Ph adjuster for mobile phase solvent, mobile phase solution, liquid chromatography-mass spectrometry kit, and analysis method for analytical sample

Abstract

This pH adjuster for a mobile phase solvent in a liquid chromatograph-tandem mass spectrometry apparatus includes a primary amine.

Description

pH adjuster for mobile phase solvent, mobile phase solution, liquid chromatography-mass spectrometry kit, and method for analyzing analytical samples

[0001] The present invention relates to a pH adjuster for a mobile phase solvent, a mobile phase solution, a liquid chromatography-mass spectrometry kit, and a method for analyzing an analytical sample.

[0002] When analyzing a sample using a liquid chromatograph-tandem mass spectrometer (hereinafter sometimes referred to as an "LC-MS analyzer"), an acidic or basic mobile phase is used to improve the separation performance and detection sensitivity of substances contained in the sample. Conventionally, ammonia, alkali metal hydroxides, secondary amines, tertiary amines, etc. have been used as pH adjusters to make the mobile phase basic.

[0003] For example, Non-Patent Document 1 discloses that when preparing a basic mobile phase, alkali metal hydroxides, ammonia, diethylamine, and triethylamine are usually selected as additives.

[0004] Barry E. Boyes, Michael W. Dong, LCGC North America, 2018, 10, 752-768.

[0005] However, because ammonia volatilizes at room temperature, when ammonia is used as a pH adjuster for the mobile phase, the ammonia concentration in the mobile phase tends to decrease over time. Therefore, when an analysis is performed using an LC-MS analyzer using a mobile phase containing ammonia, the detection sensitivity tends to decrease over time. Furthermore, because alkali metal hydroxides are non-volatile, when alkali metal hydroxides (e.g., NaOH, KOH, etc.) are used as the pH adjuster, they precipitate in the analyzer and cannot be used.

[0006] Furthermore, diethylamine and triethylamine have high proton affinity and are easily ionized, so when diethylamine or triethylamine is used as a pH adjuster in the mobile phase in an LC-MS analysis, the detection sensitivity in the positive mode tends to decrease.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a pH adjuster for a mobile phase solvent in an LC-MS analyzer, which has excellent detection sensitivity of the analyzer and can adjust the mobile phase to basicity.

[0008] As a result of intensive research, the inventors discovered that adding a primary amine as a pH adjuster to a mobile phase solvent can make the mobile phase solvent basic while improving the detection sensitivity of the above-mentioned analytical device, and thus completed the present invention.

[0009] A first aspect of the present invention relates to a pH adjuster for a mobile phase solvent in a liquid chromatograph-tandem mass spectrometer, the pH adjuster comprising a primary amine.

[0010] A second aspect of the present invention relates to a mobile phase solution for a liquid chromatograph-tandem mass spectrometer, comprising: the pH adjuster according to the first aspect; and a solvent.

[0011] A third aspect of the present invention relates to a kit for liquid chromatography-mass spectrometry, comprising: the pH adjuster according to the first aspect; and a solvent.

[0012] A fourth aspect of the present invention relates to a method for analyzing an analytical sample, comprising: a preparation step of preparing the analytical sample; a separation step of separating the analytical sample into components using a liquid chromatograph; and an analysis step of analyzing the separated components using a mass spectrometer, wherein the mobile phase of the liquid chromatograph in the separation step contains the pH adjuster according to the first aspect.

[0013] According to the present invention, it is possible to provide a pH adjuster for a mobile phase solvent in an LC-MS analyzer, which has excellent sensitivity for the analyzer and can adjust the mobile phase to a basic pH.

[0014] Figure 1 is a graph showing the peak area ratios when LC-MS analysis was performed using mobile phase solutions prepared a certain amount of time ago in Experimental Example 1. The horizontal axis shows the time elapsed after preparation of the mobile phase, and the vertical axis shows the ratio of the area value based on the peak area of ​​glucose at 0 h. Figure 2 is a graph showing the peak areas when LC-MS analysis was performed using each mobile phase solution in Experimental Example 2. The vertical axis shows the peak area value of glucosamine.

[0015] An embodiment of the present invention (hereinafter referred to as "this embodiment") will be described below. However, this embodiment is not limited thereto. In this specification, the notation in the form of "A to Z" means the upper and lower limits of a range (i.e., A or more and Z or less), and when no unit is specified for A and a unit is specified only for Z, the unit of A and the unit of Z are the same.

