Method for determining elements in non-aqueous solutions

Abstract

To provide a method for quantizing an element in a non-aqueous solution with which an element in a non-aqueous solution can be accurately quantized.SOLUTION: A method for quantizing an element in a non-aqueous solution includes: dispensing part of a non-aqueous solution; diluting the dispensed non-aqueous solution by using Ar gas; and analyzing an element to be analyzed contained in the diluted non-aqueous solution by using ICP emission spectrochemical analysis or ICP mass spectrometry.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for quantifying an element in a non-aqueous solution. [Background technology]

[0002] The amount of precipitates and / or inclusions (hereinafter sometimes referred to as "precipitates, etc.") present in a metallic material significantly affects various properties of the metallic material (e.g., fatigue characteristics, hot workability, cold workability, deep drawability, machinability, etc.). For this reason, it is important to determine the amount of precipitates, etc.

[0003] Known methods for extracting and quantifying deposits and the like in metal materials include, for example, the acid decomposition method, the halogen method, and the electrolytic extraction method. Of these, electrolytic extraction is a method that utilizes the potential difference between the matrix of a metal material and the precipitates, etc. to dissolve only the matrix and coagulate the precipitates, etc. present in the electrolyte, filter them, recover them, and analyze them. In electrowinning, by changing the electrolysis conditions (voltage, current value), it is possible to electrolyze a specific structure of a metal material and finely adjust the amount of dissolution (hereinafter sometimes referred to as the "amount of electrolysis"). For this reason, electrowinning is the method that is commonly used. In particular, when all of the deposits and the like are to be extracted from the metal material without loss, electrolytic extraction using a non-aqueous solvent-based electrolyte is used.

[0004] The precipitates collected by the electrolytic extraction method are dissolved using an acid or the like, and then quantitatively analyzed. Incidentally, the precipitates in metal materials are often poorly soluble substances such as carbides, sulfides, nitrides, and oxides. However, there is no direct method for confirming whether or not the precipitate has been completely dissolved in the acid.

[0005] Therefore, a method of indirectly determining the amount of precipitates and the like using the following formula (1) can be considered. Total.A = pre.A + sol.A (1) In the above formula (1), pre.A: Mass concentration of element A constituting the deposit of the metal material sol.A: mass concentration of element A dissolved in the matrix of a metal material (solubility content) Total.A: Total mass concentration of element A contained in the metal material It is.

[0006] By determining the values ​​of Total.A and sol.A from the above formula (1), pre.A (that is, the mass concentration of element A constituting the precipitate, etc.) can be determined. Total.A can be calculated by spark discharge optical emission spectrometry (JIS G 1253), etc. Sol.A can be calculated by dividing the mass of element A in the electrolyte after electrolytic extraction by the difference in mass of the metal material before and after electrolysis (amount of electrolysis).

[0007] Patent Document 1 discloses a method for determining sol.A. In the method disclosed in Patent Document 1, a metal material is first electrolyzed in an electrolytic solution (non-aqueous solvent-based electrolytic solution), a portion of the electrolytic solution is sampled, and the non-aqueous solvent is removed by drying to obtain an aqueous solution. Then, the concentration ratio of the target element A to the comparative element B in the aqueous solution is calculated. The calculated concentration ratio is multiplied by the separately determined content of the comparative element B in the metal material to correct the concentration ratio, thereby obtaining sol. A. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2009-31269 A Summary of the Invention [Problem to be solved by the invention]

[0009] The method disclosed in Patent Document 1 is a method for removing the non-aqueous solvent by drying, which may be undesirable from the viewpoint of environmental regulations. In addition, when the comparative element B forms a precipitate or the like in the metal material, the accurate concentration of the target element A cannot be calculated. Furthermore, the analytical accuracy decreases when the concentration of the target element A is low relative to the concentration of the reference element B. In addition, this method cannot be applied to non-aqueous solutions in which the reference element B is not present.

[0010] In light of the above, the present inventors have investigated a method of separating a non-aqueous solution and analyzing the target element contained in the separated non-aqueous solution.

[0011] When quantifying elements in an aqueous solution, for example, ICP atomic emission spectrometry or ICP mass spectrometry (hereinafter, both may be collectively referred to as "ICP analysis") is used. In ICP (Inductively Coupled Plasma) analysis, an aqueous solution containing the element to be analyzed is sprayed and introduced into Ar (argon) plasma, and the elements contained in the aqueous solution are ionized and analyzed.

