Gas chromatography analysis method

Abstract

The present invention has the objective of providing a gas chromatography analysis method capable of analyzing the purity of high-purity ethylene carbonate with high precision by gas chromatography analysis, and the above objective can be solved by a gas chromatography analysis method by split injection of ethylene carbonate, comprising: injecting the ethylene carbonate to be analyzed into a gas chromatography analysis device; vaporizing the injected ethylene carbonate within a single-taper liner that is not filled with wool; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it; and detecting the ethylene carbonate that has passed through the capillary column by a detector.

Description

Technology Field

[0001] The present invention relates to a gas chromatography analysis method. Background Technology

[0002] In recent years, attention on lithium-ion rechargeable batteries (LiBs) has increased significantly as they contribute to reducing the burden on the global environment, such as through energy conservation or resource conservation. Recently, the scope of application for LiBs has been continuously expanding, extending beyond batteries for mobile devices such as smartphones and tablets to include batteries for vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs), and even to batteries for power storage. A LiB is a rechargeable battery that performs charging and discharging by the movement of lithium ions between a positive electrode and a negative electrode, and it consists of four main materials: a positive electrode, a negative electrode, a separator, and an electrolyte. High-polarity ethylene carbonate has become a representative electrolyte solvent due to its specific advantage of stabilizing the carbon material of the negative electrode by forming a nanometer-order film on the surface of the negative electrode, in addition to dissolving and dissociating lithium salts at high concentrations. However, since impurities in ethylene carbonate may affect battery performance during the charge-discharge cycle of the battery, high-purity ethylene carbonate is used for electrolyte applications.

[0003] Various methods for measuring the heteroalcohol content in ethylene carbonate in lithium-ion battery electrolytes have been proposed in the field of lithium-ion battery manufacturing (e.g., Patent Document 1). Prior art literature

[0004] CN105319303A The problem to be solved

[0005] In the analysis of the purity of high-purity ethylene carbonate, it has become clear that impurities such as ethylene oxide (EO), ethylene glycol (EG), and diethylene glycol (DEG) are generated in amounts that cannot be ignored in terms of the precision of the measurement results due to the decomposition of ethylene carbonate within the gas chromatography analysis apparatus. Therefore, a method for analyzing ethylene carbonate with higher precision is required.

[0006] That is, the present invention aims to provide a gas chromatography analysis method capable of analyzing the purity of high-purity ethylene carbonate with high precision by gas chromatography analysis. means of solving the problem

[0007] The inventors, as a result of careful consideration to solve the aforementioned problem, discovered that in the gas chromatography analysis method of the split method, by introducing a sample into a capillary column using a single-taper liner that is not filled with wool, the purity of high-purity ethylene carbonate can be analyzed with high precision, and thus arrived at the present invention.

[0008] In addition, the inventors, as a result of careful consideration to solve the aforementioned problem, discovered that in the gas chromatography analysis method of the split method, the purity of high-purity ethylene carbonate can be analyzed with high precision by injecting molten ethylene carbonate into the gas chromatography analysis device, and thus arrived at the present invention.

[0009] That is, the present invention is as follows.

[0010] [1]

[0011] As a gas chromatographic analysis method by the split injection method of ethylene carbonate,

[0012] Injecting the ethylene carbonate to be analyzed into a gas chromatography analyzer,

[0013] Vaporizing the injected ethylene carbonate within a single-taper liner that is not filled with wool,

[0014] Introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it through,

[0015] Detecting the ethylene carbonate that has passed through the above capillary column by a detector

[0016] Gas chromatography analysis method including

[0017] [2]

[0018] As a gas chromatographic analysis method by the split injection method of ethylene carbonate,

[0019] Injecting molten ethylene carbonate of the subject of analysis into a gas chromatography analysis device,

[0020] Vaporizing the injected ethylene carbonate within the liner,

[0021] Introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it through,

[0022] Detecting the ethylene carbonate that has passed through the above capillary column by a detector

[0023] Gas chromatography analysis method including

[0024] [3]

[0025] The above liner is a single-taper liner that is not filled with wool, as described in [2] gas chromatography analysis method.

[0026] [4]

[0027] A gas chromatography analysis method described in any one of [1] to [3], wherein the moisture content of the ethylene carbonate to be analyzed is 100 ppm or less.

