Method and system for analyzing volatile organic compounds

Abstract

To provide an analysis method for a volatile organic compound that can quantitatively and simply separate a volatile organic compound in a water sample to perform quantitative analysis with high accuracy.SOLUTION: An analysis method for a volatile organic compound includes the steps of: causing a sample containing a plurality of types of volatile organic compounds to flow into a collection column 4 together with a first mobile phase 1 to collect the volatile organic compounds in the collection column 4; causing a second mobile phase 2 containing a water-soluble organic solvent to circulate in the collection column 4 to cause the volatile organic compounds to flow out from the collection column 4; causing the volatile organic compounds to flow into a separation column 12 to separate the volatile organic compounds; and detecting the separated volatile organic compounds. The collection column 4 is filled, as a filler, with hydrophobic porous fine particles having a number of pores with a gas phase fixed to the inside thereof, and the first mobile phase 1 is an inorganic salt solution containing inorganic salt in an amount of 0.5 mol / L or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for analyzing volatile organic compounds and an analysis system used therefor. [Background technology]

[0002] Known methods for quantitatively analyzing organic compounds in water samples include gas chromatography (GC) and high performance liquid chromatography (HPLC). When attempting to quantitatively analyze trace amounts of organic compounds in groundwater and other water samples using these methods, it is necessary to extract the organic compounds from the water sample and concentrate them to a certain amount before analyzing them in order to improve analytical accuracy. In other words, in order to improve analytical accuracy, it is necessary to repeatedly carry out a predetermined pretreatment process. For this reason, there has been a demand for a method that can quantitatively analyze organic compounds in water samples with high accuracy using simpler operations.

[0003] As a technique for analyzing organic compounds in water samples with simpler operations, for example, a liquid chromatograph column packed with hydrophobic porous microparticles having a large number of pores in which a gas phase (gas) is immobilized, capable of selectively collecting hydrophobic compounds, and a method for analyzing hydrophobic compounds using the column have been proposed (Non-Patent Documents 1 and 2). Furthermore, a method has been proposed in which volatile organic compounds (VOCs) such as benzene and toluene in a water sample are collected and concentrated in the columns proposed in Non-Patent Documents 1 and 2, and then introduced into a general reversed phase (RP) column for separation and analysis (Non-Patent Document 3). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Analytical Chemistry, 2015, 87, p.1180-1187 [Non-Patent Document 2] The Journal of Physical Chemistry C, 2018, 122, p.4409-4418 [Non-Patent Document 3] Abstracts of the 67th Annual Meeting of the Japan Society for Analytical Chemistry (2018) "H1004 HPLC Analysis of Volatile Organic Compounds in Water Samples Using Preconcentration by Surface Bubble Modulation Liquid Chromatography" Summary of the Invention [Problem to be solved by the invention]

[0005] According to the method proposed in Non-Patent Document 3, it was possible to quantitatively analyze volatile organic compounds such as benzene and toluene in water samples with high accuracy. However, among volatile organic compounds, it is difficult to quantitatively analyze halogenated hydrocarbons such as dichloromethane, chloroform, and dichloroethane with high accuracy, and there is room for further improvement.

[0006] The present invention has been made in consideration of the problems of the conventional techniques, and an object of the present invention is to provide a method for analyzing volatile organic compounds that can quantitatively and easily separate volatile organic compounds in a water sample and quantitatively analyze them with high accuracy. Another object of the present invention is to provide an analysis system for use in the method for analyzing volatile organic compounds. [Means for solving the problem]

