensitivity to chromatography, and a sampling unit for solid phase micro extraction (SPME) used for this quantitative determination method. <P>SOLUTION: The method of determining the quantity of the trace constituent by chromatography comprises a first process of vaporizing a silylation agent and making fiber of the sampling unit for SPME adsorb it, a second process of vaporizing the trace constituent and making the fiber adsorb it, a third process of silylating the trace constituent on the fiber or in the gas phase vaporized from the fiber, and a fourth process of determining the quantity of the trace constituent by chromatography. A needle for SPME performs the first process. The sequence of the first process and the second process may be changed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for quantifying trace components by chromatography and a sampling unit for solid-phase microextraction used in such a method.

In recent years, emulsion polymerization in which a monomer is dispersed in water and radical polymerization is performed using a water-soluble initiator has become the mainstream as a polymer production method. In such emulsion polymerization, there may be a problem whether the reaction is completely completed, that is, there is no residual component that generates an unpleasant odor or the like. Since components such as unpleasant odors can be perceived by humans at the ppb level, it is necessary to establish a trace analysis method. As means for quantifying such trace components, gas chromatography, high performance liquid chromatography and the like are known.
By the way, for example, (meth) acrylic acid or the like containing a carboxy group has poor sensitivity to gas chromatography. Therefore, in order to quantify a trace component of (meth) acrylic acid, it is necessary to prepare a sample in advance. However, the conventional sample preparation methods have a problem that a large amount of sample, a large amount of organic solvent, and the like are required, and the operation is complicated and requires a lot of time.

  In order to solve this problem, a sample extraction / concentration / introduction preparation method for chromatographic analysis called a solid phase microextraction (SPME) method has been developed in recent years. The SPME sampling unit has a first end, a syringe barrel having a second end, a plunger slidable within the syringe barrel, and a plunger extending from the first end of the syringe barrel. It has a syringe and a fiber extending from the second end of the syringe barrel and surrounded by a SPME needle. An adsorbent is immobilized on the surface of the fiber, and the vaporized sample can be adsorbed here. The SPME needle passes a septum of a sample vial or a gas chromatography vaporization chamber septum while protecting a built-in fiber. By pushing the plunger, the fiber is exposed from the SPME needle and adsorbs the vaporized sample.

  A method for performing gas chromatography analysis using such an SPME sampling unit will be described. First, a septum-equipped vial containing a trace component is appropriately heated to vaporize the trace component to be quantified. A SPME needle is passed through a vial with a septum containing a trace amount component in a state where the fiber is stored. The plunger is pushed down to expose the fiber in the gas phase and adsorb the sample onto the fiber. Return the plunger and place the fiber in the SPME needle. Pull the SPME needle out of the vial. Next, the SPME needle is passed through the gas chromatography septum while the fiber is housed. The plunger is pushed down, the fiber is exposed in the vaporization chamber, and the sample is thermally desorbed and the column is transferred.

However, even when the SPME method is used, the concentration is still insufficient for quantifying trace components that are insensitive to gas chromatography, such as (meth) acrylic acid.
Therefore, an object of the present invention is to provide a method for quantifying a trace component by chromatography, which can easily and accurately quantify a trace component having low sensitivity to chromatography.
Moreover, an object of this invention is to provide the sampling unit for SPME used for this fixed_quantity | assay method.

As a result of intensive studies to solve the above problems, the present inventors have focused on silylation of trace components. Many of the components in the sample can be analyzed by gas chromatography as they are, but in many cases, the hardly volatile components in the sample cannot be analyzed by gas chromatography. In particular, (meth) acrylic acid or the like having a carboxy group is likely to cause tailing, so that separation from not only the component but also adjacent components is not sufficient, and the accuracy of quantification is reduced. In this case, a symmetrical sharp peak can be drawn by changing to a silylated form with an appropriate silylating agent. Further, in gas chromatography, a thermally unstable compound cannot be analyzed as it is, but it can often be quantified by changing it to an appropriate silylated compound.
However, since silylation is generally carried out in a solution, the trace component concentrated to some extent by the SPME method is diluted again in a large amount of solvent and cannot be used for quantitative determination of the trace component. In addition, trimethylsilylated compounds are considered to be unsuitable for analysis of trace components during polymer production by emulsion polymerization because they are relatively unstable when containing a compound having water or a hydroxyl group.