[0012] Therefore, the present inventors have investigated the use of ICP analysis for the analysis of trace elements contained in non-aqueous solutions. However, when a non-aqueous solution is introduced into the Ar plasma, the higher the concentration of the non-aqueous solvent in the non-aqueous solution, the more unstable the excitation and / or emission behavior in the Ar plasma becomes, and the lower the analytical accuracy becomes. Furthermore, there were cases where the Ar plasma disappeared, making analysis impossible. In addition, when the non-aqueous solution was diluted to reduce the concentration of the non-aqueous solvent to a level at which the Ar plasma was stable, the concentration of the elements to be analyzed also decreased, again resulting in a decrease in analytical accuracy and making it impossible to quantify trace elements.

[0013] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a method for quantifying elements in a non-aqueous solution, which can accurately quantify the elements in the non-aqueous solution. [Means for solving the problem]

[0014] As a result of extensive investigations, the present inventors have found that the above object can be achieved by employing the following configuration, and have completed the present invention.

[0015] That is, the present invention provides the following [1] to [7]. [1] A method for quantifying elements in a non-aqueous solution, comprising: taking a portion of the non-aqueous solution; diluting the taken non-aqueous solution with Ar gas; and analyzing the elements to be analyzed contained in the diluted non-aqueous solution using ICP atomic emission spectrometry or ICP mass spectrometry. [2] The method for quantifying elements in a non-aqueous solution according to [1] above, wherein the non-aqueous solution is sprayed and introduced into Ar plasma using a carrier gas, and the Ar gas is caused to flow in a direction perpendicular to the flow direction of the carrier gas, thereby diluting the non-aqueous solution introduced into the Ar plasma. [3] A method for quantifying elements in a non-aqueous solution according to [1] or [2] above, wherein interfering elements contained in the non-aqueous solution are removed when analyzing the elements to be analyzed contained in the non-aqueous solution. [4] The method for quantifying elements in a non-aqueous solution according to any one of the above [1] to [3], wherein the non-aqueous solution is an electrolytic solution obtained after electrolyzing a metal material. [5] The method for quantifying elements in a non-aqueous solution according to any one of [1] to [4] above, wherein the material of an apparatus that comes into contact with the non-aqueous solution is at least one selected from the group consisting of borosilicate glass, quartz glass, and fluorine-based resins. [6] The method for quantifying an element in a non-aqueous solution according to any one of [1] to [5] above, wherein the element to be analyzed contained in the non-aqueous solution is Al. [7] The method for quantifying an element in a non-aqueous solution according to any one of [1] to [6] above, wherein the flow rate of the carrier gas is 0.30 L / min or more. Effect of the Invention

[0016] According to the present invention, the amount of an element in a non-aqueous solution can be determined with high accuracy. Even if the amount of an element in a non-aqueous solution is small, the amount of the element can be determined with high accuracy. [Brief description of the drawings]

[0017] [Figure 1] 1 is a graph showing the relationship between the material of the container and the Al concentration. [Diagram 2] 1 is a graph showing the relationship between the true value of the Al concentration and the difference from the true value. [Diagram 3] 1 is a graph showing the relationship between the true value and the quantitative value of Al concentration. [Figure 4] 1 is a graph showing the relationship between the flow rate of a carrier gas and BEC. [Diagram 5] 1 is a graph showing the relationship between the flow rate of dilution Ar gas and BEC. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the method for quantifying elements in a non-aqueous solution of this embodiment (hereinafter, for convenience, also referred to as "this quantification method"), a portion of the non-aqueous solution is separated, the separated non-aqueous solution is diluted using Ar gas, and the elements to be analyzed contained in the diluted non-aqueous solution are analyzed using ICP atomic emission spectrometry or ICP mass spectrometry. The present quantification method will be specifically described below. However, the following description is for explaining preferred embodiments of the present invention, and the present invention is not limited to the embodiments described below.

[0019] Preparation of non-aqueous solutions First, a non-aqueous solution to be analyzed is prepared. The non-aqueous solution contains the element to be analyzed and also contains a non-aqueous solvent. For example, an electrolyte obtained by electrolytic extraction of a metal material (electrolytic solution obtained after electrolyzing a metal material) can be given as an example of such a non-aqueous solution. In this case, the above-mentioned sol.A can be obtained by the present quantitative determination method, and therefore the method is highly useful.

[0020] Examples of the electrolyte include non-aqueous solvent electrolytes such as an AA-based (acetylacetone-tetramethylammonium chloride-methanol) electrolyte, an MS-based (methyl salicylate-salicylic acid-tetramethylammonium chloride-methanol) electrolyte, and an MA-based (maleic anhydride-tetramethylammonium chloride-methanol) electrolyte. Non-aqueous solvent-based electrolytes are generally used because they do not dissolve precipitates and can be extracted more stably than aqueous electrolytes (aqueous electrolytes) such as citric acid electrolytes and hydrochloric acid electrolytes.