[0007] That is, according to the present invention, there is provided a method for analyzing volatile organic compounds as shown below. [1] A method for analyzing volatile organic compounds, comprising the steps of: flowing a sample containing multiple types of volatile organic compounds together with a first mobile phase into a collection column for liquid chromatography to collect the volatile organic compounds in the collection column; flowing a second mobile phase containing a water-soluble organic solvent through the collection column that has collected the volatile organic compounds to cause the volatile organic compounds to flow out from the collection column; flowing the volatile organic compounds that have flowed out from the collection column into a separation column for liquid chromatography to separate the volatile organic compounds; and detecting the separated volatile organic compounds, wherein the collection column is filled with hydrophobic porous microparticles having a large number of pores in which a gas phase is fixed, as a filler, and the first mobile phase is an aqueous salt solution containing 0.5 mol / L or more of salts. [2] The method for analyzing volatile organic compounds according to [1] above, further comprising the steps of introducing a third mobile phase containing water into the collection column from which the volatile organic compounds have been discharged, and regenerating the collection column by heating to 55°C or higher or by introducing an inert gas. [3] The method for analyzing volatile organic compounds according to [1] above, further comprising the step of regenerating the collection column from which the volatile organic compounds have been discharged by introducing an inert gas into the collection column. [4] The porous microparticles are silica-based fillers having chemically modified groups on their surfaces; The method for analyzing a volatile organic compound according to any one of the above [1] to [3], wherein the chemical modifying group is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 50 carbon atoms, in which a hydrogen atom may be substituted with a cyano group, a hydroxyl group, a carboxy group, an acid amide group, an imide group, a sulfonic acid group, an amino group, a glyceroid group, a halogen atom, or an aryl group. [5] The method for analyzing volatile organic compounds according to any one of [1] to [4], wherein the porous microparticles are at least one type of silica-based filler selected from the group consisting of octadecyl group-bonded silica gel, octyl group-bonded silica gel, butyl group-bonded silica gel, triacontyl group-bonded silica gel, phenylhexyl group-bonded silica gel, and phenyl group-bonded silica gel. [6] The method for analyzing a volatile organic compound according to any one of [1] to [5], wherein the pores of the porous microparticles have an average pore diameter of 3 to 30 nm, and the porous microparticles have an average particle diameter of 1 to 50 μm. [7] The method for analyzing a volatile organic compound according to any one of [1] to [6], wherein the salt is at least one selected from the group consisting of sodium phosphate, sodium sulfate, ammonium sulfate, calcium chloride, magnesium chloride, ammonium formate, and ammonium acetate.

[0008] Furthermore, according to the present invention, there is provided an analytical system for volatile organic compounds as described below. [8] A system for analyzing volatile organic compounds, comprising: a first mobile phase which is an aqueous salt solution containing 0.5 mol / L or more of salts; a second mobile phase which contains a water-soluble organic solvent; a collection column and a separation column for liquid chromatography; a first pressurizing mechanism which causes a sample containing multiple types of volatile organic compounds to flow into the collection column together with the first mobile phase; a second pressurizing mechanism which causes the second mobile phase to flow through the collection column which has collected the volatile organic compounds, thereby causing the volatile organic compounds to flow out of the collection column and causing the flowed-out volatile organic compounds to flow into the separation column; and a detection unit which detects the volatile organic compounds separated in the separation column, wherein the collection column is filled with hydrophobic porous microparticles having a large number of pores in which a gas phase is immobilized. [9] The volatile organic compound analysis system according to [8], further comprising a regeneration mechanism for regenerating the collection column from which the volatile organic compounds have been discharged, the regeneration mechanism including a third mobile phase containing water, a third pressurization mechanism for introducing the third mobile phase into the collection column from which the volatile organic compounds have been discharged, and a heating mechanism for heating the collection column to 55°C or higher, or an inert gas introduction mechanism for introducing an inert gas into the collection column.

[10] The volatile organic compound analysis system according to [8], further comprising a regeneration mechanism for regenerating the collection column from which the volatile organic compounds have flowed out, the regeneration mechanism having an inert gas introduction mechanism for introducing an inert gas into the collection column from which the volatile organic compounds have flowed out. Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for analyzing volatile organic compounds, which is capable of quantitatively and simply separating volatile organic compounds in a water sample and quantitatively analyzing them with high accuracy, and also to provide an analysis system used in the method for analyzing volatile organic compounds. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of an analysis system for volatile organic compounds of the present invention. [Diagram 2] 1 is a chromatogram showing the results of Analysis Example 1. [Figure 3A] 1 is a chromatogram showing the results of Analysis Example 2. [Figure 3B] FIG. 3B is a partially enlarged view of FIG. 3A. [Figure 4] 1 is a chromatogram showing the results of VOC analysis in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Analysis method for volatile organic compounds> Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The present inventors have studied the reason why it is difficult to perform a highly accurate quantitative analysis of halogenated hydrocarbons such as dichloromethane, chloroform, and dichloroethane in the method proposed in Non-Patent Document 3. As a result, they have found that halogenated hydrocarbons are more soluble in water (have high water solubility) than non-halogenated volatile organic compounds such as benzene, toluene, and xylene, and that because of their relatively high water solubility, they are not sufficiently collected in a collection column packed with hydrophobic porous microparticles having a large number of pores in which a gas phase (gas) is fixed.