  Therefore, as a result of further studies, the present inventors adsorbed the silylating agent on the fiber that adsorbs the gas of the SPME sampling unit, and reacted the trace component adsorbed on the fiber with the fiber. It is possible to easily and accurately quantify trace components that are insensitive to chromatography by using a silylated product or by heating it to the subsequent column transfer step to form a silylated product. The headline and the present invention were completed.

That is, the first invention of the present invention is a method for quantifying a trace component by chromatography, wherein a first step of adsorbing the vaporized trace component on a fiber of a sampling unit for SPME using the SPME method, silyl A second step of vaporizing the agent and adsorbing it on the fiber, a third step of silylating the trace component in the vapor phase vaporized on or from the fiber, and a fourth step of quantifying the trace component by chromatography. The present invention provides a method for quantifying a trace component by chromatography, characterized in that it has a component.
The second invention of the present invention is a method for quantifying a trace component by chromatography, wherein the silylating agent is vaporized and adsorbed on a fiber of a sampling unit for SPME, and the trace component is vaporized. A second step of adsorbing the fiber on the fiber, a third step of silylating the trace component in a gas phase vaporized on or from the fiber, and a fourth step of quantifying the trace component by chromatography. The present invention provides a method for quantitative determination of trace components by chromatography.
According to a third aspect of the present invention, there is provided a syringe barrel having a first end, a second end, and a plunger slidable inside the syringe barrel, wherein the plunger is a first barrel of the syringe barrel. A syringe having a handle extending from one end and a fiber extending from the second end of the syringe barrel, the periphery of which is protected by an SPME needle, for quantifying trace components by chromatography A sampling unit for SPME, wherein the fiber adsorbs a vaporized silylating agent.

  By using the method of the present invention, trace components having low sensitivity to chromatography can be quantified easily and accurately. Moreover, if the SPME sampling unit of this invention is used, the said fixed_quantity | quantitative_assay can be performed easily.

1 and 2 are schematic views of an embodiment of the SPME sampling unit according to the third aspect of the present invention. FIG. 1 shows a state in which the fiber is stored, and FIG. 2 shows a state in which the fiber is exposed.
The SPME sampling unit 1 includes an SPME holder (i) and a fiber assembly (ii). The SPME sampling unit 1 extracts and concentrates a sample with an extraction phase fixed to the fiber 2. The SPME needle 3 is for penetrating a septum of a sample vial or a gas chromatography vaporization chamber septum while protecting the built-in fiber 2. By pushing the plunger 4, the fiber 2 is exposed from the SPME needle 3, and extraction and desorption are performed. The SPME holder (i) is a holder for attaching the fiber assembly (ii) inside. Can be used repeatedly. In the fiber assembly (ii), a wire 5 having a fiber 2 to which a liquid phase and an adsorbent used for extraction are fixed is attached to the tip of the fiber assembly (ii). The wire 5 has a spring and is linked to the plunger 4.

The adsorption of the silylating agent to the fiber can be performed, for example, as follows. A silylating agent is added to a vial with a septum and the silylating agent is vaporized by heating at room temperature or at room temperature. The SPME needle containing the fiber is passed through this. The plunger is pushed down to expose the fiber in the vial, and the silylating agent is adsorbed onto the fiber for a predetermined time (extraction). The plunger is then returned to house the fiber in the SPME needle. Pull the SPME needle out of the vial.
Thereby, the sampling unit for SPME by which the silylating agent was adsorbed is obtained.
Such a sampling unit for SPME is particularly useful when a trace component such as (meth) acrylic acid contained in an aqueous system such as an emulsion having low sensitivity to gas chromatography is quantified using gas chromatography.
Examples of (meth) acrylic acid include acrylic acid and methacrylic acid.

The most common silylation reaction is trimethylsilylation, and the trimethylsilylating agent reacts with active protons under mild conditions to form a trimethylsilylated product.
Examples of the silylating agent include hexamethyldisilazane (HMDS), N, O-bis (trimethylsilyl) acetamide (BSA), N, O-bis (trimethylsilyl) trifluoroacetamide (BSTFA), N-trimethylsilylimidazole (TSIM). ), Trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, tert-butyldimethylsilyl chloride, ethyldimethylsilylimidazole, n-propyldimethylsilylimidazole, trifluoropropyldimethylsilylimidazole, heptafluoropentyldimethylsilylimidazole and the like. Among these, BSA and BSTFA are preferable in that they have strong trimethylsilylation ability. Furthermore, BSTFA is particularly preferable because it is highly volatile and can be easily adsorbed onto the fiber.