[0016] In this embodiment, "normal temperature" means a temperature of 18° C. or higher and 28° C. or lower. In this embodiment, "normal pressure" means an atmospheric pressure of 1013 hPa.

[0017] <pH Adjuster> A first aspect of this embodiment is a pH adjuster for a mobile phase solvent in a liquid chromatograph-tandem mass spectrometer, which includes a primary amine.

[0018] In this embodiment, the term "pH adjuster" refers to an agent for changing the proton concentration of a target solvent or solution. The pH adjuster according to this embodiment is used to make the mobile phase solvent basic. The pH adjuster includes a primary amine.

[0019] <Primary Amine> In this embodiment, a primary amine refers to an organic compound in which one hydrogen atom of ammonia has been substituted with a hydrocarbon group. Examples of primary amines include aliphatic amines, aromatic amines, alicyclic amines, and alkoxyalkylamines. Examples of aliphatic amines include methylamine, ethylamine, propylamine, butylamine, and allylamine. Examples of aromatic amines include aniline and catecholamine. Examples of alicyclic amines include cyclopropylamine and cyclobutylamine. Examples of alkoxyalkylamines include 2-methoxyethylamine and 3-methoxypropylamine. The primary amines may be synthesized by known methods or may be commercially available. In this embodiment, the primary amine preferably includes at least one compound selected from the group consisting of alicyclic amines and alkoxyalkylamines. In one aspect of this embodiment, the primary amine more preferably includes at least one compound selected from the group consisting of cyclopropylamine and 2-methoxyethylamine.

[0020] In this embodiment, the acid dissociation constant (hereinafter, sometimes referred to as "pKa") means the equilibrium constant defined by the following formula 2 in the acid dissociation equilibrium reaction of a primary amine shown in the following formula 1. The acid dissociation constant is measured at room temperature and normal pressure. In formula 1, R-NH ２ , R-NH － and H ＋ and represent the general formula of a primary amine (wherein R represents a hydrocarbon group), the conjugate base of the primary amine, and a proton, respectively. － ] and [R-NH ２ ] are R-NH － Concentration of R-NH ２ The concentration of R-NH ２ ⇔R-NH － +H ＋ ...(Formula 1) pKa=pH-(log １０ ([R-NH － ] / [R-NH ２ ]))...(Formula 2)

[0021] In this embodiment, the acid dissociation constant of the primary amine is preferably 8.5 or greater from the viewpoint of preparing a basic mobile phase. Examples of primary amines having an acid dissociation constant of 8.5 or greater include methylamine (pKa: 10.6), ethylamine (pKa: 10.7), allylamine (pKa: 9.5), cyclopropylamine (pKa: 9.1), and 2-methoxyethylamine (pKa: 9.2).

[0022] In this embodiment, the proton affinity of the primary amine is preferably 930 kJ / mol or less from the viewpoint of suppressing a decrease in sensitivity in the positive mode. Examples of primary amines having a proton affinity of 930 kJ / mol or less include methylamine (899.0 kJ / mol), ethylamine (912.0 kJ / mol), allylamine (909.5 kJ / mol), 2-methylallylamine (917.5 kJ / mol), cyclopropylamine (904.7 kJ / mol), and 2-methoxyethylamine (928.6 kJ / mol).

[0023] The boiling point is the temperature at which the saturated vapor pressure of a liquid becomes equal to the external pressure. The boiling point is measured under ambient conditions of room temperature and pressure.

[0024] In this embodiment, the boiling point of the primary amine is preferably 45° C. or higher and 200° C. or lower, from the viewpoints of applicability to LC-MS analysis and of being less likely to volatilize from the mobile phase. Examples of primary amines having a boiling point of 45° C. or higher and 200° C. or lower include allylamine (boiling point: 53° C.), cyclopropylamine (boiling point: 50° C.), and 2-methoxyethylamine (boiling point: 90° C.).

[0025] In one aspect of this embodiment, the primary amine preferably includes a compound having an acid dissociation constant of 8.5 or more, a proton affinity of 930 kJ / mol or less, and a boiling point of 45° C. or more and 200° C. or less. In this embodiment, examples of primary amines that satisfy the above acid dissociation constant, proton affinity, and boiling point include cyclopropylamine, 2-methoxyethylamine, and allylamine.