[0012] As a result of further investigation, the inventors discovered that by using an aqueous salt solution containing a predetermined concentration or more of salts as the mobile phase used when introducing a water sample containing volatile organic compounds into a collection column, halogen-based volatile organic compounds which have relatively high water solubility can be efficiently collected in the collection column, thereby arriving at the present invention.

[0013] That is, the method for analyzing volatile organic compounds of the present invention (hereinafter, also simply referred to as "analysis method") includes a step of collecting volatile organic compounds in a collection column (collection step), a step of discharging volatile organic compounds from the collection column (discharge step), a step of separating volatile organic compounds (separation step), and a step of detecting volatile organic compounds (detection step). The collection step is a step of flowing a sample containing multiple volatile organic compounds together with a first mobile phase into a collection column for liquid chromatography, and collecting the volatile organic compounds in the collection column. This collection column is filled with hydrophobic porous microparticles having a large number of pores in which a gas phase is fixed, as a filler. The first mobile phase is an aqueous salt solution containing 0.5 mol / L or more of salts. Hereinafter, the details of the method for analyzing volatile organic compounds of the present invention will be described.

[0014] (Collection process) In the collection step, a sample containing a plurality of volatile organic compounds is introduced into a collection column for liquid chromatography together with a first mobile phase. This allows the volatile organic compounds to be collected in the collection column. The sample to be analyzed can be a water sample containing water as the main component. Specific examples of water samples can be river and lake water, seawater, groundwater, industrial wastewater, etc. Examples of volatile organic compounds can be non-halogenated organic compounds such as benzene, toluene, and xylene; halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and chloroform; and organic compounds such as various pharmaceuticals and pesticides. In the analysis method of the present invention, both non-halogenated organic compounds such as benzene, which have relatively low water solubility, and halogenated hydrocarbons such as dichloromethane, which have relatively high water solubility, can be analyzed with high accuracy. In particular, the analysis method of the present invention can accurately quantify even halogenated organic compounds that are more soluble in water than non-halogenated organic compounds such as benzene, so it is preferable to analyze a water sample containing non-halogenated organic compounds. In particular, the analytical method of the present invention is useful as a method for analyzing water samples containing volatile organic compounds having a solubility in water at 25°C of 2 g / L or more, preferably 3 g / L or more, and more preferably 5 g / L or more.

[0015] The collection column is packed with hydrophobic porous particles having a large number of pores in which a gas phase is immobilized. This collection column is a so-called "Surface Bubble Modulation Liquid Chromatography (SBMLC) column" (hereinafter also referred to as "SBMLC column"), and is disclosed in Non-Patent Documents 1 to 3, etc. SBMLC In the column, the interface area between the mobile phase, such as water, and the hydrophobic porous microparticles is extremely small, so that hydrophilic compounds having hydrophilic functional groups are not substantially retained. In contrast, volatile hydrophobic compounds are distributed into the chemically modified base layer on the surface of the porous microparticles through the immobilized gas phase, so SBMLC It is efficiently retained in the column.

[0016] SBMLCAs the porous fine particles packed in the column, a silica-based packing material having a chemically modified group on its surface can be used. Examples of the chemically modified group bonded to the surface of this silica-based packing material include an alkyl group having 1 to 50 carbon atoms and an aryl group having 6 to 50 carbon atoms. In these alkyl groups and aryl groups, the hydrogen atom may be substituted with a cyano group, a hydroxyl group, a carboxy group, an acid amide group, an imide group, a sulfonic acid group, an amino group, a glyceroid group, a halogen atom, or an aryl group.