The SPME sampling unit of the third invention of the present invention is useful for the implementation of the second invention of the present invention.
In the second invention of the present invention, the silylating agent is vaporized and the silylating agent is adsorbed to the SPME sampling unit as the first step, but the SPME sampling unit of the third invention of the present invention is used. In this case, the first step can be omitted.
In the second step of the second invention of the present invention, a trace component is vaporized and adsorbed on the fiber. Adsorption of trace components onto the fiber can be performed, for example, as follows. A sample containing a trace component to be quantified is added to a vial with a septum and heated to vaporize the trace component. When the sample is an emulsion polymer (emulsion) after the production of the polymer by emulsion polymerization or the like, it is possible to add the same amount or less of water to the emulsion from the viewpoint of performing quantification using an extrapolation method. preferable. The vial is then heated to vaporize the trace components. When the trace component to be quantified is, for example, (meth) acrylic acid, the heating condition is preferably 80 to 100 ° C. for 10 minutes to 4 hours, particularly preferably 85 to 95 ° C. for 1 to 3 hours. A SPME needle is passed through a vial with a septum in which a trace component has been vaporized while the fiber is housed. The plunger is then pushed down to expose the fiber in the vial and adsorb the vaporized trace components onto the fiber. Here, a trace component and a silylating agent are adsorbed on the fiber. The plunger is then returned to house the fiber in the SPME needle. Pull the SPME needle out of the vial.

  In order to efficiently adsorb (extract) trace components to the fiber, (i) select a fiber that can provide a large distribution coefficient according to the characteristics such as polarity and boiling point of the trace component to be quantified, Select the film thickness. (Ii) The sample solubility of a trace component to be quantified is reduced by using means such as adding salt. (Iii) The pH of the sample is adjusted using acids such as hydrochloric acid and phosphoric acid, alkalis such as ammonia and sodium hydroxide, and the partition coefficient is improved. (Iv) Make the space volume in the vial as small as possible. (V) Forced stirring using a magnetic stirrer or the like to promote the movement of the substance. It is preferable to take measures such as.

In the third step of the second invention of the present invention, the trace component is silylated on the fiber or in the vapor phase vaporized from the fiber. Silylation on the fiber means that the inside of the vial is heated to a temperature at which the silylation reaction takes place, and the trace component adsorbed on the fiber reacts with the silylating agent. In this case, the fiber is housed in the needle, and the silylation reaction is performed before the needle is pulled out of the vial. In the case of gas chromatography, for example, in the case of gas chromatography, the silylation is performed by allowing the SPME needle to pass through the gas chromatography injection tank (vaporization chamber) while storing the fiber in which the trace component and the silylating agent are adsorbed. The plunger is pushed down to expose the fiber in the injection tank, and the adsorbed trace component and the silylating agent are vaporized and reacted to silylate the trace component. At this time, the inside of the injection tank is kept at a temperature at which the silylation reaction proceeds.
The fourth step of the second invention of the present invention is a step of quantifying trace components using chromatography and can be quantified according to a conventional method.
In this way, when a solvent is used, a trace component adsorbed on a fiber (solid phase) by the SPME method and a silylating agent are silylated on the fiber (solid phase) or on the gas phase vaporized from the fiber. Unlike trace components, since trace components are not diluted, even a trace component with low sensitivity to chromatography can be quantified.

  1st invention of this invention changes the order of the 1st process and 2nd process of 2nd invention. That is, in the first step of the first invention of the present invention, the trace component is adsorbed on the fiber, and in the second step, the silylating agent is adsorbed on the fiber. The other steps are the same as in the second invention of the present invention.

The present invention is particularly effective for analysis of a compound having low sensitivity to analysis of chromatography, particularly gas chromatography, such as (meth) acrylic acid contained in an aqueous system such as an emulsion.
EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example. Unless otherwise specified, “%” represents mass% and “part” represents mass part.

(Manufacture of acrylic polymer emulsion)
75 parts of deionized water was placed in a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, and the temperature was raised to 80 ° C. while blowing nitrogen. Under stirring, 0.02 part of potassium persulfate was added, and then a monomer mixture consisting of 40 parts of butyl acrylate, 58 parts of methyl methacrylate and 2 parts of methacrylic acid was added to Latemul E-118B (manufactured by Kao Corporation: effective Component 25%) A part (3 parts) of a monomer pre-emulsion (referred to the monomer mixture emulsified with the monomer mixture, emulsifier and water) added with 8 parts and deionized water 15 parts. The polymerization was performed for 30 minutes while maintaining the temperature in the reaction vessel at 80 ° C. Subsequently, while maintaining the temperature in the reaction vessel at 80 ° C., the remaining monomer pre-emulsion (120 parts) and 30 parts of an aqueous solution of potassium persulfate (active ingredient 0.5%) were separately added using a separate dropping funnel. The polymerization was carried out dropwise over 180 minutes while maintaining the temperature in the reaction vessel at 80 ° C. After completion of dropping, the mixture was stirred at the same temperature for 120 minutes to obtain an acrylic polymer emulsion of the present invention.