[0021] From the viewpoint of the industrial usefulness of the information obtained by the present quantitative determination method, the metal material is preferably a steel material. The steel material contains Fe (iron) as a matrix element and further contains a small amount of precipitates and the like.

[0022] When the metallic material is a steel material, it is necessary to electrolyze a large amount of the steel material in an electrolytic solution in order to extract a small amount of precipitates, etc. In this way, an electrolytic solution (electrolytic solution containing the solid-solubilized elements of the steel material) is obtained after electrolysis of the steel material as a non-aqueous solution. When steel materials are electrolyzed in an electrolyte, Fe, which is a matrix element, forms insoluble iron hydroxide, so a complexing agent is added to the electrolyte to capture Fe. For this reason, it is preferable to use an electrolyte in which the amount of Fe electrolysis is adjusted according to the complex retention capacity of the complexing agent. For example, when 10% by volume of acetylacetone is mixed into the electrolyte as a complexing agent, the amount of Fe electrolysis is preferably 2 g / L or less, more preferably 0.1 g / L or less, and even more preferably 0.01 g / L or less, relative to the electrolyte. On the other hand, if the amount of electrolytic Fe is too small, the analytical accuracy decreases, so the amount is preferably 0.0001 g / L or more, and more preferably 0.001 g / L or more.

[0023] <Preparative separation> A part of the non-aqueous solution is separated from the non-aqueous solution to be analyzed using a separation device capable of separating non-aqueous solutions. By the way, the lower the vapor pressure of the non-aqueous solvent (organic solvent) contained in the non-aqueous solution, the more easily it evaporates. Therefore, when a dispensing tool such as an air displacement pipette is used to dispense the non-aqueous solution, the non-aqueous solution tends to drip from the pipette, making it difficult to dispense the solution accurately. Therefore, when dispensing a non-aqueous solution, it is preferable to use a dispensing tool such as a positive displacement pipette, a syringe, etc. A measuring pipette or a burette may be used, and the difference between the marks on the meniscus before and after dispensing may be used as the amount dispensed. When separating, it is preferable to thoroughly stir the non-aqueous solution to obtain a uniform liquid composition before separating. The amount of the solution to be separated may be determined in consideration of the amount required for analysis, and is, for example, 1 mL.

[0024] Dilution Next, the collected non-aqueous solution is diluted with Ar gas. Incidentally, in an apparatus used in ICP analysis (ICP apparatus), a solution to be analyzed is introduced by spraying it into Ar plasma using a carrier gas (for example, Ar gas). At this time, from the viewpoint of the stability of the spray efficiency when the solution for analysis is sprayed into the Ar plasma, it is preferable to dilute the solution for analysis (non-aqueous solution) with water.

[0025] However, when an analytical solution (non-aqueous solution) is diluted with water, the concentration of the target element also decreases at the same time, so if the analytical sensitivity is low, the target element cannot be quantified. For this reason, when analyzing trace elements, it is necessary to introduce a non-aqueous solution that is not diluted with a large amount of water (containing a large amount of non-aqueous solvent) into the Ar plasma.

[0026] However, when a non-aqueous solvent is introduced into the Ar plasma, the Ar plasma may become unstable or disappear, resulting in a decrease in the analytical accuracy of the target element (or the target element may not be analyzed at all). In this case, it is believed that the Ar plasma becomes unstable (or disappears) because it is diluted by the non-aqueous solvent. Therefore, the present inventors have investigated a method for reducing the influence of non-aqueous solvents, which are an obstacle to the analysis of the elements to be analyzed. As a result, they found that the effects of non-aqueous solvents can be reduced by diluting the non-aqueous solution in the carrier gas introduced into the Ar plasma with Ar gas. This is thought to be because replenishing the Ar plasma with diluting Ar gas suppresses the dilution of the Ar plasma, eliminating the instability (or loss) of the Ar plasma.

[0027] At this time, it is preferable to flow Ar gas in a direction perpendicular to the direction of the carrier gas flow to dilute the non-aqueous solution introduced into the Ar plasma. In this case, part of the non-aqueous solution sprayed toward the Ar plasma has its flow path changed by the Ar gas, collides with the inner wall of the torch, and remains there, unable to reach the Ar plasma. This allows an appropriate amount of the target element to be analyzed to be introduced into the Ar plasma while further reducing the effect of the non-aqueous solvent on the Ar plasma.