[0017] The porous microparticles are silica-based fillers such as octadecyl-bonded silica gel, octyl-bonded silica gel, butyl-bonded silica gel, triacontyl-bonded silica gel, phenylhexyl-bonded silica gel, and phenyl-bonded silica gel.

[0018] Among them, the chemical modifying group is preferably an octadecylsilyl (ODS) group. SBMLC The porous microparticles packed in the column are preferably porous spherical silica gel whose surface is chemically modified with an ODS group. The average pore size of the pores in the porous microparticles is preferably 3 to 30 nm, more preferably 4 to 10 nm. The average particle size of the porous microparticles is preferably 1 to 50 μm, more preferably 5 to 40 μm.

[0019] The first mobile phase (eluent) is an aqueous salt solution containing 0.5 mol / L or more of salts. By flowing a sample containing a plurality of kinds of volatile organic compounds into the collection column together with the first mobile phase, it is possible to separate hydrophobic volatile organic compounds from hydrophilic compounds while substantially collecting only the volatile organic compounds in the collection column. Furthermore, by using an aqueous salt solution containing salts at a predetermined concentration or more as the first mobile phase, it is possible to efficiently collect halogenated hydrocarbons, which have been difficult to collect so far and have a higher water solubility than non-halogenated organic compounds such as benzene, toluene, and xylene, in the collection column. From the viewpoint of further improving the collection rate of halogenated hydrocarbons in the collection column, the content of salts in the aqueous salt solution used as the first mobile phase is preferably 0.75 mol / L or more, and more preferably 0.9 mol / L or more. There is no particular limit to the upper limit of the content of salts in the aqueous salt solution, and it may be, for example, 3 mol / L or less.

[0020] As the salts, various organic salts can be used in addition to inorganic salts such as alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and alkali metal phosphates. Examples of alkali metals include lithium, sodium, and potassium. Examples of alkaline earth metals include magnesium, calcium, strontium, and barium. Examples of halogens contained in alkali metal halides and alkaline earth metal halides include chlorine, bromine, and iodine. Among them, the salts preferably include sodium phosphate, sodium sulfate, ammonium sulfate, calcium chloride, magnesium chloride, ammonium formate, and ammonium acetate. These salts can be used alone or in combination of two or more.

[0021] In addition, as the salt, a salt constituting a buffer solution used in general reverse phase column chromatography can be used. That is, a buffer solution can be used as the first mobile phase. Examples of the buffer solution include a phosphate buffer solution and a citrate buffer solution.

[0022] The collection column (SBMLC column) can be prepared, for example, by the following method. First, a volatile organic solvent is passed through a column packed with porous microparticles such as porous spherical silica gel whose surface is chemically modified with ODS groups, and the voids in the column are filled with the organic solvent. Next, the plugs on both ends of the column are removed, and the column is placed in an oven and heated to about 70°C to dry. The column is then attached to an analysis system, and pure water is passed through the column while appropriately controlling the pressure and flow rate, thereby forming a collection column (SBMLC column) in which the gas phase is immobilized in the pores of the porous microparticles.

[0023] Alternatively, an SBMLC column can be prepared by a method similar to the method for regenerating a collection column described later. That is, a column packed with porous microparticles is filled with a first mobile phase or a solvent such as water by pressurizing the column, and then the pressurization is stopped. The column is then heated to 55° C. or higher to form a collection column (SBMLC column) in which a gas phase is immobilized in the pores of the porous microparticles.

[0024] (Outflow process) In the outflow step, a second mobile phase containing a water-soluble organic solvent is passed through the collection column that has collected the volatile organic compounds. This allows the volatile organic compounds to be outflowed from the collection column. As the water-soluble organic solvent used in the second mobile phase (eluent), a typical water-soluble organic solvent used in reversed-phase column chromatography can be used. Examples of such water-soluble organic solvents include acetonitrile, methanol, ethanol, and tetrahydrofuran. Among these, acetonitrile is preferred.

