JP2006053131A - Cationization agent for esi, and sec/esims measuring method using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationization agent hardly generating a higher multiply charged ion even in a high molecular weight of component, and capable of exhibiting an effect of ionizing a slightly ionized material even in a small use amount, as to an ESI method, and an SEC/ESIMS measuring method and SEC/ESIMS measuring instrument using the cationization agent. <P>SOLUTION: This cationization agent for the ESI is a mixture solution of one kind selected from a group comprising a mixture of a potassium halide and KOH, a potassium halide, NaOH, KOH, RbOH and CsOH, and of water. In this SEC/ESIMS measuring method and SEC/ESIMS measuring instrument, a measuring sample is made to flow through an SEC column to conduct SEC separation, the sample after eluted from the column is mixed with the cationization agent, and the sample is ionized by the ESI method to mass-analyze the ionized sample. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cationizing agent used for ionizing a hardly ionized substance such as a synthetic polymer compound in an ESI method (electrospray ionization method). The present invention further relates to a SEC / ESIMS measurement method characterized by using this cationizing agent for ionization by the ESI method, and a SEC / ESIMS measurement apparatus for carrying out the SEC / ESIMS measurement method.

  The MS method (mass spectrometry) is a method in which ions in a gaseous state are separated and detected based on the mass (m) and charge (z) ratio (m / z) of the ions. Information on the structure and molecular weight distribution of polymers can be obtained. In addition, the coupling between the MS method and the GPC method (gel permeation chromatography) is an excellent analysis that makes it possible to obtain more detailed information on the structure and molecular weight distribution of polymer compounds, which is difficult to achieve with the MS method alone. It attracts attention as a method (Analytical Chemistry, Vol. 71, No. 21, November 1, 1999; Non-Patent Document 1).

  In the MS method, the measurement sample needs to be gaseous ions, and an ESI method (electrospray ionization method) is exemplified as the ionization method. This method utilizes the fact that the sample molecules become charged gas ions in the process of drying the charged fine droplets generated by the electrospray phenomenon after dissolving the sample in a polar solvent such as water or methanol. Specifically, an electrospray phenomenon is caused by feeding a sample solution from a thin tube (inner diameter: 0.1 mm) to which a high voltage (-5 KV) is applied, and the sample is ionized.

  When the sample solution is delivered at a high flow rate, the electrospray phenomenon is unlikely to occur. Therefore, even in such a case, an electrospray phenomenon may occur and spraying with an auxiliary gas such as nitrogen gas or air may be used to ionize the sample (ion spray method). The ESI method in the present invention includes a case where spraying with this auxiliary gas is used.

  On the other hand, in the ESI method, a compound having low polarity is not easily ionized. Therefore, as a method for ionizing such a hardly ionized substance (low polarity substance) by the ESI method, a method of performing an electrospray by dissolving an appropriate amount of an alkali metal salt such as NaI in a sample solution is known (non-patent document Reference 1). This NaI or the like is called a cationizing agent.

  By adding NaI or the like, a synthetic polymer compound such as PMMA which is a hardly ionized substance is also ionized by the ESI method. As a result, analysis by the GPC / ESIMS method, which is a method combining the MS method and the GPC method as described above, has become possible. NaI is widely used as a cationizing agent because it is soluble in THF (tetrahydrofuran) which is a mobile phase of GPC.

  Analytical Chemistry, Vol. 71, No. 21, November 1, 1999 (Non-Patent Document 1) shows the results of measuring PMMA by GPC / ESIMS method using NaI as a cationizing agent (FIGURE 2). ). However, this method has a problem that higher molecular weight components tend to generate higher-order multivalent ions, resulting in a complicated spectrum. The higher-order multivalent ions are ions (molecules) having a large number of ions such as Na added to one molecule.

  When the spectrum becomes complicated, analysis such as estimation of molecular weight becomes difficult. Therefore, in the ESI method, a cationizing agent that hardly generates higher-order multivalent ions is desired for high molecular weight components.