Quantitative determination of methacrylic acid according to the first aspect of the present invention The gas chromatography / mass spectrometer (GC / MS) is GC-MS QP5050 manufactured by Shimadzu Corporation, and the GC column is InertCap5MS / Sil manufactured by GL Sciences (length 30 m, inner diameter 0). .25 mm, film thickness 1.0 μm). The GC temperature condition was 60 ° C. (1 min) −10 ° C./min-300° C. The GC inlet temperature was 280 ° C., the carrier gas was helium, the column flow rate was 1.2 mL / min, and the measurement was performed by the split method (split ratio 1:10). The interface temperature of the mass spectrometer was 250 ° C. As the SPME set, a SPME unit manufactured by Spelco and a vial with Teflon (registered trademark) / silicone (17 mL) were used. As the fiber for SPME, Carboxen / PDMS and a film thickness of 75 μm were used. BSTFA was used as the trimethylsilylating agent.

1 g of the acrylic polymer emulsion and 1 g of water were added to a vial, sealed tightly and mixed well, and then heated in an oven at 90 ° C. for 2 hours to vaporize components containing methacrylic acid.
An SPME needle was passed through the vial with the fiber contained therein. The plunger was then pushed down to expose the fiber in the vial for 10 minutes, allowing the vaporized components to adsorb onto the fiber (extraction). Next, the plunger was returned to store the fiber in the SPME needle, and the SPME needle was pulled out from the vial. Next, 2 μl of BSTFA was added to a vial different from the above and evaporated at room temperature. An SPME needle containing a fiber having adsorbed vaporized components was passed through the vial. The plunger was pushed down and the fiber was exposed in the vial for 2 minutes to adsorb BSTFA to the fiber (extraction). Next, the plunger was returned to store the fiber in the SPME needle, and the SPME needle was pulled out from the vial. At this point, the fiber has adsorbed the vaporized component and the silylating agent, but has not yet reacted. Next, an SPME needle was inserted into the gas chromatography inlet, and GC / MS analysis was performed. The inlet temperature of 280 ° C. is a temperature at which methacrylic acid and BSTFA react to silylate methacrylic acid. GC / MS analysis was performed 3 times under the same conditions.

  When extraction is performed by the SPME method, the measured value varies depending on the coexisting substances. Accordingly, a methacrylic acid aqueous solution having a known concentration was added to the emulsion, and a quantitative value was obtained by extrapolation. 1 g of an aqueous methacrylic acid solution (3 types of 25 ppm, 50 ppm, and 100 ppm) was added to 1 g of the emulsion, heated and adsorbed (extracted) under the same conditions as described above, the peak area was measured, and a calibration curve was prepared. Three calibration curves were created under the same conditions. FIG. 3 shows the three calibration curves obtained. The calibration curves all showed good linearity, and it was confirmed that quantitative analysis according to the present invention was possible. Table 1 shows the quantitative values and reproducibility of methacrylic acid obtained by extrapolation from the obtained three calibration curves. The amount of residual methacrylic acid in the sample emulsion was 26 ppm, and the sensitivity was increased about 10 times compared to the case where it was quantified before silylation. The reproducibility was also good.

  In Example 1, methacrylic acid was quantified in the same manner as in Example 1 except that DFD was used instead of BSTFA. Compared with the case of quantification before silylation, the sensitivity was increased about 3 times. The reproducibility was also good.

(Comparative Example 1)
Gas chromatography / mass spectrometer (GC / MS) is GC-MS QP5050 manufactured by Shimadzu Corporation, and GC column is DB-WAX (length 30 m, inner diameter 0.25 mm, film thickness 0.25 μm) manufactured by J & W Scientific. Using. The GC temperature condition was 100 ° C. (1 min) −10 ° C./min−250° C. (5 min). The GC inlet temperature was 250 ° C., the carrier gas was helium, the column flow rate was 1.3 mL / min, and the measurement was performed by the split method (split ratio 1:10). The interface temperature of the mass spectrometer was 250 ° C.
0.3 g of the same emulsion as in Example 1 was placed in a centrifuge tube (10 mL), and acetone was added to make up to 5 mL. This was stirred well and sonicated for 10 minutes to precipitate the resin. Thereafter, 1 μl of the supernatant was injected into GC / MS. As the GC column, DB-WAX manufactured by J & W Scientific Co., which is a polar column, was used in order to suppress tailing of methacrylic acid. No silylation was performed. Others were the same as in Example 1.