[0028] In addition, the behavior of excitation and / or emission in Ar plasma may become unstable due to the influence of the non-aqueous solvent. Therefore, in order to reduce the variation in the measured intensity of the element to be analyzed, it is preferable to add an internal standard element to the analysis solution (non-aqueous solution). Examples of the internal standard element include elements such as yttrium and indium.

[0029] When the non-aqueous solution is an electrolyte obtained by electrolyzing a steel sample, the non-aqueous solution contains a large amount of Fe in addition to the element to be analyzed, and the Fe that is not ionized by the Ar plasma is likely to cause clogging of the sampling cone, which reduces the measurement sensitivity of the element to be analyzed (or makes measurement impossible). In this case, the amount of non-aqueous solution introduced into the Ar plasma can be reduced by diluting with Ar gas, improving the ionization efficiency of Fe and reducing the total amount of Fe that reaches the sampling cone, thereby improving the measurement sensitivity of the element to be analyzed.

[0030] With the above measures taken, the concentration of the non-aqueous solvent in the non-aqueous solution is preferably 10% by volume or less, more preferably 5% by volume or less, even more preferably 1% by volume or less, and particularly preferably 0.1% by volume or less.

[0031] <analysis> Next, the elements to be analyzed contained in the non-aqueous solution diluted with Ar gas are analyzed using ICP analysis (ICP atomic emission spectrometry or ICP mass spectrometry). More specifically, a non-aqueous solution diluted with Ar gas is sprayed and introduced into Ar plasma using a carrier gas (e.g., Ar gas), thereby measuring the intensity of the element to be analyzed contained in the non-aqueous solution. The measured intensity is then converted to the concentration of the element to be analyzed using a previously prepared calibration curve, and the amount (mass) of the element to be analyzed contained in the non-aqueous solution is then calculated based on the amount of the sample taken and / or the volume of the non-aqueous solution before a portion is taken for analysis.

[0032] 《Removal of Interfering Elements》 Analytical solutions (non-aqueous solutions) may contain interfering elements that impede the analysis of the target element. Specifically, for example, since the solution for analysis (non-aqueous solution) contains a non-aqueous solvent, elements contained in polyatomic molecules derived from the non-aqueous solvent become interfering elements. In addition, when the analytical solution (non-aqueous solution) is an electrolyte obtained by electrolyzing a metallic material, the electrolyte contains a large amount of matrix elements of the metallic material, and the matrix elements also become interference elements. In the case of a steel material, the matrix element is Fe. The effects of these interfering elements are as follows:

[0033] First, consider the case where the interfering element is an element contained in a polyatomic molecule. The inventors of the present invention have found through their investigations that when a light element such as Al (aluminum) is measured as an element to be analyzed, the concentration indicated may be higher than the actual concentration of the element to be analyzed. This is believed to be due to the presence of polyatomic molecules (polyatomic molecules resulting from non-aqueous solvents) with the same mass number as light elements such as Al (polyatomic ion interference).

[0034] Therefore, the inventors have investigated a method of spraying He gas to reduce the influence of polyatomic molecules. He gas is generally used as a collision gas. It was predicted that by using this method, He gas would collide with polyatomic molecules, preventing them from reaching the detector, and thus enabling the analysis of the target element. As a result of the investigation, it was found that when the element to be analyzed is an element with a large mass number such as Fe, the effect of polyatomic molecules can be reduced by using He gas. However, when the element to be analyzed is a light element such as Al, it was found that the element to be analyzed is also unable to reach the detector.

[0035] The inventors next investigated a method of spraying H2 gas instead of He gas. H2 gas is sometimes used as a reaction gas in mass spectrometers, for example, to react with the target element (or interfering element) to change its mass number in order to extract only the target element. As a result of their investigation, they found that with this method, by using H2, which has a smaller mass number than He, even if H2 gas collides with light elements such as Al, the mass number does not change and the element being analyzed can reach the detector. Therefore, it is preferable to use H2 gas as a gas for removing interfering elements (gas for removing interfering elements).

[0036] Next, a case will be considered in which the solution for analysis (non-aqueous solution) is an electrolyte obtained after electrolysis of a metallic material, and the interfering elements are matrix elements of the metallic material. When a large amount of matrix elements is contained in the electrolytic solution after electrolysis, the matrix elements are ionized, making it difficult to ionize the target element (ionization interference). Alternatively, the matrix elements react with the target element, making it difficult to ionize the target element (chemical interference). This results in a decrease in analytical sensitivity.

[0037] As described above, the influence of such matrix elements can be reduced by diluting the solution for analysis (non-aqueous solution) with Ar gas. In this case, the ICP apparatus used in the ICP analysis method is preferably equipped with a device that can remove interfering elements based on the difference (difference in mass number) between the interfering elements and the element to be analyzed, and is more preferably equipped with a tandem mass spectrometer (a mass spectrometer with two or more stages).