[0026] In this embodiment, the pH adjuster may be a primary amine undiluted solution itself, or may be in the form of a highly concentrated solution.

[0027] Conventionally, ammonia, alkali metal hydroxides, secondary amines, tertiary amines, and the like have been used as pH adjusters to make the mobile phase basic. However, because ammonia is volatile, the ammonia concentration in the mobile phase decreases over time, which in turn tends to decrease the detection sensitivity of mass spectrometry over time. Therefore, it is unsuitable for long-term continuous analysis in LC-MS analysis. Furthermore, because alkali metal hydroxides are non-volatile, they precipitate in the analytical device and cannot be used. The primary amine used in this embodiment is liquid and non-volatile. Therefore, long-term continuous analysis in LC-MS analysis is possible. Furthermore, it does not precipitate in the analytical device.

[0028] On the other hand, diethylamine and triethylamine have high proton affinities, 952.4 kJ / mol and 981.8 kJ / mol, respectively. Therefore, they tend to ionize themselves easily, which in turn tends to reduce the detection sensitivity in the positive ion mode of mass spectrometry. The primary amines used in this embodiment have lower proton affinities than secondary amines and tertiary amines. Therefore, the analyte tends to be preferentially ionized, enabling mass spectrometry with good detection sensitivity.

[0029] <Liquid chromatograph-tandem mass spectrometer> A liquid chromatograph-tandem mass spectrometer is a device in which the column outlet of a liquid chromatograph is connected to the sample introduction section of a mass spectrometer.

[0030] A liquid chromatograph is a device used to perform chromatography, which uses a liquid as the mobile phase. Chromatography is a method of separating substances by utilizing the difference in affinity between the stationary phase and the mobile phase. Details are explained in the "Analysis Method" section below.

[0031] A tandem mass spectrometer is a device that includes a sample introduction unit, an ionization unit, a mass analysis unit, a detection unit, a vacuum pumping unit, and a data processing unit. The ionization unit ionizes the substances separated by the liquid chromatograph using an ionization method. The mass analysis unit detects the mass-to-charge ratio of the ionized substances as they pass through a magnetic or electric field. Details will be explained in the "Analysis Method" section below.

[0032] <Mobile Phase Solvent> In this embodiment, the mobile phase solvent refers to a solvent used as the mobile phase in the liquid chromatograph. Here, the mobile phase refers to a liquid that is passed through the stationary phase in order to separate the components of an analytical sample in liquid chromatography. The mobile phase solvent according to this embodiment is not particularly limited as long as it can dissolve the pH adjuster, and any known solvent used in the mobile phase of a liquid chromatograph can be used. Examples of mobile phase solvents include water, methanol, acetonitrile, ethanol, 2-propanol, acetone, and tetrahydrofuran. In one aspect of this embodiment, the mobile phase solvent preferably contains at least one solvent selected from the group consisting of water, methanol, acetonitrile, ethanol, 2-propanol, acetone, and tetrahydrofuran.

[0033] <Mobile Phase Solution> A second aspect of this embodiment is a mobile phase solution for a liquid chromatograph-tandem mass spectrometer, comprising: the pH adjuster according to the first aspect; and a solvent (mobile phase solvent).

[0034] Specific aspects of the pH adjuster and the solvent are as described in Aspect 1. In one aspect of this embodiment, the mobile phase solution can also be understood as "a solution in which the pH adjuster is dissolved in the solvent."

[0035] In this embodiment, the concentration of the primary amine is preferably 1 mM or more and 100 mM or less in the mobile phase solution, from the viewpoint of performing analysis with high sensitivity using the LC-MS analyzer.

[0036] <Liquid Chromatography-Mass Spectrometry Kit> A third aspect of the present embodiment is a liquid chromatography-mass spectrometry kit including: the pH adjuster according to the first aspect; and a solvent (mobile phase solvent).

[0037] Specific aspects of the pH adjuster and the solvent are as described in Aspect 1. In one aspect of this embodiment, the mobile phase solution can also be understood as "a solution in which the pH adjuster is dissolved in the solvent."

[0038] In this embodiment, the liquid chromatography-mass spectrometry kit may be in a state in which the pH adjuster and the mobile phase solvent are contained in separate containers, or in a state in which they are contained in a single container (in the state of the mobile phase solution).