In addition, when a large amount of a non-volatile compound such as NaI is continuously introduced into the ion source of a mass spectrometer that performs mass spectrometry, a problem has been found that the introduction pores to the mass analysis part are likely to be blocked. Yes. When the introduction pore is blocked, the sensitivity is lowered, and further, the measurement may be disabled. Therefore, it is desired that the cationizing agent which is a non-volatile compound is as little as possible, and the effect of ionizing a hardly-ionizable substance is sufficient even if the amount used is equal to or less than that of a conventional cationizing agent such as NaI. There has been a desire for a cationizing agent to be exerted.
Analytical Chemistry, Vol.71, No.21, November 1, 1999

  The present invention is a cationizing agent used in the ESI method to ionize hardly ionized substances such as synthetic polymer compounds, and high molecular weight components are less likely to produce higher-order polyvalent ions and are used in a small amount. It is an object to provide a cationizing agent that can sufficiently exhibit the effect of ionizing a hardly-ionized substance even if the amount is small (as a result, it is difficult to cause problems such as blocking of pores introduced into the mass spectrometric part). To do. The present invention is also a SEC (Size Exclusion Chromatography) / ESIMS measurement method using this cationizing agent, the spectrum is not complicated, and analysis of molecular weight estimation up to high molecular weight components is easy, and It is an object of the present invention to provide a durable SEC / ESIMS measurement method that is less likely to cause problems such as blockage of pores introduced into the mass spectrometer.

  As a result of intensive studies on various cationizing agents used for ionization by the ESI method of hardly ionized substances such as synthetic polymer compounds, the present inventor has found that the above-mentioned problem can be solved by using a specific aqueous solution of the compound as the cationizing agent. Was achieved and the present invention was completed.

That is, the present invention is a mixed solution of water and one kind selected from the group consisting of a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH. A cationizing agent is provided (Claim 1). By including water in the cationizing agent, ionization occurs stably, and the reproducibility, sensitivity, and quantitativeness of the spectrum for each scan are improved.
The present invention also provides a cationizing agent for ESI having the following constitution as a more preferred embodiment.

The cationizing agent for ESI, wherein the solution is at least one compound selected from KCl and KOH, or a mixed solution of NaOH and water (Claim 2). Among the above-mentioned cationizing agents for ESI, when a mixed solution of NaOH and water, or a mixed solution of KCl and / or KOH and water is used, higher-order multivalent ions are less likely to be generated, and further better. Spectrum is obtained. In particular, when a cationizing agent for ESI in a mixed solution of NaOH or KOH and water is used, O ₂ generated from the anion portion during cationization tends to have a small background spectrum and a good spectrum tends to be obtained. Furthermore, it is preferable because it tends to reduce the corrosion of the mass spectrometric instrument than the halogen molecules generated from the anion portion in the cationization of potassium halide.

The cationizing agent for ESI, wherein the cationizing agent further comprises an organic solvent mixed with water at an arbitrary ratio (Claim 3).
As a solvent in a mixed solution of a mixture of potassium halide and KOH, one selected from the group consisting of potassium halide, NaOH, KOH, RbOH, and CsOH and water, in addition to water, water and an arbitrary ratio A mixed solvent of an organic solvent mixed with water and water is preferable.

  Here, as an organic solvent mixed with water at an arbitrary ratio, THF, acetonitrile, methanol, ethanol, isopropyl alcohol, 2-methoxyethanol, acetone, dioxane and the like are exemplified. Of these, THF, acetonitrile, and methanol are preferable because they have little interference with the MS spectrum. You may use the mixed solvent which mixed 2 or more types of these solvents, and water.

The cationizing agent for ESI, wherein the cationizing agent contains 10% by weight or more of water (Claim 4).
The amount of water contained in a mixed solution of one selected from the group consisting of a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH and water is preferably 10% by weight or more. . By setting it to 10% by weight or more, potassium halide, NaOH, KOH, RbOH, CsOH can be completely dissolved, and the water concentration in the mobile phase after addition of the cationizing agent should be in a preferred range. Can do.

  The water concentration in the mobile phase after the addition of the cationizing agent is preferably in a range in which the cationizing agent is sufficiently dissolved and the aqueous phase and the phase in which the sample is dissolved are not separated, usually about 2 to 20% by weight. The range of is preferable. By setting it to 2% by weight or more, ionization occurs stably, and the effect of improving the reproducibility, sensitivity, and quantification of the spectrum for each scan is further increased. Further, the content of 20% by weight or less is preferable because the phase separation between the aqueous phase and the polymer solution is more sufficiently suppressed even when the sample is a polymer and the polarity is low.