[0028] [5]

[0029] A gas chromatography analysis method described in any one of [1] to [4], wherein the purity of the ethylene carbonate to be analyzed is 99.5 mass% or higher.

[0030] [6]

[0031] A gas chromatography analysis method described in any one of [1] to [5], wherein the carrier gas pressure when injecting the ethylene carbonate to be analyzed into the gas chromatography analysis device is 1.5 to 30 times the normal pressure, and after injection, the carrier gas pressure is set to the normal pressure.

[0032] [7]

[0033] A gas chromatography analysis method described in any one of [1] to [6], further comprising taking the ethylene carbonate of the subject of analysis into a syringe for injection of a gas chromatograph under dry inert gas.

[0034] [8]

[0035] A gas chromatography analysis method described in any one of [1] to [6], further comprising placing the ethylene carbonate to be analyzed into a vial for an auto-injector of a gas chromatograph under dry inert gas and closing the cap.

[0036] [9]

[0037] A gas chromatography analysis method described in any one of [1] to [8], further comprising sampling the ethylene carbonate of the subject of analysis under dry air, under dry inert gas, or under vacuum.

[0038]

[10]

[0039] A gas chromatography analysis method described in any one of [1] to [9], wherein the liquid phase in the above capillary column comprises at least one component selected from the group consisting of polysiloxane substituted with cyanopropyl and phenyl, polysiloxane substituted with cyanopropyl and methyl, polysiloxane substituted with trifluoropropyl, polysiloxane substituted with phenyl, and polyethylene glycol.

[0040]

[11]

[0041] A gas chromatography analysis method described in any one of [1] to

[10] , wherein the inlet temperature of the gas chromatography analysis device is 250 to 290°C.

[0042]

[12]

[0043] A gas chromatography analysis method described in any one of [1] to

[11] , wherein the detector temperature of the gas chromatography analysis device is 240 to 300°C.

[0044]

[13]

[0045] A gas chromatography analysis method described in any one of [1] to

[12] , wherein the inert gas circulated within the capillary column is nitrogen or helium.

[0046]

[14]

[0047] A gas chromatography analysis method as described in any one of [1] to

[13] , wherein the split ratio (inert gas flow rate discharged outside the capillary column: inert gas flow rate introduced into the capillary column) is 5:1 to 50:1. Effects of the invention

[0048] According to the present invention, a gas chromatography analysis method can be provided that can analyze the purity of high-purity ethylene carbonate with high precision by gas chromatography analysis. Brief explanation of the drawing

[0049] Figure 1 shows a schematic diagram of a gas chromatography analysis device (1). Figure 2 is a schematic diagram showing an example of a single taper liner. Specific details for implementing the invention

[0050] Hereinafter, embodiments for carrying out the present invention (hereinafter also referred to as "present embodiments") will be described in detail. Furthermore, the present invention is not limited to the present embodiments described below, and may be implemented with various modifications within the scope of its gist.

[0051] The gas chromatography analysis method according to the present embodiment is,

[0052] As a gas chromatographic analysis method by the split injection method of ethylene carbonate,

[0053] Injecting the ethylene carbonate to be analyzed into a gas chromatography analyzer,

[0054] Vaporizing the injected ethylene carbonate within a single-taper liner that is not filled with wool,

[0055] Introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it through,

[0056] Detecting the ethylene carbonate that has passed through the above capillary column by a detector

[0057] Includes

[0058] By including the above-described configuration, according to the present embodiment, the purity of high-purity ethylene carbonate can be analyzed with high precision by gas chromatography analysis.