[0038] For example, consider the case where the solution for analysis (non-aqueous solution) is an electrolytic solution obtained after electrolyzing a steel material, and the element to be analyzed is Al. In this case, first, in the first stage mass spectrometer, substances (Al and polyatomic molecules) corresponding to the mass number of Al are passed through, thereby removing Fe, Ar, etc., which have a large mass number difference from Al. Next, in order to remove interfering elements (polyatomic molecules) whose mass numbers are small (or non-existent) from Al, H2 gas is sprayed as described above. After that, in the second stage mass spectrometer, only Al is passed through and reaches the detector. In this way, the element to be analyzed, Al, can be analyzed with higher accuracy.

[0039] Depending on the elements to be analyzed, O2 gas, NH3 gas, He gas, etc. can also be used instead of H2 gas as a gas for removing interfering elements. When the interfering element removing gas selectively reacts with the interfering elements or the element to be analyzed, the mass difference with the element to be analyzed becomes large. Therefore, when the interfering element removing gas selectively reacts with the element to be analyzed, only the substance having the mass number of the element to be analyzed after the reaction is allowed to pass through the second stage mass spectrometer. On the other hand, when the interfering element removal gas selectively reacts with the interfering element, only the substance having the mass number of the element to be analyzed is allowed to pass through the second stage mass spectrometer. In this way, the elements to be analyzed can be analyzed with greater accuracy.

[0040] Carrier gas flow rate Furthermore, the present inventors have investigated a method for reducing the lower limit of quantification as a method for improving analytical sensitivity. One of the simple methods for evaluating the lower limit of quantification is the background equivalent concentration (BEC). By reducing the BEC, analytical sensitivity can be improved even in the case of a low-concentration analytical solution (non-aqueous solution), even when taking into account measurement errors.

[0041] BEC is determined from a calibration curve for calculating the concentration of the element being analyzed from its measured intensity, and is defined by the following formula: BEC[μg / L]=I0 / Slope[L / μg] In the above formula, I0 is the intensity of the analyte element in a solution that does not contain the analyte element, and Slope is the slope of a calibration curve with the vertical axis representing the measured intensity of the analyte element and the horizontal axis representing the concentration of the analyte element.

[0042] As described above, when a non-aqueous solvent (especially a highly volatile non-aqueous solvent such as methanol) is introduced into the Ar plasma, the Ar plasma may disappear. For this reason, it is usually difficult to increase the flow rate of the carrier gas used to introduce the analysis solution (non-aqueous solution) into the Ar plasma. However, the present inventors have found that when the solution for analysis (non-aqueous solution) is diluted with Ar gas for dilution, the above problem is unlikely to occur even if the flow rate of the carrier gas is increased.

[0043] FIG. 4 is a graph showing the relationship between the flow rate of the carrier gas and the BEC. The graph in FIG. 4 reveals the following. First, as the carrier gas flow rate increases, the BEC value drops sharply. However, when the carrier gas flow rate is 0.30 L / min or higher, the BEC value drops gradually. Then, when the carrier gas flow rate is 0.40 L / min, the BEC value becomes almost constant. For this reason, a carrier gas flow rate of 0.30 L / min or higher is preferable, and 0.40 L / min or higher is more preferable. Although there is no particular upper limit, the flow rate of the carrier gas is preferably 0.50 L / min or less, since an excessive supply of the carrier gas will not provide a BEC reduction effect.

[0044] <Flow rate of Ar gas for dilution> Furthermore, the present inventors investigated the relationship between the flow rate of dilution Ar gas and BEC. FIG. 5 is a graph showing the relationship between the flow rate of dilution Ar gas and the BEC. 5, it can be seen that the flow rate of the dilution Ar gas is less likely to affect the BEC value if it is in the range of at least 0.47 to 0.67 L / min. For this reason, the flow rate of the dilution Ar gas is preferably 0.47 to 0.67 L / min.

[0045] <Creating a calibration curve> As described above, this quantitative determination method can eliminate the influence of interfering elements, and therefore a calibration curve can be created using a commercially available standard solution (aqueous solution) as the calibration curve solution. On the other hand, the present inventors have found that the analytical error caused by the influence of interfering elements can be reduced by preparing a calibration curve using a calibration curve solution adjusted to contain the same amount of interfering elements as the analytical solution (non-aqueous solution). This is presumably due to the effect of combining the spray efficiency of the calibration curve solution with the analytical solution (non-aqueous solution). In particular, when analyzing trace elements, it is preferable to prepare a calibration curve in this manner.