[0039] The liquid chromatography-mass spectrometry kit may further include one or more items selected from the group consisting of a sample tube, a bottle for a mobile phase, a support for a stationary phase, and an instruction manual for the user of the kit.

[0040] <Stationary Phase Carrier> In one aspect of this embodiment, the liquid chromatography-mass spectrometry kit preferably further includes a stationary phase carrier. Here, the stationary phase refers to a phase that exhibits interaction with each component contained in an analytical sample by utilizing affinity, hydrophobicity, etc. in liquid chromatography, and does not move. The stationary phase carrier refers to a carrier used as the stationary phase. As the carrier, a solid, a gel-like substance, etc. can be used. In this embodiment, the liquid chromatography-mass spectrometry kit may include the stationary phase carrier itself, or may include a column packed with the stationary phase carrier.

[0041] In this embodiment, the applicable pH range of the stationary phase carrier is preferably 1 or more and 14 or less, from the viewpoint of preventing deterioration of the stationary phase carrier due to the basic mobile phase. There are no particular limitations as long as the pH is within the applicable range, and any known stationary phase carrier can be used.

[0042] In one aspect of this embodiment, the stationary phase support preferably includes at least one selected from the group consisting of silica gel, polymer gel, and porous graphite carbon.

[0043] <Analysis Method> A fourth aspect of the present embodiment is a method for analyzing an analysis sample, comprising: a preparation step of preparing the analysis sample; a separation step of separating the analysis sample using a liquid chromatograph; and an analysis step of analyzing the separated analysis sample with a mass spectrometer, wherein a mobile phase of the liquid chromatograph in the separation step comprises the pH adjuster according to the first aspect.

[0044] <Preparation Step> In this step, an analytical sample is prepared. In this embodiment, the analytical sample refers to a sample to be subjected to the separation step described below. The analytical sample is not particularly limited and may be a biological sample (e.g., a biological tissue-derived sample or a blood-derived sample) or a food-derived sample. In one aspect of this embodiment, the biological sample or food-derived sample may be pretreated by a known pretreatment method to prepare the analytical sample. Examples of such pretreatment include sample homogenization, protein removal, and extraction of the target components.

[0045] The analytical sample in this embodiment preferably contains, as the component to be analyzed, at least one compound selected from the group consisting of monosaccharides, acidic compounds, and basic compounds.

[0046] In this embodiment, the monosaccharide has the general formula C ｎ (H ２ O) ｎ (n is an integer of 3 to 6) and derivatives thereof. Examples of the monosaccharide include aldoses such as glucose, mannose, and galactose, and ketoses such as fructose, xylulose, and ribulose. ｎ (H ２ O) ｎDerivatives of the compound represented by the formula (I) include, for example, sugar acids, sugar alcohols, and amino sugars (including amino sugars in which the amino group is acetylated). Examples of the sugar acids include gluconic acid and glucuronic acid. Examples of the sugar alcohols include sorbitol. Examples of the amino sugars include glucosamine (GlcN). Furthermore, examples of the amino sugars in which the amino group is acetylated include N-acetylglucosamine (GluNAC), N-acetylmannosamine (ManNAC), and N-acetylgalactosamine (GalNAC).

[0047] In this embodiment, an acidic compound refers to a compound having acidic properties. The acidic compound can also be understood as a "compound that releases hydrogen ions in an aqueous solution." The acidic compound in this embodiment is not particularly limited, and known acidic compounds can be used. Examples of the acidic compound include compounds having a phosphate group, compounds having a carboxyl group, and compounds having a sulfate group.

[0048] In this embodiment, the basic compound refers to a compound having basic properties. The basic compound can also be understood as a "compound that accepts hydrogen ions in an aqueous solution." The basic compound in this embodiment is not particularly limited, and any known basic compound can be used. Examples of the basic compound include compounds having an amino group.

[0049] <Separation Step> In this step, the analytical sample is separated into its components using a liquid chromatograph. Liquid chromatographs (LC) utilize the differences in the affinities of the components in the analytical sample for the mobile phase and the stationary phase to separate the components and elute them at different retention times. The type of liquid chromatograph is not limited as long as it can separate the components to be analyzed with the desired accuracy so that they can be separated and detected by a mass spectrometer. Examples of liquid chromatographs that can be used include nano LC, micro LC, high-performance liquid chromatographs (HPLC), and ultra-high-performance liquid chromatographs (UHPLC).