[0025] As the second mobile phase, a mixed solvent of a water-soluble organic solvent and water is usually used. The ratio of the water-soluble organic solvent to water in the mixed solvent may be appropriately set. Specifically, it can be arbitrarily set within the range of water-soluble organic solvent:water (volume ratio)=10:90 to 90:10, preferably within the range of water-soluble organic solvent:water (volume ratio)=20:80 to 80:20.

[0026] (separation process) In the separation step, the volatile organic compounds discharged from the collection column are made to flow into a separation column for liquid chromatography. This allows the volatile organic compounds to be separated. The separation column may be a column for liquid chromatography capable of separating a plurality of types of volatile organic compounds. However, in consideration of the fact that the volatile organic compounds are made to flow together with a second mobile phase containing a water-soluble organic solvent such as acetonitrile, it is preferable to use a column for reverse phase (RP) chromatography.

[0027] As described above, the second mobile phase flowing out from the collection column together with the volatile organic compounds may be used as an eluent when separating a plurality of types of volatile organic compounds in a separation column.

[0028] (Detection process) In the detection step, the volatile organic compounds separated in the separation column are detected. To detect the volatile organic compounds, a general detector used in high performance liquid chromatography can be used. Examples of the detector include a photodiode array detector, an ultraviolet-visible absorbance detector, a fluorescence detector, a differential curvature detector, an evaporative light scattering detector, and a mass spectrometer. The detector may be appropriately selected depending on the characteristics of the volatile organic compounds to be analyzed. By going through each of the above steps, the types and contents of multiple volatile organic compounds in a sample can be analyzed and measured.

[0029] (Regeneration process) The analytical method of the present invention preferably further comprises a step of introducing a third mobile phase containing water into the collection column from which the volatile organic compounds have been eluted, and regenerating the collection column by heating to 55° C. or higher or by introducing an inert gas (regeneration step). By providing such a regeneration step, the collection column can be returned to a state almost equal to that before analysis (the state before the volatile organic compounds were captured), so that it is not necessary to remove the collection column from the analysis system for regeneration every time analysis is performed, and continuous analysis is possible.

[0030] As the third mobile phase, an eluent containing water is used. Although it is preferable to use water as the third mobile phase, the first mobile phase used for collecting volatile organic compounds can also be used. To heat the collection column, a column oven or a thermostatic bath can be used. The collection column is heated to 55°C or higher, preferably 60°C or higher, and more preferably 65°C or higher. By heating to a predetermined temperature or higher while the third mobile phase containing water is introduced, the gas phase can be immobilized again in the pores of the porous microparticles packed in the collection column. In addition, the gas phase can be immobilized again in the pores of the porous microparticles packed in the collection column by further introducing an inert gas into the collection column after the introduction of the third mobile phase. As the inert gas, a dry inert gas such as nitrogen gas, dry air (pure air), argon gas, or helium gas can be used.

[0031] In addition, in the regeneration step, an inert gas may be introduced into the collection column from which the volatile organic compounds have flowed out to regenerate the collection column. In this way, the gas phase can be fixed again in the pores of the porous microparticles packed in the collection column by introducing the inert gas into the collection column. The temperature of the collection column when the inert gas is introduced may be, for example, 10 to 80°C.

[0032] <Analysis system for volatile organic compounds> Fig. 1 is a schematic diagram showing one embodiment of the volatile organic compound analysis system of the present invention (hereinafter, also simply referred to as "analysis system"). The volatile organic compound analysis system 100 of the embodiment shown in Fig. 1 is a system used in the above-mentioned volatile organic compound analysis method, and includes a first mobile phase 1, a second mobile phase 2, a collection column 4 and a separation column 12 for liquid chromatography, a first pressurizing mechanism and a second pressurizing mechanism such as pumps 8 and 18, and a detection unit such as a detector 10.

[0033] The first mobile phase 1 is pressurized and delivered by a pump 8. A sample containing multiple types of volatile organic compounds is introduced into the system through an injector 14, and flows into the collection column 4 together with the first mobile phase 1. As the sample flows into the collection column 4, the volatile organic compounds in the sample are collected in the collection column 4, and the components in the sample that are not collected flow out of the collection column 4 together with the first mobile phase 1 and move to the waste liquid 5.