In the ESI cationizing agent, the total concentration of potassium halide and KOH, NaOH concentration, RbOH concentration, or CsOH concentration is 0.1 to 100 mM / l. Cationizing agent (Claim 5).
In the cationizing agent for ESI, by setting the total concentration of potassium halide and KOH, the concentration of NaOH, the concentration of RbOH, or the concentration of CsOH in the range of 0.1 to 100 mM / l, This is preferable because the concentration of potassium halide, KOH, NaOH, RbOH, and CsOH can be easily controlled.

  The present invention further provides a SEC / ESIMS measurement method characterized by using the ESI cationizing agent. That is, SEC separation was performed by passing a measurement sample through a column, and after adding the cationizing agent for ESI to the mobile phase containing the sample after elution from the column, the sample was ionized and ionized by the ESI method. A SEC / ESIMS measurement method characterized by performing mass spectrometry of a sample (claim 6).

  SEC is a chromatography in which a sample is sieved according to molecular size, and GPC is exemplified as a typical example. Claim 7 corresponds to this aspect, and is the SEC / ESIMS measurement method described above, wherein the SEC separation is GPC separation. That is, the SEC / ESIMS measurement method, that is, the GPC / ESIMS measurement method is provided. It is to provide.

  In the measurement method of claim 6 or claim 7, first, the measurement sample is injected into the SEC apparatus (chromatograph), dissolved in the mobile phase of SEC, and passed through the SEC column as a mobile phase solution. In the case of GPC, THF or the like is used as the mobile phase. As the SEC column and other measurement conditions, the same conditions as those for normal SEC measurement can be employed. The sample passed through the SEC column is SEC-separated in the same manner as in a normal SEC measurement, and the high molecular weight side is first eluted from the column as a mobile phase solution, and the low molecular weight side is eluted over time. All or a part of the eluted sample is ionized by the ESI method and subjected to mass spectrometry. Mass spectrometric analysis of the SEC-separated sample as described above makes it possible to obtain more detailed and accurate information on the molecular weight and its distribution.

  Before mass analysis, the sample is ionized by the ESI method. In the present invention, as a cationizing agent for the ionization, a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH are used. A mixed solution of one kind selected from the group consisting of water and water (cationizing agent for ESI of the present invention) is used. After the mobile phase in which the sample is dissolved is eluted from the SEC column and before being injected into the ESI apparatus for performing the ESI method, the cationizing agent for ESI of the present invention is added to the mobile phase and mixed. (Post column addition method). Or the mobile phase which melt | dissolved the sample in the ESI apparatus, and the cationizing agent for ESI of this invention may be inject | poured simultaneously, and both may be mixed in an ESI apparatus. For example, a device having a triple pipe structure as described in FIG. 1 of Non-Patent Document 1 is used, the eluent from the column is used as the innermost tube, and the solution (cationizing agent) is used as the middle tube. ), An auxiliary gas is allowed to flow through the outermost pipe and sprayed directly into the ESI apparatus. According to this method, the cationizing agent for ESI of the present invention, that is, one kind selected from the group consisting of a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH, and water Samples that are difficult to dissolve in the mixed solution are also preferable because analysis becomes easy.

  In order to minimize contamination of the ion source of the mass spectrometer with potassium halide, NaOH, KOH, RbOH, and CsOH, the mixing of the cationizing agent for ESI of the present invention and the mobile phase is performed in the mobile phase. It is preferred that it be performed only when the sample is included. Since the time when the sample is contained in the mobile phase is limited to one time after a certain time has elapsed after the sample is injected into the SEC column, it is preferable to mix the solution only at this time.