[0050] In this embodiment, the mobile phase is not particularly limited as long as it contains the pH adjuster, and any of the solvents listed above as the mobile phase solvents can be used.

[0051] In this embodiment, the stationary phase is not particularly limited, and the above-mentioned stationary phase carriers can be used.

[0052] <Analysis step> In this step, the separated components are analyzed using a mass spectrometer. The separated components preferably contain at least one compound selected from the group consisting of monosaccharides, acidic compounds, and basic compounds.

[0053] In this embodiment, when analyzing the basic compounds, the analysis is preferably performed in positive mode. In this embodiment, when analyzing the monosaccharides and acidic compounds, the analysis is preferably performed in negative mode. In this embodiment, when the elution time of the target component is known in advance in the separation by liquid chromatography, the ionization mode may be appropriately set to positive mode or negative mode based on the elution time.

[0054] In other words, it is preferable that the analytical sample contains a basic compound and the analysis step is performed in a positive mode, and it is also preferable that the analytical sample contains an acidic compound or a monosaccharide and the analysis step is performed in a negative mode.

[0055] In this embodiment, the ionization method used by the mass spectrometer is not particularly limited, and any known ionization method can be used, such as electrospray ionization (ESI) or nano-electrospray ionization (nano-LSI).

[0056] In this embodiment, the mass analyzer included in the tandem mass analyzer is not particularly limited and may be any known mass analyzer. Examples of the tandem mass analyzer including the mass analyzer in this embodiment include a Fourier transform mass analyzer, a time-of-flight (Q-TOF) mass analyzer, a triple quadrupole mass analyzer, and a single quadrupole mass analyzer.

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] Experimental Example 1 Preparation of Analytical Sample (Preparation Step) In Experimental Example 1, an analytical sample to be subjected to LC-MS analysis was prepared. Specifically, glucose was dissolved in water to a final concentration of 100 μM to prepare the analytical sample.

[0059] <Preparation of Mobile Phase Solutions> The following mobile phase solutions 11 to 13 were prepared as mobile phase solutions in Experimental Example 1. Here, cyclopropylamine (pKa: 9.1, boiling point: 50°C, manufactured by Tokyo Chemical Industry Co., Ltd.) and 2-methoxyethylamine (pKa: 9.2, boiling point: 90°C, manufactured by Tokyo Chemical Industry Co., Ltd.) correspond to the pH adjuster in this embodiment. Mobile phase solution 11 corresponds to a comparative example. Mobile phase solutions 12 and 13 correspond to examples. Mobile phase solution 11: 0.1 mass % NH ３ Aqueous Solution Mobile Phase Solution 12: 10 mM cyclopropylamine aqueous solution Mobile Phase Solution 13: 5 mM 2-methoxyethylamine aqueous solution

[0060] <LC-MS Analysis (Separation Step, Analysis Step)> In Experimental Example 1, the prepared mobile phase solutions 11, 12, and 13 were stored at room temperature and normal pressure for 0 hours, 24 hours, and 48 hours, respectively. 100 μM glucose was injected into each of the stored mobile phase solutions as mobile phase A, and LC-MS analysis was performed. The LC analysis conditions and MS analysis conditions are shown below. The results are shown in FIG. 1.

[0061] (LC analysis conditions) Column: porous graphite carbon column (Supel Carbon LC (2.1 x 150 mm), pH 1-14) Mobile phase: mobile phase A (mobile phase solution 11, 12, or 13) Mobile phase B (acetonitrile / 2-propanol 1 / 1 mixture) Gradient settings: Flow rate: 0.2 mL / min Column temperature: 40°C Sample injection amount: 1 μl

[0062] (MS analysis conditions) Ionization mode: Positive mode / negative mode simultaneous analysis Analysis mode: MRM Nebulizer gas flow rate: 10 L / min Heating gas flow rate: 5 L / min Drying gas flow rate: 15 L / min Interface temperature: 200°C DL temperature: 150°C Heat block temperature: 400°C