[0034] After switching the six-way valve 20, the second mobile phase 2 pressurized by the pump 18 is made to flow into the collection column 4. This allows the collected volatile organic compounds to flow out of the collection column 4 and into the separation column 12. The volatile organic compounds are then separated in the separation column 12, and then flow out of the separation column 12 and introduced into the detector 10 for identification. The remaining eluent is then stored in the waste liquid 15.

[0035] The analysis system 100 of this embodiment further includes a regeneration mechanism for regenerating the collection column 4 from which the volatile organic compounds have been discharged. The regeneration mechanism includes a third pressurizing mechanism such as a pump 8 for introducing a third mobile phase 3 into the collection column 4, and a heating mechanism 6 for heating the collection column 4 to 55° C. or higher. As shown in FIG. 1, the pressurizing mechanism (pump 8) for pressurizing the third mobile phase 3 may also serve as the pressurizing mechanism (pump 8) for pressurizing the second mobile phase 2.

[0036] After the analysis, the collection column 4 can be regenerated using the regeneration mechanism according to the following procedure. First, the third mobile phase 3, such as water, is pressurized and pumped by the pump 8 to flow into the collection column 4. Then, the collection column 4 is heated to a predetermined temperature or higher by the heating mechanism 6. The temperature and time for heating the collection column 4 are determined based on the gas phase generation rate (F SBMLC The temperature dependence of the gas phase generation rate F(n=3) in the SBMLC column is shown in Table 1. The time dependence of the gas phase generation rate F(n=3) in the SBMLC column at 65°C is shown in Table 2.

[0037] TIFF0007627909000001.tif63170

[0038] TIFF0007627909000002.tif55170

[0039] As shown in Table 1, it can be seen that there is a significant difference in the gas phase production rate when the column temperature is set to 50°C and when it is set to 60°C. That is, in the regeneration step, the heating mechanism 6 heats the collection column 4 to 55°C or higher. Also, as shown in Table 2, it can be seen that the gas phase production rate reaches nearly equilibrium by heating for 3 minutes or more. The heating time of the collection column 4 can be appropriately set depending on the size (volume) of the collection column 4, etc.

[0040] Next, the collection column 4 is cooled to about room temperature (20 to 30° C.), and then a third mobile phase 3 such as water is passed through the collection column 4 until equilibrium is reached. This allows the gas phase to be immobilized again within the pores of the porous microparticles packed in the collection column 4, and the collection column 4 can be regenerated.

[0041] In addition, the regeneration mechanism preferably has an inert gas introduction mechanism for introducing an inert gas into the collection column after the third mobile phase has been introduced, instead of the above-mentioned heating mechanism. By introducing an inert gas into the collection column into which the third mobile phase has been introduced, the gas phase can be fixed again in the pores of the porous microparticles packed in the collection column.

[0042] Furthermore, it is also preferable that the regeneration mechanism has an inert gas introduction mechanism for introducing an inert gas into the collection column from which the volatile organic compounds have flowed out. In this manner, by introducing an inert gas into the collection column, the gas phase can be fixed again in the pores of the porous microparticles packed in the collection column.

[0043] According to the method for analyzing volatile organic compounds of the present invention carried out using the above-mentioned analysis system, as described above, volatile organic compounds in a water sample can be separated and quantitatively analyzed easily and with high accuracy without requiring special operations such as extraction and concentration. In addition, volatile organic compounds such as halogenated hydrocarbons, which are more soluble in water than non-halogenated volatile organic compounds such as benzene, toluene, and xylene, can be quantitatively analyzed with high accuracy through simple operations. EXAMPLES

[0044] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0045] <Collection column> A volatile organic solvent was passed through a column packed with octadecylsilyl-bonded silica gel (ODS) (product name "Cadenza 5CD-C18", manufactured by Intact, inner diameter 3.0 mm x length 30 mm), filling the space in the column with the organic solvent. Next, the plugs on both ends of the column were removed, and the column was placed in an oven and heated to about 70°C to dry. The column was then attached to an analysis system, and pure water was passed through the column while controlling the pressure and flow rate to bring it to equilibrium, making it a collection column (SBMLC column).