[0059] In gas chromatography analysis, when separating with a capillary column, it is common practice to apply the split method, in which the injected sample is vaporized, but the entire amount is not introduced into the capillary column; instead, only an appropriate amount of sample matching the column's capacity is introduced, and the remainder is exhausted from a vent along with an inert gas. In the split method, the use of a wool-filled liner is a standard practice. This is because it offers the advantage of efficiently vaporizing the sample and enabling analysis with good reproducibility. Therefore, the inventors also initially used a wool-filled liner for split method analysis in the gas chromatography analysis of high-purity ethylene carbonate for electrolyte use, but measurement precision regarding purity and impurity concentration was not achieved. Furthermore, other liners for split method analysis and wool-filled liners for splitless method analysis were attempted, but reproducibility regarding purity and impurity concentration was not achieved. The inventors hypothesized that although it is generally accepted that split-less liners, which are not filled with wool, are not used in split-method analysis because reproducibility tends to be poor, thermal decomposition or hydrolysis of ethylene carbonate may easily occur on the surface of the wool intended to facilitate efficient vaporization. Therefore, they examined liners not filled with wool and discovered a single-taper liner for split-less analysis as a liner shape with good reproducibility of analysis values. It is surprising that, in the context of split-method analysis, a split-less liner is selected, which, according to common sense, would worsen the reproducibility of the analysis. One embodiment of the present invention is characterized by the use of a single-taper liner not filled with wool in the gas chromatographic analysis of high-purity ethylene carbonate.

[0060] The gas chromatography analysis method according to the present embodiment is,

[0061] As a gas chromatographic analysis method by the split injection method of ethylene carbonate,

[0062] Injecting molten ethylene carbonate of the subject of analysis into a gas chromatography analysis device,

[0063] Vaporizing the injected ethylene carbonate within the liner,

[0064] Introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it through,

[0065] Detecting the ethylene carbonate that has passed through the above capillary column by a detector

[0066] Includes

[0067] By including the above-described configuration, according to the present embodiment, the purity of high-purity ethylene carbonate can be analyzed with high precision by gas chromatography analysis.

[0068] The gas chromatography analysis according to the present embodiment includes introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows. That is, the gas chromatography analysis according to the present embodiment is an analysis by the split injection method. The split injection method enables reproducible analysis by allowing the analysis sample to vaporize within a liner while maintaining the concentration ratio of the sample components, and introducing a portion thereof into the capillary column. Within the liner, the liquid of the sample can simultaneously vaporize components with different boiling points and introduce them into the capillary column while maintaining the concentration ratio of the sample components.

[0069] However, this is not the case with solid ethylene carbonate at room temperature. When ethylene carbonate is injected into a gas chromatograph, phase transitions such as melting and vaporization occur, but the inventors suspected that due to the endothermic phenomenon caused by the enthalpy of fusion, vaporization is inhibited, making thermal decomposition or hydrolysis more likely to occur than vaporization. Therefore, by introducing molten ethylene carbonate into a gas chromatography analysis device, the inventors were able to simultaneously vaporize components with different boiling points within the liner, thereby preventing thermal decomposition or hydrolysis and increasing the precision of the gas chromatography analysis method.

[0070] In the above-described embodiment, it is suitable to simultaneously inject molten ethylene carbonate into a gas chromatography analysis apparatus and vaporize the ethylene carbonate within a single-taper injection liner that is not filled with wool. By performing these steps simultaneously, vaporization within the liner is facilitated by introducing molten ethylene carbonate, and furthermore, there is no adhesion to the wool within the liner, and vaporization within the liner is carried out smoothly. Therefore, according to the analysis method, a synergistic effect is achieved through the above-described features, and a superior precision of the gas chromatography analysis method is obtained.

[0071] Hereinafter, the gas chromatography analysis device (1) used in this embodiment will be described.

[0072] FIG. 1 shows a schematic diagram of a gas chromatography analysis device (1). The gas chromatography analysis device (1) is equipped with an injection part (11), a liner (12), an injection housing (14), a capillary column (20), and a detector (30).

[0073] The injection part (11) is equipped with a septum, although not shown, and is configured to allow a sample to be injected through the septum by a microsyringe.

[0074] The liner (12) is preferably a single-taper injection liner that is not filled with wool. By using the liner, the purity of high-purity ethylene carbonate can be analyzed with high precision. Specifically, as the liner (12), it is preferable to use the single-taper liner shown in FIG. 2. The material of the liner may be either quartz or glass, provided that it is deactivated. Even if the material is not quartz or glass, it can be used if it is deactivated so that the high-purity ethylene carbonate for the electrolyte and the impurities contained therein do not become activated and react within the liner.

[0075] Wool is a type of wool used in gas chromatography analysis, such as glass wool.

[0076] Single taper means having a configuration with a single taper structure.

[0077] The injection housing (14) secures the liner (12) inside by means of an O-ring (141). The injection housing (14) is provided with an inert gas introduction section (142). The inert gas introduced from the inert gas introduction section (142) passes through the liner (12), some of it is introduced into the capillary column, and the rest is exhausted from the inert gas outlet section (143) provided in the injection housing (14).