[0046] <Volume Measurement> In this quantitative determination method, the volume of the non-aqueous solution to be analyzed may be measured, which makes it possible to determine the amount (mass) of elements contained in the non-aqueous solution even when the volume of the non-aqueous solution is unknown. The method for measuring the volume of the non-aqueous solution is not particularly limited. For example, a non-aqueous solution contained in a container (conveniently called "Container 1") is transferred in its entirety to a container (conveniently called "Container 2") marked with a volumetric scale. At this time, the non-aqueous solution adhering to Container 1 is washed with a solvent constituting this non-aqueous solution, and the washing liquid resulting from this washing is also added to Container 2. Thereafter, when the position of the meniscus of the non-aqueous solution in the container 2 coincides with any of the marks on the container 2, the value on that mark is taken as the volume of the non-aqueous solution. On the other hand, if the meniscus of the non-aqueous solution in container 2 does not match any of the scales, the solvent that constitutes the non-aqueous solution is added until the meniscus of the non-aqueous solution matches any of the scales, and the value of the scale where the meniscus matches is taken as the volume of the non-aqueous solution. Container 1 and container 2 may be the same container. The container 2 is not particularly limited as long as it is a container with a scale indicating the volume, and examples thereof include a graduated cylinder and a graduated flask.

[0047] <Materials of equipment that comes into contact with non-aqueous solutions> When the present inventors analyzed the Al concentration in the electrolyte of a steel material using this quantitative method, they found that the Al concentration was sometimes measured to be higher than the actual concentration. To investigate the cause, we prepared an electrolyte (10% by volume acetylacetone-methanol) and several containers made of different materials. The containers were made of four different materials: polypropylene (PP), borosilicate glass, quartz glass, and perfluoroalkoxyethylene (PFA), a fluororesin. Each container was filled with 100 mL of electrolyte, covered, and left for 2 days. The Al concentration in the electrolyte in each container was then determined using this quantitative method. The results are shown in Figure 1.

[0048] Figure 1 is a graph showing the relationship between the container material and the Al concentration. As shown in the graph in Figure 1, it was found that the Al concentration differed depending on the container material. Specifically, the Al concentration decreased in the following order: PP > borosilicate glass > quartz glass > PFA. This is presumably because the components in the electrolyte corroded the PP and other materials that make up the container, causing the Al components to dissolve into the electrolyte. At this time, it is presumed that because the quartz glass contains few impurities such as Al, the amount of Al component eluted into the electrolyte was small. In addition, fluororesins such as PFA have excellent properties such as chemical resistance, so they are less likely to be corroded by the electrolyte, and it is presumed that less Al component was dissolved into the electrolyte.

[0049] For this reason, in this quantitative method, particularly when the element to be analyzed is a trace amount of Al, the material of the instrument that comes into contact with the non-aqueous solution is preferably at least one selected from the group consisting of borosilicate glass, quartz glass, and fluororesin, more preferably at least one selected from the group consisting of quartz glass and fluororesin, and even more preferably fluororesin. Examples of fluororesins include perfluoroalkoxyethylene (PFA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and ethylene tetrafluoroethylene (ETFE).

[0050] Specific examples of devices that come into contact with non-aqueous solutions during preparation, collection, dilution, and analysis of the non-aqueous solutions include containers such as beakers, measuring flasks, measuring cylinders, and sample cups; collection devices such as measuring pipettes and Komagome pipettes; and the like. When the non-aqueous solution is an electrolyte, the container is in contact with the electrolyte for a long period of time, and therefore the container (electrolytic cell) used for electrolysis is preferably made of the above-mentioned materials. That is, in the present quantitative determination method, it is more preferable that the materials of all the tools that come into contact with the non-aqueous solution (surfaces of these tools that come into contact with the non-aqueous solution) are the above-mentioned materials. EXAMPLES

[0051] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples described below.

[0052] Test 1 In Test 1, the effect of H2 gas spray on the analytical accuracy in this quantitative method was evaluated. First, as an analytical solution (non-aqueous solution), a 10 vol% methanol solution was prepared in which the element to be analyzed was Al and the non-aqueous solvent was methanol, with the Al concentration adjusted to 0, 10, 20, 30, 40, or 50 μg / L. The analytical solution was prepared by adding a commercially available Al standard solution to the 10 vol% methanol solution so as to obtain the desired Al concentration. Next, using a commercially available Al standard solution (aqueous solution), the intensity of a substance having the mass number of Al (27) was measured in an ICP apparatus, and the relationship between the concentration of the Al standard solution and the Al intensity was plotted to create Al calibration curve 1. Thereafter, the Al intensity of each analytical solution was measured in an ICP apparatus according to the following procedure, and the Al concentration in each analytical solution was determined using Al calibration curve 1. The ICP device used was an ICP-MS (ICP mass spectrometer) equipped with a tandem mass spectrometer.