[0046] <Separation column> A column packed with octadecylsilyl group-bonded silica gel (ODS) (product name "L-column 2 ODS", Chemicals Evaluation and Research Institute, Inc., inner diameter 4.6 mm x length 150 mm) was prepared as a separation column.

[0047] <Measurement of retention volume of halogenated hydrocarbons> (Analysis example 1) Halogenated hydrocarbons (dichloromethane (CH 2 Cl 2 ), 1,2-dichloroethane (C 2 H 4 Cl 2) and sample water containing 10 ppm of chloroform (CHCl 3 )) was prepared. 5 μL of this sample water was injected into the system from an injector, and (i) 2 mol / L calcium chloride (CaCl 2 ) aqueous solution; and (ii) water; were each used as a mobile phase and introduced into a trapping column (SBMLC column), and the retention volume of the halogenated hydrocarbon in the trapping column was measured. The results are shown in Figure 2.

[0048] As shown in Figure 2, when the 2 mol / L CaCl 2 aqueous solution was used as the mobile phase, it can be seen that the retention volume of the halogenated hydrocarbon increased significantly compared to the case where water was used as the mobile phase.

[0049] (Analysis Example 2) The retention volume of the halogenated hydrocarbon in the trapping column was measured in the same manner as in Analysis Example 1 described above, except that (i) 1 mol / L phosphate buffer; (ii) 0.1 mol / L phosphate buffer; and (iii) 0.01 mol / L phosphate buffer; were each used as the mobile phase. The pH of the phosphate buffer used at 25 °C was 7.2 in each case. The results are shown in Figure 3A. Also, a partially enlarged view of Figure 3A is shown in Figure 3B.

[0050] As shown in Figures 3A and 3B, when 1 mol / L phosphate buffer was used as the mobile phase, it can be seen that the retention volume of the halogenated hydrocarbon increased significantly compared to the cases where other phosphate buffers or water were used as the mobile phase.

[0051] The results shown in Figures 2, 3A, and 3B (the difference in the retention volume of the halogenated hydrocarbon depending on the type of mobile phase (concentration of inorganic salt)) are summarized in Table 3.

[0052] TIFF0007627909000003.tif69170

[0053] <VOC Analysis> (Example 1) Using the above-mentioned collection column and separation column, an analysis system similar to that shown in Figure 1 was constructed. 2 The aqueous solution was used as the first mobile phase, a mixed solvent of acetonitrile: 0.01 mol / L phosphate buffer (pH 7.2) = 3:7 (mass ratio) was used as the second mobile phase, and water was used as the third mobile phase. 2 Cl 2 ), 1,2-dichloroethane (C 2 H 4 Cl 2 ), and chloroform (CHCl 3 2 mL of sample water containing 10 ppm of VOCs was introduced into the system from the injector, and the first mobile phase was allowed to flow into the collection column at a flow rate of 0.5 mL / min. Next, the six-way valve was switched to introduce the second mobile phase into the collection column, causing the VOCs to flow out and then into the separation column for analysis. The analysis results are shown in Figure 4. The measurement conditions for the separation column are as follows: ·Flow rate: 1.0mL / min ·Temperature: 30℃ Detection: UV (190 nm)

[0054] After 2.5 minutes, the six-way valve was returned to its original position, the third mobile phase was allowed to flow into the collection column, and the collection column was heated to 65° C. for 3 minutes using the heating mechanism. After the collection column was cooled to near room temperature, the third mobile phase was allowed to flow through the collection column until equilibrium was reached, and the collection column was regenerated. [Industrial Applicability]

[0055] The method for analyzing volatile organic compounds of the present invention can separate and quantitatively analyze even samples containing volatile organic compounds that are relatively soluble in water with high accuracy and in a simple manner, and is therefore useful as a method for analyzing water samples such as river water, groundwater, industrial wastewater, and other water samples containing various organic compounds such as volatile pharmaceuticals and pesticides. [Explanation of symbols]

[0056] 1: First mobile phase 2: Second mobile phase 3: The third mobile phase 4: Collection column 5,15: Waste liquid 6:Heating mechanism 8,18:Pump 10: Detector 12: Separation column 14: Injector 20: 6-way valve 100: Volatile organic compound analysis system