  The total concentration of potassium halide and KOH, the concentration of NaOH, the concentration of RbOH, or the concentration of CsOH in the mobile phase is preferably in the range of 1 μM / l to 10 mM / l. When the concentration is 1 μM / l or more, the ionization effect of the hardly ionic high molecular weight component is excellent, and when the concentration is 10 mM / l or less, blocking of the introduction pore of the mass spectrometer is suppressed. In particular, in the range of 10 μM / l to 1 mM / l, these effects are remarkable and more preferable. Further, the flow rate of the mobile phase injected into the ESI apparatus is preferably in the range of 0.1 to 2.0 ml / min. Within this range, data with high sensitivity and good S / N can be obtained. Particularly in the range of 0.1 to 0.8 ml / min, these effects are remarkable and more preferable. Claim 8 corresponds to this preferred embodiment, and is the SEC / ESIMS measurement method described above, wherein the cationizing agent for ESI of the present invention, that is, a mixture of potassium halide and KOH, potassium halide, NaOH. , KOH, RbOH, and one selected from the group consisting of CsOH and a mixed phase of water and a mobile phase after addition of water, the total concentration of potassium halide and KOH, the concentration of NaOH, the concentration of RbOH, or SEC / ESIMS measurement characterized in that the concentration of CsOH is 1 μM / l to 10 mM / l and the flow rate of the mobile phase containing the sample subjected to the ESI method is 0.1 to 2.0 ml / min. A method is provided.

  The SEC / ESIMS measurement method of the present invention can be applied to a compound that can perform SEC analysis and contains S and / or O in the molecule, and can also analyze a compound having a molecular weight of less than 3000. Conventionally difficult to ionize, analysis of poorly ionized substances having molecular weight of about 3000 to 20,000 containing S and / or O in the molecule, especially synthetic polymer compounds having 10 to 160 structural units derived from monomers It is preferably applied to. Examples of such synthetic polymer compounds include polyester, polyether, polysulfide, polysulfone, polyetherketone, polyamide, epoxy resin, phenol resin, silicon resin, acrylic resin, polyethylene glycol, polypropylene glycol, polyacrylic acid, polyvinyl alcohol, etc. Is mentioned.

  Examples of the mobile phase used in the SEC / ESIMS measurement method of the present invention include hydrocarbons such as hexane, heptane and chloroform, ethers such as tetrahydrofuran, nitriles such as acetonitrile, alcohols such as methanol, ethanol and propanol. And esters such as ethyl acetate (claim 9). Conventionally, acetonitriles and alcohols that have been used in mobile phases as a mixed solvent with water can also be applied to the measurement using the cationizing agent of the present invention. It has been found that mobile phases that are not sufficiently mixed with water, such as hydrogen, ethers, and esters, can be applied because they are mixed with the cationizing agent immediately before cationization.

  The present invention further provides an SEC / ESIMS measurement apparatus for performing the SEC / ESIMS measurement method of the present invention. That is, a SEC separation device for performing SEC separation of a measurement sample, a storage tank for the cationizing agent for ESI, and a cationizing agent feed for feeding the cationizing agent in the storage tank for mixing with the sample eluted from the SEC separation device. A SEC / ESIMS measuring apparatus comprising a liquid means, an ESI apparatus that ionizes a sample mixed with the solution, and a mass spectrometer that performs mass analysis of the ionized sample (claim 10).

  Here, the SEC separation device is a means for collecting a sample, for example, an autosampler, a storage tank for a mobile phase such as THF, a pump for feeding the mobile phase to a column, a sample dissolved in the mobile phase with a molecular size. It has a column for sieving according to the thickness. Further, when a detector such as a UV detector or an RI detector is provided, SEC can be measured simultaneously.

  The cationizing agent feeding means is a feeding pump or the like, and is selected from the group consisting of a cationizing agent in a storage tank, that is, a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH. This is a solution for feeding a mixed solution of one kind of water and water and mixing it with a mobile phase containing a sample eluted from the SEC separator. As a method of mixing, a method of mixing by adding to the mobile phase after elution from the column and before injection into the ESI device, a method of spraying the sample in the ESI device together with the sample using the above triple tube, etc. Is mentioned.

  The sample required for mass spectrometry is usually smaller than the sample eluted from the SEC column. Therefore, a branching section may be provided in the middle of the pipe connecting the elution port of the SEC column and the sample injection port to the ESI apparatus so that only a part of the eluted sample is subjected to mass spectrometry.