[0063] FIG. 1 is a graph showing the peak area ratio when LC-MS analysis is performed using a mobile phase solution that has been prepared for a certain period of time. The horizontal axis shows the time that has passed since the mobile phase was prepared, and the vertical axis shows the ratio of the area value when the peak area of ​​glucose at 0 h is used as the reference. From the results in FIG. 1, it was found that in the analysis using mobile phase solution 11 (comparative example), the area ratio decreased significantly as time passed after the mobile phase solution was prepared. With mobile phase solution 11, the area ratio of NH ３ It is believed that the detection sensitivity decreased due to the evaporation of the mobile phase solution. On the other hand, in the analysis using mobile phase solutions 12 and 13 (Examples), it was found that the decrease in area ratio was suppressed even after the passage of time after the preparation of the mobile phase solution. From the above results, it was found that mobile phase solutions 12 and 13 (Examples) have excellent detection sensitivity even after the passage of time after the preparation of the mobile phase solution. It was also suggested that mobile phase solutions 12 and 13 (Examples) are suitable for long-term continuous analysis in LC-MS analysis.

[0064] Experimental Example 2 Preparation of Analytical Sample (Preparation Step) In Experimental Example 2, an analytical sample to be subjected to LC-MS analysis was prepared. Specifically, glucosamine was dissolved in water to a final concentration of 100 μM to prepare the analytical sample.

[0065] <Preparation of Mobile Phase Solutions> The following mobile phase solutions 21 to 23 were prepared as mobile phase solutions in Experimental Example 2. Here, cyclopropylamine and 2-methoxyethylamine correspond to the pH adjuster in this embodiment. Mobile phase solution 21 corresponds to a comparative example. Mobile phase solutions 22 and 23 correspond to examples. Mobile phase solution 21: 1 mM diethylamine aqueous solution Mobile phase solution 22: 5 mM 2-methoxyethylamine aqueous solution Mobile phase solution 23: 10 mM cyclopropylamine aqueous solution

[0066] <LC-MS Analysis (Separation Step, Analysis Step)> In Experimental Example 2, the prepared mobile phase solutions 21, 22, and 23 were used as mobile phase C. Next, 100 μM of glucosamine was injected, and LC-MS analysis was performed. The LC analysis was performed under the same conditions as in Experimental Example 1, except that mobile phase C was used instead of mobile phase A. The MS analysis was performed under the same conditions as in Experimental Example 1.

[0067] FIG. 2 is a graph showing peak areas obtained when LC-MS analysis was performed using each mobile phase solution. The vertical axis represents the peak area value for glucosamine. From the results in FIG. 2, in the analysis using mobile phase solution 21 (Comparative Example), almost no peaks derived from glucosamine were detected. Diethylamine contained in mobile phase solution 21 has a high proton affinity and ionizes preferentially over glucosamine in positive mode, which is thought to have reduced detection sensitivity. On the other hand, when mobile phase solutions 22 and 23 (Example) were used, peaks derived from glucosamine were detected. This peak was particularly pronounced when mobile phase solution 23 was used. 2-Methoxyethylamine contained in mobile phase solution 22 and cyclopropylamine contained in mobile phase solution 23 do not ionize preferentially over glucosamine in positive mode, which is thought to have improved detection sensitivity compared to the Comparative Example.

[0068] Aspects It will be understood by those skilled in the art that the exemplary embodiments and examples described above are examples of the following aspects.

[0069] (Item 1) A pH adjuster according to one aspect is a pH adjuster for a mobile phase solvent in a liquid chromatography-tandem mass spectrometer, and contains a primary amine. The pH adjuster described in item 1 provides excellent sensitivity for the analyzer and can adjust the mobile phase to a basic pH.

[0070] (Item 2) In the pH adjuster described in item 1, the primary amine includes a compound having an acid dissociation constant of 8.5 or more, a proton affinity of 930 kJ / mol or less, and a boiling point of 45° C. or more and 200° C. or less. The pH adjuster described in item 2 makes it possible to provide a pH adjuster that has even better detection sensitivity in the analyzer.

[0071] (Item 3) In the pH adjuster according to item 1 or 2, the primary amine comprises at least one compound selected from the group consisting of alicyclic amines and alkoxyalkylamines. The pH adjuster according to item 3 can provide a pH adjuster with even better detection sensitivity in the analyzer.

[0072] (Item 4) In the pH adjuster according to any one of Items 1 to 3, the mobile phase solvent contains at least one selected from the group consisting of water, methanol, acetonitrile, ethanol, 2-propanol, acetone, and tetrahydrofuran. By using the pH adjuster according to Item 4 as the mobile phase solvent, the detection sensitivity of the analyzer can be further improved.