[0078] The capillary column (20) is preferably a capillary column having a polar liquid phase. The liquid phase in the capillary column (20) preferably comprises at least one component selected from the group consisting of polysiloxane substituted with cyanopropyl and phenyl, polysiloxane substituted with cyanopropyl and methyl, polysiloxane substituted with trifluoropropyl, polysiloxane substituted with phenyl, and polyethylene glycol, in order to increase the separation ability of impurities contained in ethylene carbonate. Among these, a combination of polysiloxane substituted with cyanopropyl and phenyl and dimethylsiloxane is preferred.

[0079] If the column length, column bore diameter, and liquid phase thickness can be verified as the separation and quantification of peaks in the actual chromatogram, the column length, column bore diameter, and liquid phase thickness can be selected from the commercially available lineup.

[0080] The detector (30) is not particularly limited to detectors used for gas chromatography analysis, but may include a hydrogen flame ionization detector (FID), a mass spectrometer (MS), a micro thermal conductivity detector (μTCD), etc.

[0081] Next, the gas chromatography analysis method according to the present embodiment will be described by way of an example using the gas chromatography analysis device (1).

[0082] Ethylene carbonate is injected into a gas chromatography analysis device (1). Ethylene carbonate is injected from an injection port (11). Subsequently, the injected ethylene carbonate is introduced into a liner (12) and vaporized within the liner (12). A portion of the vaporized ethylene carbonate is introduced into a capillary column (20) through which an inert gas flows and passes through. After passing through the capillary column (20), the ethylene carbonate is detected by a detector (30).

[0083] It is preferable that the ethylene carbonate injected into the gas chromatography analysis device (1) be in a molten state. By injecting molten ethylene carbonate, components with different boiling points within the liner can be vaporized simultaneously, thereby preventing thermal decomposition or hydrolysis and increasing the precision of the gas chromatography analysis method.

[0084] The temperature of the molten ethylene carbonate is preferably 40°C to 80°C, more preferably 40°C to 70°C, and even more preferably 40°C to 60°C.

[0085] To adjust the temperature of the molten ethylene carbonate, a heating device may be used, and the temperature of the heating device is preferably 50°C to 90°C, more preferably 50°C to 80°C, and even more preferably 50°C to 70°C. As for the heating device, a heater that can be directly attached or wound may be used, but considering the operability of the gas chromatograph's auto-injector and the handling workability of the syringe, a device that blows hot air is preferred.

[0086] The purity of the ethylene carbonate used in the analytical method according to the present embodiment is preferably 99.5 mass% or higher, more preferably 99.90 mass% or higher, and even more preferably 99.95 mass% or higher. According to the analytical method of the present embodiment, even with high-purity ethylene carbonate of 99.95 mass% or higher, high-precision analytical results can be obtained. In the past, it was difficult to determine the accurate purity of high-purity ethylene carbonate due to thermal decomposition, hydrolysis, etc., during analysis, but the analytical method of the present embodiment enables high-precision analysis. Furthermore, the purity of the ethylene carbonate is a value calculated based on the area ratio from the measurement results obtained, for example, by the analytical method according to the present embodiment.

[0087] The moisture content of the ethylene carbonate used in the analysis method according to the present embodiment is preferably 100 ppm or less, more preferably 60 ppm or less, and even more preferably 50 ppm or less. By using ethylene carbonate with a moisture content within this range, the hydrolysis of the ethylene carbonate can be suppressed after introduction into the gas chromatography apparatus, and analysis with higher precision becomes possible. The moisture content can be measured by the Karl Fischer method.

[0088] For a sample before being injected into a gas chromatography analysis device (1), a more stable analysis value can be obtained by performing an operation to suppress moisture absorption.

[0089] Sampling of the ethylene carbonate subject to analysis is performed by taking a small amount of ethylene carbonate from, for example, a purification tower in an ethylene carbonate manufacturing apparatus.

[0090] Sampling of ethylene carbonate is preferably performed at a temperature of 40°C or higher to achieve a molten state, but for short durations, the sampling environment may be any of dry inert gases such as dry nitrogen and dry argon, dry air, inert gas, air, or vacuum. Among these, dry inert gas, dry air, or vacuum is preferred, and dry nitrogen is more preferred. Here, "dry" in dry inert gas and dry air means that the dew point is -20°C or lower.

