Gas Chromatography Analysis

Abstract

The present invention addresses the problem of providing a gas chromatography analysis method which can accurately analyze the purity of ethylene carbonate with high purity by means of gas chromatography analysis, wherein the problem can be addressed by the gas chromatography analysis method, which is a gas chromatography analysis method for ethylene carbonate, via a split injection method, the method comprising: injecting ethylene carbonate to be analyzed into a gas chromatography analysis device; vaporizing the injected ethylene carbonate within a single tapered liner not filled with wool; introducing and passing a portion of the vaporized ethylene carbonate to and through a capillary column through which an inert gas has flowed; and detecting the ethylene carbonate passed through the capillary column by means of a detector.

Description

[Technical field]

[0001] The present invention relates to gas chromatography analytical methods. [Background technology]

[0002] In recent years, lithium-ion secondary batteries (LiBs) have been attracting increasing attention as they contribute to reducing the burden on the global environment through energy conservation and resource saving. Recently, the range of uses for LiBs has been expanding not only to batteries for mobile devices such as smartphones and tablets, but also to in-vehicle batteries for hybrid cars (HEVs) and electric vehicles (EVs), and even to batteries for power storage. LiBs are secondary batteries that charge and discharge by the movement of lithium ions between the positive and negative electrodes, and are composed of four main materials: a positive electrode, a negative electrode, a separator, and an electrolyte. Highly polar ethylene carbonate is a representative electrolyte solvent because it dissolves and dissociates lithium salts at high concentrations, forms a nanometer-order coating on the surface of the negative electrode of the carbon material, and has the advantage of stabilizing the carbon material of the negative electrode. However, there is a concern that impurities in ethylene carbonate may affect battery performance during the charge and discharge cycle of the battery, so high-purity ethylene carbonate is used for electrolyte applications.

[0003] In the field of lithium ion battery production, various methods have been proposed for measuring the heteroalcohol content in ethylene carbonate in lithium ion battery electrolytes (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] CN105319303A Summary of the Invention [Problem to be solved by the invention]

[0005] In the analysis 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 accuracy of the measurement results due to the decomposition of ethylene carbonate in a gas chromatography analyzer. Therefore, a method of analyzing ethylene carbonate with higher accuracy is required.

[0006] That is, an object of the present invention is to provide a gas chromatography analysis method which enables the purity of high-purity ethylene carbonate to be analyzed with high accuracy by gas chromatography analysis. [Means for solving the problem]

[0007] As a result of intensive investigations aimed at solving the above-mentioned problems, the present inventors have found that the purity of high purity ethylene carbonate can be analyzed with high accuracy by introducing a sample into a capillary column using a single taper liner that is not packed with wool in a split gas chromatography analysis method, and have completed the present invention.

[0008] Furthermore, as a result of intensive investigations aimed at solving the above-mentioned problems, the present inventors have found that in a gas chromatography analysis method using the split method, the purity of high purity ethylene carbonate can be analyzed with high accuracy by injecting ethylene carbonate in a molten state into a gas chromatography analyzer, and have completed the present invention.

[0009] That is, the present invention is as follows. [1] A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting ethylene carbonate to be analyzed into a gas chromatography analyzer; vaporizing the injected ethylene carbonate in a single taper liner not filled with wool; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; A gas chromatography analysis method comprising: [2] A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting molten ethylene carbonate to be analyzed into a gas chromatography analyzer; 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 is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; A gas chromatography analysis method comprising: [3] The gas chromatography analysis method according to [2], wherein the liner is a single taper liner that is not filled with wool. [4] The gas chromatography analysis method according to any one of [1] to [3], wherein the water content of the ethylene carbonate to be analyzed is 100 ppm or less. [5] The gas chromatography analysis method according to any one of [1] to [4], wherein the purity of the ethylene carbonate to be analyzed is 99.5 mass % or more. [6] The gas chromatography analysis method according to any one of [1] to [5], wherein a carrier gas pressure when injecting the ethylene carbonate to be analyzed into the gas chromatography analyzer is set to 1.5 to 30 times the normal pressure, and after the injection, the carrier gas pressure is returned to the normal pressure. [7] The gas chromatography analysis method according to any one of [1] to [6], further comprising collecting the ethylene carbonate to be analyzed in an injection syringe for a gas chromatograph under a dry inert gas. [8] The gas chromatography analysis method according to any one of [1] to [6], further comprising placing the ethylene carbonate to be analyzed in a vial for an autoinjector of a gas chromatograph under a dry inert gas, and sealing the vial. [9] The gas chromatography analysis method according to any one of [1] to [8], further comprising sampling the ethylene carbonate to be analyzed under dry air, under a dry inert gas, or under vacuum.