[0053] First, the measurement procedure for Example 1a (with H2 gas spray) will be described. The analytical solution was atomized using a carrier gas (Ar gas) and introduced into the Ar plasma. At this time, Ar gas for dilution was introduced from a direction perpendicular to the carrier gas just before the atomized analytical solution was introduced into the Ar plasma. The element to be analyzed (such as Al) in the analysis solution introduced into the Ar plasma is ionized and introduced into a mass spectrometer. The mass number of the first stage mass spectrometer was set to 27, the mass number of Al, and Al and polyatomic molecules corresponding to the mass number of 27 were passed through. Then, H2 gas was sprayed to remove the polyatomic molecules. Next, the mass number of the second stage mass spectrometer was set to 27, the mass number of Al, and Al was passed through, and the Al intensity was measured in the detector.

[0054] Next, the measurement procedure for Example 1b (without H2 gas spraying) will be explained. The Al intensity was measured in the same manner as in Example 1a above, except that H2 gas was not sprayed after passing through the first stage mass spectrometer.

[0055] In both Examples 1a and 1b, the Al concentration in each analytical solution was calculated from the measured Al intensity, as described above, and the difference from the true value was also calculated. The results are shown in FIG. Fig. 2 is a graph showing the relationship between the true value of the Al concentration and the difference from the true value. Fig. 2 shows only the results when the true value of the Al concentration is 0, 10, and 20 μg / L, as a representative example. As shown in the graph in Figure 2, in Example 1b (without H2 gas spraying), a maximum error of +22.5% occurred from the true value. In contrast, in Example 1a (with H2 gas spraying), a maximum error of +2.3% occurred from the true value. This shows that the quantitative accuracy of Al concentration is improved by H2 gas spraying.

[0056] Test 2 In Test 2, the analytical accuracy of this quantitative method was evaluated when the electrolytic solution obtained after electrolyzing a metal material was used as the analytical solution (non-aqueous solution). In the following, the electrolytic solution obtained after electrolyzing a steel material containing Al was used as the analytical solution.

[0057] First, pure iron (Myron UHP, manufactured by Toho Zinc Co., Ltd.) was prepared as the metal material (sample) to be electrolyzed. The sample was washed and dried before electrolysis, and then its mass was measured. Next, an AA electrolyte solution (10% by volume of acetylacetone-2% by volume of tetramethylammonium chloride-methanol) was prepared as an electrolyte solution. The sample was electrolyzed in an electrolytic cell containing 50 mL of electrolyte, with the electrolysis conditions set to achieve the desired amount of electrolyte. The electrolytic sample was then slowly pulled out of the electrolyte, and the electrolyte adhering to the sample was washed away with unused electrolyte, and the electrolytic sample was then recovered in the electrolytic cell. The electrolytic sample was immersed in methanol and ultrasonically cleaned in order to remove deposits from the sample surface. After the deposits were removed, the sample was dried, and then its mass was measured. The amount of electrolysis was calculated from the difference in mass of the sample before and after electrolysis, which was 0.1 g.

[0058] Next, the electrolyte in the electrolytic cell was transferred into the measuring cylinder. The electrolyte adhering to the inside of the electrolytic cell was also poured into the measuring cylinder using unused electrolyte. Next, the meniscus of the electrolyte in the measuring cylinder was adjusted to the 100 mL mark of the measuring cylinder by adding unused electrolyte. After the adjustment, the measuring cylinder was covered and shaken up and down to stir the electrolyte in the measuring cylinder. From the stirred electrolyte, 1 mL of electrolyte was dispensed into a cup with a lid using a measuring pipette. Next, a commercially available Al standard solution (aqueous solution) was added to the dispensed electrolyte so that the Al concentration was 0, 10, 20, 30, 40, or 50 μg / L, and finally the volume was adjusted to 10 mL with pure water to prepare a solution for analysis. The prepared analytical solution contained the interfering element Fe and methanol as a non-aqueous solvent, and had a known Al concentration, so it was also used as a calibration curve solution for Al calibration curve 2, which will be described later.

[0059] The Al intensity of each analytical solution was measured using ICP-MS. The procedure for measuring the Al intensity was the same as in Example 1a (with H2 gas spraying) and Example 1b (without H2 gas spraying) of the above Test 1. The first-stage mass spectrometer was also able to eliminate Fe, an interfering element contained in the analytical solution.