[0091] The sampled analytical sample is melted in a hot air circulation oven. The temperature inside the hot air circulation oven is preferably 50 to 80°C, more preferably 50 to 70°C, and even more preferably 55 to 65°C. Within this temperature range, ethylene carbonate can be efficiently melted after considering the effects of thermal decomposition. When checking the melting state, the container should be shaken with the cap closed to verify whether the analytical sample has melted. If the cap is not opened, the environment inside the hot air circulation oven may be any of air, inert gas, dry air, or dry inert gas. If the cap of the container is opened or closed while checking whether the analytical sample inside the hot air circulation oven has melted, the molten ethylene carbonate easily absorbs moisture and undergoes decomposition and hydrolysis. The cap must not be carelessly opened while the sampled analytical sample is in a molten state.

[0092] When using the auto-injector function of a gas chromatograph, it is necessary to collect a molten ethylene carbonate sample with a dropper and inject it into a vial. The environment in which this operation is performed may be any of air, inert gas, dry air, dry inert gas, or vacuum, provided that it is performed in a short time. Among these, dry inert gas, dry air, or vacuum are preferred, and dry nitrogen is more preferred.

[0093] When injecting ethylene carbonate by hand using a syringe in a gas chromatograph, the syringe is warmed in advance by placing it inside a hot air circulating oven or the like, and the cap of the container containing the sample is opened and collected under, for example, dry inert gas (preferably dry nitrogen), and the ethylene carbonate in the syringe is melted.

[0094] Before injecting ethylene carbonate into the gas chromatography analysis device (1), it is preferable to inject an organic solvent into the gas chromatography analysis device (1) to clean the column. For example, tetrahydrofuran may be used as the organic solvent. For cleaning, a portion of the vaporized organic solvent may be introduced into a capillary column through which an inert gas flows, under conditions similar to those for analyzing ethylene carbonate in the gas chromatography analysis device (1). This cleaning may be repeated, for example, three or more times.

[0095] The installation environment of the gas chromatograph may be an air-conditioned indoor environment (e.g., 15 to 35°C). Since ethylene carbonate becomes a solid at this temperature, in addition to melting it in advance as described above, the sample before being injected into the gas chromatograph must be thoroughly melted and confirmed to be actually melted.

[0096] The inlet temperature of the gas chromatography analysis device (1) is preferably 240 to 300°C, more preferably 250 to 290°C, and even more preferably 260 to 280°C.

[0097] The detector temperature of the gas chromatography analysis device (1) is preferably 240 to 300°C, more preferably 250 to 290°C, and even more preferably 260 to 280°C.

[0098] The inert gas (hereinafter also referred to as "carrier gas") circulated within the capillary column may be nitrogen or helium, but preferably nitrogen.

[0099] Gas chromatography analysis according to the present embodiment includes introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it through, but is controlled by the ratio of the inert gas flow rate discharged outside the capillary column and the inert gas flow rate introduced into the capillary column (hereinafter also referred to as the "split ratio"). The split ratio (inert gas flow rate discharged outside the capillary column: inert gas flow rate introduced into the capillary column) is preferably 5:1 to 50:1, more preferably 10:1 to 40:1, and even more preferably 15:1 to 30:1.

[0100] In a gas chromatography analysis method, it is preferable to set the carrier gas pressure when injecting the ethylene carbonate to be analyzed into the gas chromatography analysis device to 1.5 to 30 times the normal pressure, and then return the carrier gas pressure to the normal pressure after injection. Normal pressure refers to the normal flow rate of the carrier gas under measurement conditions and the pressure of the carrier gas under temperature conditions at the time of injection. By setting the pressure at the time of injection to 1.5 to 30 times, vaporization within the liner is promoted, thereby increasing the measurement precision.

[0101] Examples

[0102] The present invention will be explained more specifically below by way of examples, but the present invention is not limited to the following examples.