[10] The gas chromatography analysis method according to any one of [1] to [9], wherein the liquid phase in the capillary column contains at least one component selected from the group consisting of polysiloxanes substituted with cyanopropyl and phenyl, polysiloxanes substituted with cyanopropyl and methyl, polysiloxanes substituted with trifluoropropyl, polysiloxanes substituted with phenyl, and polyethylene glycol.

[11] The gas chromatography analysis method according to any one of [1] to

[10] , wherein the injection port temperature of the gas chromatography analyzer is 250 to 290°C.

[12] The gas chromatography analysis method according to any one of [1] to

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

[13] The gas chromatography analysis method according to any one of [1] to

[12] , wherein the inert gas caused to flow through the capillary column is nitrogen or helium.

[14] The gas chromatography analysis method according to any one of [1] to

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

[0010] According to the present invention, there is provided a gas chromatography analysis method which is capable of accurately analyzing the purity of high-purity ethylene carbonate by gas chromatography analysis. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows a schematic configuration diagram of a gas chromatography analysis device 1. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a single taper liner. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention (hereinafter, also referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and can be practiced in various modifications within the scope of the gist of the present invention.

[0013] The gas chromatography analysis method according to this embodiment is as follows: A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting ethylene carbonate to be analyzed into a gas chromatography analyzer; vaporizing the injected ethylene carbonate in a single taper liner not filled with wool; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; Includes.

[0014] According to the present embodiment including the above-described configuration, the purity of high-purity ethylene carbonate can be analyzed with high accuracy by gas chromatography analysis.

[0015] In gas chromatography analysis, when separating with a capillary column, it is common to apply a split method in which, after vaporizing an injected sample, not the entire amount is introduced into the capillary column, but only an appropriate amount of sample according to the retention capacity of the capillary column is introduced into the capillary column, and the remainder is exhausted from a vent together with an inert gas. In the split method, a liner filled with wool is commonly used. This is because it has the advantage of efficiently vaporizing the sample and being able to analyze with good reproducibility. Therefore, the present inventor also initially used a liner filled with wool for split method analysis in gas chromatography analysis of high-purity ethylene carbonate for electrolyte use, but could not obtain measurement accuracy for purity and impurity concentration. Furthermore, other liners for split method analysis and liners filled with wool for splitless method analysis were tried, but reproducibility for purity and impurity concentration was not obtained. The inventors of the present invention have considered that splitless liners not filled with wool are not used in split method analysis because reproducibility is likely to be poor, but that the surface of the wool, which is intended to facilitate efficient vaporization, may be prone to thermal decomposition or hydrolysis of ethylene carbonate. Thus, they have investigated liners not filled with wool and found a single taper liner for splitless analysis as a liner shape that provides good reproducibility of analytical values. Selecting a liner for the splitless method in a split method analysis is surprising, since it would be common sense to deteriorate 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 gas chromatography analysis of high purity ethylene carbonate.

[0016] The gas chromatography analysis method according to this embodiment is as follows: A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting molten ethylene carbonate to be analyzed into a gas chromatography analyzer; 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 is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; Includes.

[0017] According to the present embodiment including the above-described configuration, the purity of high-purity ethylene carbonate can be analyzed with high accuracy by gas chromatography analysis.

[0018] The gas chromatography analysis according to this embodiment includes introducing and passing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas is flowing. In other words, the gas chromatography analysis according to this embodiment is an analysis by a split injection method. In the split injection method, the analysis sample is vaporized in the liner while maintaining the component concentration ratio of the sample, and a portion of the vapor is introduced into the capillary column, resulting in a reproducible analysis. Components with different boiling points can also be vaporized simultaneously in the sample liquid in the liner, and the sample is introduced into the capillary column while maintaining the component concentration ratio of the sample.

[0019] However, this is not the case with ethylene carbonate, which is solid at room temperature. After ethylene carbonate is injected into a gas chromatograph, phase transitions such as melting and vaporization occur, but the inventor suspected that vaporization is inhibited by the endothermic phenomenon caused by the enthalpy of fusion, making it more likely that thermal decomposition or hydrolysis occurs than vaporization. Therefore, the inventor introduced molten ethylene carbonate into a gas chromatography analyzer, which made it possible to simultaneously vaporize components with different boiling points in the liner, preventing thermal decomposition and hydrolysis and improving the accuracy of the gas chromatography analysis method.