Claims

1. A step of flowing a sample containing a plurality of volatile organic compounds into a collection column for liquid chromatography together with a first mobile phase, thereby collecting the volatile organic compounds in the collection column; a step of flowing a second mobile phase containing a water-soluble organic solvent through the collection column in which the volatile organic compounds have been collected, thereby causing the volatile organic compounds to flow out of the collection column; A step of flowing the volatile organic compounds discharged from the collection column into a separation column for liquid chromatography to separate the volatile organic compounds; and detecting the separated volatile organic compounds; the collection column is filled with hydrophobic porous microparticles having a large number of pores in which a gas phase is immobilized, The method for analyzing volatile organic compounds, wherein the first mobile phase is an aqueous salt solution containing 0.9 mol / L or more of salt.

2. The method for analyzing volatile organic compounds according to claim 1, further comprising the steps of: introducing a third mobile phase containing water into the collection column from which the volatile organic compounds have been discharged; and regenerating the collection column by heating to 55°C or higher or by introducing an inert gas.

3. 2. The method for analyzing volatile organic compounds according to claim 1, further comprising the step of regenerating said collection column by introducing an inert gas into said collection column from which said volatile organic compounds have flowed out.

4. the porous microparticles are silica-based fillers having chemically modified groups on their surfaces, The method for analyzing a volatile organic compound according to any one of claims 1 to 3, wherein the chemically modifying group is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 50 carbon atoms, in which a hydrogen atom may be substituted with a cyano group, a hydroxyl group, a carboxy group, an acid amide group, an imide group, a sulfonic acid group, an amino group, a glyceroid group, a halogen atom, or an aryl group.

5. The method for analyzing a volatile organic compound according to any one of claims 1 to 4, wherein the porous microparticles are at least one type of silica-based filler selected from the group consisting of octadecyl group-bonded silica gel, octyl group-bonded silica gel, butyl group-bonded silica gel, triacontyl group-bonded silica gel, phenylhexyl group-bonded silica gel, and phenyl group-bonded silica gel.

6. the average pore diameter of the pores of the porous microparticles is 3 to 30 nm; The method for analyzing a volatile organic compound according to any one of claims 1 to 5, wherein the average particle size of the porous microparticles is 1 to 50 µm.

7. The method for analyzing a volatile organic compound according to any one of claims 1 to 6, wherein the salt is at least one selected from the group consisting of sodium phosphate, sodium sulfate, ammonium sulfate, calcium chloride, magnesium chloride, ammonium formate, and ammonium acetate.

8. a first mobile phase which is an aqueous salt solution containing 0.9 mol / L or more of a salt; a second mobile phase containing a water-soluble organic solvent; A collection column and a separation column for a liquid chromatograph; a first pressurizing mechanism for causing a sample containing a plurality of volatile organic compounds to flow into the collection column together with the first mobile phase; a second pressurizing mechanism that causes the second mobile phase to flow through the collection column that has collected the volatile organic compounds, thereby causing the volatile organic compounds to flow out of the collection column and causing the flowed out volatile organic compounds to flow into the separation column; and a detection unit for detecting the volatile organic compounds separated in the separation column, The collection column is filled with hydrophobic porous particles having a large number of pores in which a gas phase is immobilized, as a packing material.

9. A regeneration mechanism for regenerating the collection column from which the volatile organic compounds have been discharged is further provided, The regeneration mechanism comprises: a third mobile phase comprising water; and a third pressurizing mechanism for introducing the third mobile phase into the collection column from which the volatile organic compounds have flowed out; 9. The system for analyzing volatile organic compounds according to claim 8, further comprising: a heating mechanism for heating the collection column to 55° C. or higher; or an inert gas introducing mechanism for introducing an inert gas into the collection column.

10. A regeneration mechanism for regenerating the collection column from which the volatile organic compounds have been discharged is further provided, 9. The volatile organic compound analyzing system according to claim 8, wherein the regeneration mechanism has an inert gas introducing mechanism for introducing an inert gas into the collection column from which the volatile organic compounds have flowed out.

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