  The quantitative value was 28 ppm which almost coincided with the case of Example 1. However, since a large amount of solvent was added, trace analysis as in Example 1 is impossible, and the 10 ppm level is the limit of quantification. Moreover, since it is necessary to extract methacrylic acid completely, acetone which is a polar solvent was used as an extraction solvent. For this reason, a large amount of water, which is the solvent of the emulsion, is also extracted into acetone, and silylation is difficult.

(Comparative Example 2)
Adsorption of the vaporized component using the SPME method was performed in the same manner as in Example 1. Thereafter, the fiber on which the vaporized component was adsorbed was dispersed in a solution in which 5 μl of BSTFA was dissolved in 0.5 mL and stirred at 160 ° C. for 5 minutes. Thereafter, quantification was performed in the same manner as in Example 1.

  In Comparative Example 2, since silylation was performed in the liquid, the vaporized component adsorbed on the fiber was diluted, and the sensitivity by gas chromatography was very poor.

(Test Example 1)
The following treatment was performed on the emulsion when methacrylic acid was adsorbed on the fiber using a 100 ppm aqueous solution of methacrylic acid. (I) untreated (pH 4.3), (ii) stirring at 300 rpm, (iii) adding phosphoric acid to adjust pH to 2.2, (iv) adding saturated amount of NaCl, (v) stirring at 300 rpm While adding phosphoric acid, the pH was adjusted to 2.2. (Vi) While stirring at 300 rpm, phosphoric acid was added to adjust the pH to 2.2, and a saturated amount of NaCl was added. After the above treatment, the amount of methacrylic acid extracted was measured. The results are shown in FIG.

  As is clear from FIG. 4, when the treatments (ii) to (vi) were performed, the extraction amount of methacrylic acid increased as compared to the untreated ((i)). In particular, (vi) increased more than 10 times. From this result, it is considered that the trace component at the ppb level can be detected by the method of the present invention.

  The present invention can be used in the field of microanalysis by chromatography.

It is the schematic of one Embodiment of the SPME sampling unit of 3rd invention of this invention, Comprising: The state in which the fiber was accommodated is shown. It is the schematic of one Embodiment of the SPME sampling unit of 3rd invention of this invention, Comprising: The state which the fiber exposed is shown. 2 is a diagram showing a calibration curve for silylation of methacrylic acid in Example 1. FIG. In Experiment 1, it is a figure which shows the extraction amount of methacrylic acid at the time of performing each process.

Explanation of symbols

1 SPME sampling unit 2 Fiber 3 SPME needle 4 Plunger 5 Wire

Claims (6)

A method for quantifying trace components by chromatography, comprising:
A first step of adsorbing the vaporized trace component on a fiber of a sampling unit for SPME using a solid phase microextraction (SPME) method;
A second step of vaporizing the silylating agent and adsorbing it on the fiber;
A third step of silylating the trace component in the vapor phase vaporized from or from the fiber;
A fourth step of quantifying the trace component by chromatography;
A method for quantifying a trace component by chromatography, characterized by comprising: A method for quantifying trace components by chromatography, comprising:
A first step of vaporizing a silylating agent and adsorbing it on a fiber of a sampling unit for solid phase microextraction (SPME);
A second step of vaporizing the trace component and adsorbing it on the fiber;
A third step of silylating the trace component in the vapor phase vaporized from or from the fiber;
A fourth step of quantifying the trace component by chromatography;
A method for quantifying a trace component by chromatography, characterized by comprising:   The method for quantifying a trace component by chromatography according to claim 1 or 2, wherein the trace component is (meth) acrylic acid.   The method for quantifying a trace component by chromatography according to any one of claims 1 to 3, wherein the chromatography is gas chromatography. A syringe having a first end, a syringe barrel having a second end, a plunger slidable within the syringe barrel, the plunger having a handle extending from the first end of the syringe barrel ,
And a solid phase microextraction (SPME) sampling unit having a fiber extending from the second end of the syringe barrel and surrounded by a SPME needle and quantifying trace components by chromatography,
The SPME sampling unit, wherein the fiber adsorbs the vaporized silylating agent. The SPME sampling unit according to claim 5, wherein the chromatography is gas chromatography.

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