[0020] In the above-mentioned embodiment, it is preferable to simultaneously inject molten ethylene carbonate into a gas chromatography analyzer and vaporize the ethylene carbonate in a single-tapered injection liner that is not filled with wool. By simultaneously performing these steps, the introduction of molten ethylene carbonate facilitates vaporization in the liner, and vaporization in the liner is smooth without adhesion to the wool in the liner. Therefore, according to this analysis method, a synergistic effect due to the above-mentioned characteristics is exerted, and even more excellent accuracy of the gas chromatography analysis method can be obtained.

[0021] The gas chromatography analyzer 1 used in this embodiment will be described below. 1 shows a schematic configuration diagram of a gas chromatography analyzer 1. The gas chromatography analyzer 1 includes an injection section 11, a liner 12, an injection housing 14, a capillary column 20, and a detector 30.

[0022] Although not shown, the injection section 11 is provided with a septum, and is configured so that a sample can be injected using a microsyringe through the septum.

[0023] The liner 12 is preferably a single taper injection liner that is not filled with wool. By using this liner, the purity of high purity ethylene carbonate can be analyzed with high accuracy. Specifically, it is preferable to use a single taper liner as shown in FIG. 2 as the liner 12. The material of the liner may be either quartz or glass, as long as it has been inactivated. Materials other than quartz and glass can also be used as long as they are inactivated so that the high purity ethylene carbonate for electrolyte use and the impurities contained therein do not become activated and react within the liner.

[0024] Wool is wool used in gas chromatography analysis, such as glass wool.

[0025] The term "single taper" refers to a configuration in which one taper structure is provided.

[0026] The liner 12 is fixed inside the injection housing 14 via an O-ring 141. The injection housing 14 is provided with an inert gas inlet 142. The inert gas introduced from the inert gas inlet 142 passes through the inside of the liner 12, with a portion of the inert gas being introduced into the capillary column and the rest being exhausted from an inert gas outlet 143 provided in the injection housing 14.

[0027] The capillary column 20 is preferably a capillary column having a polar liquid phase. From the viewpoint of enhancing the separation ability of impurities contained in ethylene carbonate, the liquid phase in the capillary column 20 preferably contains 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. Among these, a combination of polysiloxane substituted with cyanopropyl and phenyl, and dimethylsiloxane is preferred.

[0028] As long as the separation and quantification of peaks in an actual chromatogram can be confirmed, the column length, column pore size, and liquid phase thickness can be selected from the lineup of columns available on the market.

[0029] The detector 30 is not particularly limited as long as it is a detector used in gas chromatography analysis, and examples thereof include a flame ionization detector (FID), a mass spectrometer (MS), and a micro thermal conductivity detector (μTCD).

[0030] Next, the gas chromatography analysis method according to this embodiment will be described using an example in which the gas chromatography analysis device 1 is used.

[0031] Ethylene carbonate is injected into the gas chromatography analyzer 1. The ethylene carbonate is injected from the injection part 11. The injected ethylene carbonate is then introduced into the liner 12 and vaporized in the liner 12. A part of the vaporized ethylene carbonate is introduced into and passed through the capillary column 20 through which an inert gas is flowing. After passing through the capillary column 20, the ethylene carbonate is detected by the detector 30.

[0032] The ethylene carbonate is preferably in a molten state when injected into the gas chromatography analyzer 1. By injecting molten ethylene carbonate, components having different boiling points in the liner can be vaporized at the same time, thermal decomposition and hydrolysis can be prevented, and the accuracy of the gas chromatography analysis can be improved.

[0033] 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.

[0034] A heating device may be used to adjust the temperature of the molten ethylene carbonate, and the temperature of the heating device is preferably 50° C. to 90° C., more preferably 50° C. to 80° C., and further preferably 50° C. to 70° C. The heating device may be a heater that can be directly attached or wrapped around the material, but in consideration of the operability of the autoinjector of the gas chromatograph and the handling and workability of the syringe, a device that applies hot air is preferred.

[0035] The purity of ethylene carbonate used in the analysis method according to this embodiment is preferably 99.5% by mass or more, more preferably 99.90% by mass or more, and even more preferably 99.95% by mass or more. According to the analysis method according to this embodiment, it is possible to obtain accurate analysis results even for ethylene carbonate with a high purity of 99.95% by mass or more. Conventionally, it has been difficult to obtain an accurate purity of high-purity ethylene carbonate due to thermal decomposition, hydrolysis, etc. during analysis, but the analysis method according to this embodiment makes it possible to perform a highly accurate analysis. The purity of the ethylene carbonate is, for example, a value calculated based on an area ratio from the measurement results obtained by the analysis method according to this embodiment.