[0060] Next, the Al concentration in each analytical solution was determined based on the measured Al intensity. When calculating the Al concentration from the Al intensity, in addition to the Al calibration curve 1 prepared in the above test 1, the Al calibration curve 2 prepared by the following procedure was also used. The Al calibration curve 2 was prepared by measuring the Al intensity of each analytical solution under the same conditions as in Example 1a of Test 1 above (with H2 gas spraying) and plotting the relationship between the measured Al intensity and the Al concentration of each analytical solution.

[0061] FIG. 3 is a graph showing the relationship between the true value and the quantitative value of the Al concentration. When the Al intensity was measured without H2 gas spraying and the Al concentration was quantified using Al calibration curve 1, the measurement error was a maximum of 24.4%. On the other hand, when the Al intensity was measured with H2 gas spray and the Al concentration was quantified using Al calibration curve 1, the measurement error was a maximum of 6.7%. This indicates that the quantitative accuracy of Al concentration is improved by H2 gas spraying.

[0062] Furthermore, when the Al intensity was measured with H2 gas spray and the Al concentration was quantified using Al calibration curve 2, the measurement error was a maximum of 3.1%. From this, it was found that by creating a calibration curve (Al calibration curve 2) using a calibration curve solution prepared to contain the same amount of interfering elements as the analytical solution, and using this, the Al concentration can be quantified with even greater accuracy.

[0063] In this case, the square of the correlation coefficient was 1.0, and the quantitative value had a good correlation with the true value.

[0064] The Al concentration of the blank solution was quantified, and the lower limit of quantification (10 x standard deviation) was calculated to be 1 μg / L, indicating that trace amounts of Al can be quantified. The analytical solution contained about 100 mg / L of the interfering element Fe. Considering the lower limit of quantification of the target element Al, the mass ratio of the interfering element to the target element was 1.0 × 10 5 It was found that even when aluminum is present in large quantities, trace amounts of aluminum can be measured with high accuracy.

[0065] All of the instruments used in Test 2 were made of fluororesin (the same applies to Test 3 described below). Test 2 was carried out within one day.

[0066] Test 3 The test was carried out in the same manner as in Test 2. However, a commercially available S standard solution (aqueous solution) was used instead of the Al standard solution to prepare a calibration curve solution. O2 gas is used as the cell gas for the collision reaction cell (CRC) installed in the ICP device. 32 S + By reacting with ions 32 S16 O + Therefore, the mass number of the first mass spectrometer was set to 32, and the mass number of the second mass spectrometer was set to 48. A calibration curve was created with the carrier gas flow rate set to 0.24, 0.29, 0.34, 0.39, or 0.44 L / min. The dilution Ar gas flow rate was set to 0.57 L / min. The BEC was calculated from the resulting calibration curve. The results are shown in the graph in Figure 4. From the graph in Figure 4, it was found that the BEC can be reduced (i.e., the lower limit of quantification can be reduced) by increasing the flow rate of the carrier gas. Specifically, for example, it was found that the BEC value can be reduced to 10 μg / L by setting the flow rate of the carrier gas to 0.30 L / min.

Claims

1. 1. A method for quantifying an element in a non-aqueous solution, comprising the steps of: A portion of the non-aqueous solution is collected, The collected non-aqueous solution is introduced into Ar plasma by spraying using a carrier gas; Ar gas is caused to flow in a direction perpendicular to the flow direction of the carrier gas, and the non-aqueous solution introduced into the Ar plasma is diluted while changing a part of the flow path of the non-aqueous solution; A method for quantifying elements in a non-aqueous solution, comprising analyzing the elements to be analyzed contained in the diluted non-aqueous solution using ICP atomic emission spectrometry or ICP mass spectrometry.

2. The method for quantifying elements in a non-aqueous solution according to claim 1 , further comprising removing interfering elements contained in the non-aqueous solution when analyzing the elements to be analyzed contained in the non-aqueous solution.

3. The method for quantifying elements in a non-aqueous solution according to claim 1 or 2, wherein the non-aqueous solution is an electrolytic solution obtained after electrolyzing a metal material.

4. 3. The method for quantifying elements in a non-aqueous solution according to claim 1, wherein the material of an instrument that comes into contact with the non-aqueous solution is at least one material selected from the group consisting of borosilicate glass, quartz glass, and fluorine-based resins.

5. The method for quantifying an element in a non-aqueous solution according to claim 1 or 2, wherein the element to be analyzed contained in the non-aqueous solution is Al.

6. 3. The method for quantifying elements in a non-aqueous solution according to claim 1, wherein the flow rate of the carrier gas is 0.30 L / min or more.

Images