[0073] (Item 5) A mobile phase solution for a liquid chromatograph-tandem mass spectrometer according to one embodiment comprises the pH adjuster and a solvent according to any one of items 1 to 4. The mobile phase solution according to item 5 makes it possible to provide a mobile phase solution that provides excellent detection sensitivity for the analyzer in analysis using a basic mobile phase.

[0074] (Item 6) In the mobile phase solution described in Item 5, the concentration of the primary amine is 1 mM or more and 100 mM or less in the mobile phase solution. The mobile phase solution described in Item 6 makes it possible to provide a mobile phase solution that provides even better detection sensitivity for an analytical device in an analysis using a basic mobile phase.

[0075] (Item 7) A liquid chromatography-mass spectrometry kit according to one embodiment includes the pH adjuster according to any one of Items 1 to 4 and a solvent. The liquid chromatography-mass spectrometry kit according to Item 7 makes it possible to provide a kit that has excellent sensitivity for the analyzer and is capable of adjusting the mobile phase to a basic state.

[0076] (Item 8) The liquid chromatography-mass spectrometry kit according to item 7 further comprises a stationary phase carrier, and the applicable pH range of the stationary phase carrier is from 1 to 14. According to the liquid chromatography-mass spectrometry kit according to item 8, it is possible to provide a kit that not only has excellent detection sensitivity of the analyzer but also excellent resolution in liquid chromatography.

[0077] (Item 9) A method for analyzing an analytical sample according to one aspect includes a preparation step of preparing the analytical sample, a separation step of separating the analytical sample into components using a liquid chromatograph, and an analysis step of analyzing the separated components using a mass spectrometer, wherein a mobile phase for the liquid chromatograph in the separation step contains the pH adjuster described in any one of items 1 to 4. The analytical method described in item 9 enables analysis with excellent detection sensitivity in an analysis using a basic mobile phase.

[0078] (Item 10) In the analytical method according to item 9, the analytical sample contains a basic compound, and the analysis step is performed in a positive mode. According to the analytical method according to item 10, analysis with even better detection sensitivity can be achieved in an analysis using a basic mobile phase.

[0079] (Item 11) In the analytical method according to item 9, the analytical sample contains an acidic compound or a monosaccharide, and the analysis step is performed in a negative mode. According to the analytical method according to item 11, analysis with even better detection sensitivity can be achieved in an analysis using a basic mobile phase.

[0080] Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0081] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include any modifications within the scope of the claims and meanings equivalent to the claims.

Claims

1. A pH adjuster for a mobile phase solvent in a liquid chromatograph-tandem mass spectrometer, the pH adjuster comprising a primary amine.

2. The pH adjuster according to claim 1, wherein the primary amine comprises a compound having an acid dissociation constant of 8.5 or more, a proton affinity of 930 kJ / mol or less, and a boiling point of 45°C or more and 200°C or less.

3. The pH adjuster according to claim 1 or 2, wherein the primary amine comprises at least one compound selected from the group consisting of alicyclic amines and alkoxyalkylamines.

4. The pH adjuster according to claim 1 or 2, wherein the mobile phase solvent comprises at least one selected from the group consisting of water, methanol, acetonitrile, ethanol, 2-propanol, acetone, and tetrahydrofuran.

5. A mobile phase solution in a liquid chromatograph-tandem mass spectrometer, comprising the pH adjuster according to claim 1 or 2 and a solvent.

6. The mobile phase solution according to claim 5, wherein the concentration of the primary amine is 1 mM or more and 100 mM or less in the mobile phase solution.

7. A liquid chromatography-mass spectrometry kit comprising the pH adjuster according to claim 1 or 2 and a solvent.

8. The liquid chromatography-mass spectrometry kit according to claim 7, further comprising a stationary phase carrier, the pH range of the stationary phase carrier being 1 or more and 14 or less.

9. A method for analyzing an analytical sample, comprising: a preparation step of preparing the analytical sample; a separation step of separating the analytical sample into components using a liquid chromatograph; and an analysis step of analyzing the separated components with a mass spectrometer, wherein the mobile phase of the liquid chromatograph in the separation step comprises a pH adjuster as described in claim 1 or claim 2.

10. The analytical method according to claim 9, wherein the analytical sample contains a basic compound, and the analysis step is performed in a positive mode.

11. The analytical method according to claim 9, wherein the analytical sample contains an acidic compound or a monosaccharide, and the analysis step is performed in a negative mode.

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