[0036] The water content of the ethylene carbonate used in the analysis method according to this embodiment is preferably 100 ppm or less, more preferably 60 ppm or less, and further preferably 50 ppm or less. By using ethylene carbonate having a water content within this range, hydrolysis of the ethylene carbonate can be suppressed after introduction into a gas chromatography device, enabling more accurate analysis. The water content can be measured by the Karl Fischer method.

[0037] Before being injected into the gas chromatography analyzer 1, the sample may be subjected to an operation to suppress moisture absorption, thereby making it possible to obtain a more stable analytical value.

[0038] Sampling of the ethylene carbonate to be analyzed is carried out, for example, by taking a small amount of ethylene carbonate from a purification column in an ethylene carbonate production apparatus.

[0039] Sampling of ethylene carbonate is preferably performed at 40°C or higher in order to place the ethylene carbonate in a molten state. Since the sampling time is short, the sampling environment may be any of dry inert gases such as dry nitrogen and dry argon, dry air, inert gas, air, and vacuum. Among these, dry inert gas, dry air, and vacuum are 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.

[0040] The sampled analytical sample is melted in a hot air circulation oven. The temperature in 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. In this temperature range, ethylene carbonate can be efficiently melted while taking into consideration the influence of thermal decomposition. When checking the melted state, the container should be shaken with the cap of the container closed to check whether the analytical sample has melted. If the cap is not opened, the environment in the hot air circulation oven may be any of air, inert gas, dry air, and dry inert gas. When checking whether the analytical sample in the hot air circulation oven has melted, if the cap of the container is opened and closed, ethylene carbonate in the molten state easily absorbs moisture, decomposes, and hydrolyzes. The cap of the sampled analytical sample in the molten state should not be opened carelessly.

[0041] When using the auto-injector function of the gas chromatograph, it is necessary to collect the 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, and vacuum, so long as it is performed in a short time. Among these, dry inert gas, dry air, and vacuum are preferred, and dry nitrogen is more preferred.

[0042] When ethylene carbonate is manually injected into the gas chromatograph using a syringe, the syringe is warmed in advance in the above-mentioned warm air circulating oven or the like, and the cap of a container containing a sample is opened under, for example, a dry inert gas (preferably dry nitrogen) to collect the sample, and the ethylene carbonate in the syringe is melted.

[0043] Before injecting ethylene carbonate into the gas chromatography analyzer 1, it is preferable to inject an organic solvent into the gas chromatography analyzer 1 to wash the inside of the column. An example of the organic solvent used here is tetrahydrofuran. The washing may be performed under the same conditions as those for analyzing ethylene carbonate with the gas chromatography analyzer 1, by introducing a part of the vaporized organic solvent into a capillary column through which an inert gas is flowing and passing the organic solvent. The washing may be repeated, for example, three or more times.

[0044] The environment in which the gas chromatograph is installed may be an air-conditioned indoor environment (for example, 15 to 35° C.). At this environmental temperature, ethylene carbonate becomes solid, so in addition to melting it in advance as described above, it is necessary to reliably melt the sample before injecting it into the gas chromatograph and confirm that it is actually melted.

[0045] The injection port temperature of the gas chromatography analyzer 1 is preferably 240 to 300°C, more preferably 250 to 290°C, and further preferably 260 to 280°C.

[0046] The detector temperature of the gas chromatography analyzer 1 is preferably 240 to 300°C, more preferably 250 to 290°C, and further preferably 260 to 280°C.

[0047] The inert gas (hereinafter also referred to as "carrier gas") that is caused to flow through the capillary column may be nitrogen or helium, but is preferably nitrogen.

[0048] The gas chromatography analysis according to this embodiment involves introducing a part of the vaporized ethylene carbonate into a capillary column through which an inert gas flows and passing the part, and adjusting the ratio of the flow rate of the inert gas discharged out of the capillary column to the flow rate of the inert gas introduced into the capillary column (hereinafter also referred to as "split ratio"). The split ratio (flow rate of the inert gas discharged out of the capillary column:flow rate of the inert gas introduced into the capillary column) is preferably 5:1 to 50:1, more preferably 10:1 to 40:1, and further preferably 15:1 to 30:1.