[0103] [Moisture content]

[0104] After drying in a 105°C dryer, approximately 3g of molten ethylene carbonate was collected in a syringe with a needle attached, which had been stored in a desiccator. The tip of the needle was covered with a silicone cap, and the weight was accurately measured. Then, the ethylene carbonate was injected into a Karl Fischer device under the following conditions, and the tip of the needle was covered with a silicone cap again, and the weight was measured. The amount of water was calculated by dividing the amount of Coulombs marked on the Karl Fischer device by the amount of ethylene carbonate obtained from the accurately measured weight.

[0105] <Measurement Conditions>

[0106] Karl Fischer Device: Mitsubishi Chemical Corp. CA-310

[0107] Anode Solution: Aquamicron AX

[0108] Cathode Solution: Aquamicron CXU

[0109] Injection sample volume: Approx. 3g

[0110] The gas chromatography analysis conditions performed in the following examples and comparative examples are shown.

[0111] Device: Agilent GC-7820A

[0112] Inlet temperature: 270℃

[0113] Injection volume: 0.4μL

[0114] Column: DB-1701 (30m length × hole diameter (inner) 0.53mm × 0.5㎛ thickness)

[0115] Column temperature: Maintain at 100℃ for 0 min, 10℃ / min (100 to 120℃),

[0116] 20℃ / min (120 to 220℃), hold at 220℃ for 6 min

[0117] Carrier gas: Nitrogen 1.0 ml / min

[0118] Typical pressure at injection temperature conditions: 1.0181 psi

[0119] Injection method: Split method (Split ratio 20:1)

[0120] Inlet liner: As described in the Examples and Comparative Examples

[0121] Detector: Hydrogen Flame Ionization Detector (FID) 270℃

[0122] Concentration calculation: Area percentage (based on all detected components of the gas chromatograph)

[0123] [Example 1]

[0124] Under dry air (dew point: -20°C or lower), two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state, were placed in a 60°C hot-air circulating oven with their caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph auto-injector while molten under dry nitrogen (purity 99.99%, dew point: -80°C or lower) and capped. The vial was set in the gas chromatograph auto-injector, and hot air was blown so that the periphery of the vial was approximately 60°C to prevent the ethylene carbonate inside the vial from solidifying. A single-taper liner (Agilent 5190-2292) that was not filled with wool was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0125] [Comparative Example 1]

[0126] Under dry nitrogen (99.99% purity, dew point: -80°C or lower), two capped polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state, were placed in a 60°C hot-air circulating oven. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph auto-injector while molten under dry nitrogen (99.99% purity, dew point: -40°C or lower) and capped. The vial was set in the gas chromatograph auto-injector, and hot air was blown so that the periphery of the vial was approximately 60°C to prevent the ethylene carbonate inside the vial from solidifying. A focus liner (Agilent 5190-2295) filled with wool was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0127] [Example 2]

[0128] Two polypropylene bottles containing high-purity ethylene carbonate for use as an electrolyte, sampled in a molten state under dry air (dew point: -20°C or lower), were placed in a 60°C hot-air circulating oven with their caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph's auto-injector while in a molten state under the air of the gas chromatograph installation environment, and the vial was capped. The vial was set in the gas chromatograph's auto-injector, and hot air was blown so that the periphery of the vial was about 60°C to prevent the ethylene carbonate in the vial from solidifying. A single-taper liner (Agilent 5190-2292) without wool was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0129] [Example 3]

[0130] Two polypropylene bottles containing high-purity ethylene carbonate for use as an electrolyte, sampled in a molten state under air, were placed in a circulating hot-air oven at 60°C with their caps closed. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph auto-injector in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or lower) and capped. The vial was set in the gas chromatograph auto-injector, and hot air was blown so that the periphery of the vial was about 60°C to prevent the ethylene carbonate in the vial from solidifying. A single-taper liner (Agilent 5190-2292) without wool was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0131] [Example 4]

[0132] Under dry nitrogen (99.99% purity, dew point: -40°C or lower), two capped polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state, were placed in a 60°C hot-air circulating oven. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph auto-injector while molten under dry nitrogen (99.99% purity, dew point: -80°C or lower) and capped. The vial was set in the gas chromatograph auto-injector, and hot air was blown so that the periphery of the vial was approximately 60°C to prevent the ethylene carbonate inside the vial from solidifying. A single-taper liner (Agilent 5190-2292) that was not filled with wool was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0133] [Example 5]