[0049] In the gas chromatography analysis method, it is preferable that the carrier gas pressure when injecting the ethylene carbonate to be analyzed into a gas chromatography analyzer is 1.5 to 30 times the normal pressure, and after injection, the carrier gas pressure is returned to the normal pressure. The normal pressure is the pressure of the carrier gas when the flow rate of the carrier gas is constant under the measurement conditions and the temperature conditions are the same at the time of injection. In contrast, by setting the pressure at the time of injection to 1.5 to 30 times, vaporization in the liner is promoted, and the measurement accuracy can be further improved. EXAMPLES

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0051] [Moisture content] After drying in a dryer at 105°C, about 3 g of molten ethylene carbonate was placed in a syringe with a needle that had been stored in a desiccator, the tip of the needle was capped with a silicone cap, and the weight was accurately measured. The ethylene carbonate was then injected into a Karl Fischer apparatus under the following conditions, and the tip of the needle was again capped with a silicone cap and the weight was measured. The amount of coulombs displayed on the Karl Fischer was divided by the amount of ethylene carbonate calculated from the accurately measured weight to determine the amount of water.

[0052] <Measurement conditions> Karl Fischer apparatus: Mitsubishi Chemical Corporation CA-310 Anolyte: Aquamicron AX Catholyte: Aquamicron CXU Injection sample amount: approx. 3g

[0053] The gas chromatography analysis conditions used in the following Examples and Comparative Examples are as follows. Equipment: Agilent GC-7820A Inlet temperature: 270℃ Injection volume: 0.4μL Column: DB-1701 (30m length x pore diameter (inner diameter) 0.53mm x 0.5μm thickness) Column temperature: 100°C for 0 min, 10°C / min (100-120°C), 20℃ / min (120~220℃), hold at 220℃ for 6 minutes Carrier gas: Nitrogen 1.0ml / min Normal pressure at injection temperature: 1.0181 psi Injection method: Split method (split ratio 20:1) Inlet liner: as described in the Examples and Comparative Examples Detector: Flame ionization detector (FID) 270℃ Concentration calculation: Area percentage (based on all components detected by gas chromatograph)

[0054] [Example 1] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state under dry air (dew point: -20°C or less), were placed in a hot air circulating oven at 60°C with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one of the polypropylene bottles. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the autoinjector of the gas chromatograph in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or less) and capped. The vial was set in the autoinjector of the gas chromatograph, and hot air was blown so that the temperature around 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 filling was set in the gas chromatograph, and gas chromatography analysis was performed.

[0055] [Comparative Example 1] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or less), were placed in a hot air circulating oven at 60°C with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one polypropylene bottle. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the autoinjector of the gas chromatograph under dry nitrogen (purity 99.99%, dew point: -40°C or less) in a molten state, and the vial was capped. The vial was set in the autoinjector of the gas chromatograph, and hot air was blown around the vial to keep the temperature at about 60°C so that the ethylene carbonate in the vial would not solidify. A focus liner (Agilent 5190-2295) filled with wool was set in the gas chromatograph, and gas chromatography analysis was performed.

[0056] [Example 2] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state under dry air (dew point: -20°C or less), were placed in a hot air circulating oven at 60°C with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one of the polypropylene bottles. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the gas chromatograph autoinjector 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 autoinjector, and hot air was blown around the vial to keep the temperature at about 60°C so that the ethylene carbonate in the vial would not solidify. A single taper liner (Agilent 5190-2292) without wool filling was set in the gas chromatograph, and gas chromatographic analysis was performed.

[0057] [Example 3] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use sampled in a molten state under air were placed in a hot air circulating oven at 60°C with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one of the polypropylene bottles. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the autoinjector of a gas chromatograph in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or less) and capped. The vial was set in the autoinjector of the gas chromatograph, and hot air was blown so that the temperature around 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 filling was set in the gas chromatograph, and gas chromatography analysis was performed.

[0058] [Example 4] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state under dry nitrogen (purity 99.99%, dew point: -40°C or less), were placed in a hot air circulating oven at 60°C with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one of the polypropylene bottles. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a vial for the autoinjector of the gas chromatograph under dry nitrogen (purity 99.99%, dew point: -80°C or less) in a molten state, and the vial was capped. The vial was set in the autoinjector of the gas chromatograph, and hot air was blown so that the temperature around 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 filling was set in the gas chromatograph, and gas chromatography analysis was performed.

[0059] [Example 5] Two polypropylene bottles containing high-purity ethylene carbonate for electrolyte use, sampled in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or less), were placed in a 60°C warm air circulating oven with the caps on. It was confirmed that the entire ethylene carbonate had melted. The moisture content was measured using a sample from one of the polypropylene bottles. Using a sample from the other polypropylene bottle, the required amount for analysis was placed in a gas chromatograph autoinjector vial in a molten state under dry nitrogen (purity 99.99%, dew point: -80°C or less) and capped. The vial was set in the gas chromatograph autoinjector, and warm air was blown around the vial to keep the temperature at about 60°C to prevent the ethylene carbonate in the vial from solidifying. A single taper liner (Agilent 5190-2292) 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 conditions: pressure before analysis started: 2 psi).

[0060] [Table 1]

[0061] The abbreviations in Table 1 have the following meanings: EO: Ethylene oxide, EG: Ethylene glycol, DEG: Diethylene glycol, EC: Ethylene carbonate, TEG: Triethylene glycol [Industrial Applicability]

[0062] Demand for high-purity ethylene carbonate for electrolyte use is expected to grow in line with the expansion of LiB use. Correct evaluation of the purity and impurities of high-purity ethylene carbonate will lead to the provision of a high-quality electrolyte solvent, which will contribute to improving battery performance.

[0063] This application claims priority based on Japanese Patent Application No. 2021-096700, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0064] 1. Gas chromatography analyzer 11...Injection part 12. Liner 14…Injection housing 20...Capillary column 30…Detector 141…O-ring 142...Inert gas inlet 143...Inert gas outlet section

Claims

1. A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting ethylene carbonate to be analyzed into a gas chromatography analyzer; vaporizing the injected ethylene carbonate in a single taper liner not filled with wool; introducing a portion of the vaporized ethylene carbonate into a capillary column through which an inert gas is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; A gas chromatography analysis method comprising:

2. A method for the split injection gas chromatography analysis of ethylene carbonate, comprising the steps of: Injecting molten ethylene carbonate to be analyzed into a gas chromatography analyzer; 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 is flowed and passing the portion; detecting the ethylene carbonate that has passed through the capillary column with a detector; A gas chromatography analysis method comprising:

3. 3. The gas chromatography method of claim 2, wherein the liner is a single taper liner that is not filled with wool.

4. The gas chromatography analysis method according to any one of claims 1 to 3, wherein the water content of the ethylene carbonate to be analyzed is 100 ppm or less.

5. The gas chromatography analysis method according to any one of claims 1 to 4, wherein the purity of the ethylene carbonate to be analyzed is 99.5 mass% or more.

6. 6. The gas chromatography analysis method according to claim 1, wherein a carrier gas pressure when injecting the ethylene carbonate to be analyzed into the gas chromatography analyzer is set to 1.5 to 30 times the normal pressure, and after the injection, the carrier gas pressure is returned to the normal pressure.

7. 7. The gas chromatography analysis method according to claim 1, further comprising collecting the ethylene carbonate to be analyzed under a dry inert gas into a syringe for injection into a gas chromatograph.

8. The gas chromatography analysis method according to any one of claims 1 to 6, further comprising placing the ethylene carbonate to be analyzed in a vial for an autoinjector of a gas chromatograph under a dry inert gas and sealing the vial.

9. 9. The gas chromatography method of claim 1, further comprising sampling the ethylene carbonate to be analyzed under dry air, under a dry inert gas, or under vacuum.

10. 10. The gas chromatography analysis method according to claim 1, wherein the liquid phase in the capillary column contains at least one component selected from the group consisting of cyanopropyl- and phenyl-substituted polysiloxanes, cyanopropyl- and methyl-substituted polysiloxanes, trifluoropropyl-substituted polysiloxanes, phenyl-substituted polysiloxanes, and polyethylene glycol.

11. The gas chromatography analysis method according to any one of claims 1 to 10, wherein the inlet temperature of the gas chromatography analyzer is 250 to 290°C.

12. The gas chromatography analysis method according to any one of claims 1 to 11, wherein the detector temperature of the gas chromatography analyzer is 240 to 300°C.

13. The gas chromatography analysis method according to any one of claims 1 to 12, wherein the inert gas flowing through the capillary column is nitrogen or helium.

14. The gas chromatography analysis method according to any one of claims 1 to 13, wherein a split ratio (flow rate of the inert gas discharged outside the capillary column:flow rate of the inert gas introduced into the capillary column) is 5:1 to 50:1.

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