[0134] Under dry nitrogen (99.99% purity, dew point: -80°C or lower), two capped polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state, were placed in a 60°C hot-air circulating oven. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using the sample from one polypropylene bottle. Using the sample from the other polypropylene bottle, the required amount for analysis was placed into a vial for the gas chromatograph auto-injector while molten under dry nitrogen (99.99% purity, dew point: -80°C or lower) and capped. The vial was set in the gas chromatograph auto-injector, and hot air was blown so that the periphery of the vial was approximately 60°C to prevent the ethylene carbonate inside the vial from solidifying. A single-taper liner (Agilent 5190-2292) that was not filled with wool was set in the gas chromatograph, and gas chromatographic analysis was performed using the pressurized injection function of the gas chromatograph (pressurized injection condition: pressure 2 psi before the start of analysis).

[0135]

[0136] The meanings of the abbreviations in Table 1 are as follows.

[0137] EO: Ethylene oxide, EG: Ethylene glycol, DEG: Diethylene glycol, EC: Ethylene carbonate, TEG: Triethylene glycol Industrial applicability

[0138] With the expansion of LiB usage, the demand for high-purity ethylene carbonate for electrolyte applications is expected to increase in the future. Accurately evaluating the purity and impurities of high-purity ethylene carbonate leads to the provision of high-quality electrolyte solvents and can contribute to the improvement of battery performance.

[0139] This application claims priority based on Japanese Patent Application No. 2021-096700. All contents of the said Japanese Patent Application are incorporated herein by reference. Explanation of the symbols

[0140] 1: Gas chromatography analysis device 11: Injection part 12: Liner 14: Injection housing 20: Capillary Column 30: Detector 141: O-ring 142: Inert gas introduction section 143: Inert gas outlet

Claims

Claim 1 A gas chromatographic analysis method by split injection of ethylene carbonate, comprising: injecting the ethylene carbonate to be analyzed into a gas chromatographic analysis device; vaporizing the injected ethylene carbonate within a single-taper liner that is not filled with wool; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it; and detecting the ethylene carbonate that has passed through the capillary column by a detector. Claim 2 A gas chromatographic analysis method by split injection of ethylene carbonate, comprising: injecting molten ethylene carbonate of the subject of analysis into a gas chromatographic analysis device; vaporizing the injected ethylene carbonate within a liner; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing it; and detecting the ethylene carbonate that has passed through the capillary column by a detector. Claim 3 A gas chromatography analysis method according to paragraph 2, wherein the liner is a single-taper liner that is not filled with wool. Claim 4 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the moisture content of the ethylene carbonate to be analyzed is 100 ppm or less. Claim 5 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the purity of the ethylene carbonate to be analyzed is 99.5 mass% or higher. Claim 6 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the carrier gas pressure when injecting the ethylene carbonate to be analyzed into the gas chromatography analysis device is 1.5 to 30 times the normal pressure, and after injection, the carrier gas pressure is set to the normal pressure. Claim 7 A gas chromatography analysis method according to any one of claims 1 to 3, further comprising collecting the ethylene carbonate to be analyzed into a syringe for injection of a gas chromatograph under dry inert gas. Claim 8 A gas chromatography analysis method according to any one of claims 1 to 3, further comprising placing the ethylene carbonate to be analyzed into a vial for an auto-injector of a gas chromatograph under a dry inert gas and closing the stopper. Claim 9 A gas chromatography analysis method according to any one of claims 1 to 3, further comprising sampling the ethylene carbonate of the subject of analysis under dry air, under dry inert gas, or under vacuum. Claim 10 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the liquid phase in the capillary column comprises at least one component selected from the group consisting of polysiloxane substituted with cyanopropyl and phenyl, polysiloxane substituted with cyanopropyl and methyl, polysiloxane substituted with trifluoropropyl, polysiloxane substituted with phenyl, and polyethylene glycol. Claim 11 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the inlet temperature of the gas chromatography analysis device is 250 to 290℃. Claim 12 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the detector temperature of the gas chromatography analysis device is 240 to 300℃. Claim 13 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the inert gas circulated within the capillary column is nitrogen or helium. Claim 14 A gas chromatography analysis method according to any one of claims 1 to 3, wherein the split ratio (flow rate of inert gas discharged outside the capillary column: flow rate of inert gas introduced into the capillary column) is 5:1 to 50:1.

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