  As described above, only when the sample is eluted from the SEC column, a cationizing agent, that is, one kind selected from the group consisting of a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH. Further, by adding and mixing a mixed solution with water, contamination of the ion source of the mass spectrometer can be minimized. Therefore, it is preferable that the cationizing agent feeding means operates based on the collection of the sample by the SEC separation device. In other words, the time when the sample elutes from the SEC column is limited to a certain time after a certain time has elapsed since the sample was collected by the autosampler or the like, so that the cationizing agent feeding means operates only during this certain time. In order for the solution to be delivered, the cationizing agent delivery means and the autosampler, etc. are interlocked, for example, so that the delivery starts after a certain time of collection, and the delivery ends after the certain time. It is preferable that Claim 11 corresponds to this preferred mode.

  The ESI method using the ESI cationizing agent of the present invention, that is, a mixed solution of water selected from the group consisting of a mixture of potassium halide and KOH, one selected from the group consisting of potassium halide, NaOH, KOH, RbOH, and CsOH When it is carried out, high-order multivalent ions are hardly generated even for high molecular weight components such as synthetic polymer compounds. On the other hand, even if the amount used is small, the effect of ionizing a hardly ionized substance such as a synthetic polymer compound is sufficiently exhibited. Therefore, when SEC / ESIMS measurement is performed using this cationizing agent for ESI, high-order multivalent ions are not easily generated, so the spectrum does not become complicated, and analysis such as estimation of molecular weight up to high molecular weight components is easy. To. In addition, since the amount used can be reduced, it is difficult for the pores introduced into the mass spectrometer to be blocked. That is, the SEC / ESIMS measurement method of the present invention has the effect that the spectrum is not complicated and the introduction pores into the mass spectrometer are less likely to be clogged. It is suitably used for analyzing the molecular structure and molecular weight distribution of substances.

  Next, the best mode for carrying out the present invention will be described. In addition, this invention is not limited to this form, The change to another form is also possible unless the meaning of this invention is impaired.

  FIG. 1 is a flowchart showing a flow of an example of the SEC / ESIMS measurement method of the present invention. The SEC method performed in the example of FIG. 1 is the GPC method. The part where the GPC method is carried out is a storage tank for THF as a mobile phase, a GPC pump section for feeding THF from this storage tank to an autosampler section and a GPC column, an autosampler section for automatically injecting a measurement sample, GPC It consists of a column part that performs separation and a detector that detects a sample in the mobile phase eluted from the column.

  A measurement sample, for example, a solution of a synthetic polymer such as PMMA is injected from the autosampler part and dissolved in THF as a mobile phase. When the sample is manually injected, the autosampler portion may not be provided. Since the optimal amount of sample injection varies depending on the molecular weight and molecular weight distribution of the sample to be measured, the range cannot be limited. However, the sample concentration is generally in the range of about 1 mg / ml to 100 mg / ml. The volume is 100 μl or less.

  The THF in which the measurement sample is dissolved is passed from the autosampler part to the column part, and GPC separation is performed. A column thermostat for maintaining the column at a constant temperature may be used, and when performing high-temperature GPC, a dedicated thermostat may be used. The GPC column used is not particularly limited as long as it is a hydrophobic column that can flow at a flow rate of 0.1 ml / min or more. In the case of the SEC method other than the GPC method, the column may not be hydrophobic. The number of columns is also appropriately selected according to the purpose of measurement.

  In the example of FIG. 1, the THF solution containing the sample separated by GPC in the column portion is passed through the detector, the change in the amount of the sample eluted with respect to the elution time is measured, and a GPC chromatogram is obtained. Examples of the detector include a UV detector (UV-VIS detector) and an RI detector, and either or both of them are used. In the example of FIG. 1, both a UV detector and an RI detector are used. An RI detector is used to obtain information about the molecular weight distribution. In order to carry out the SEC / ESIMS measurement method of the present invention, it is not always necessary to obtain a GPC chromatogram, and therefore a detector may not be used.

  In the example shown in FIG. 1A, a KCl aqueous solution (cationizing agent) is added to and mixed with a THF solution containing a sample flowing out from the detector, and then supplied to the ESI apparatus. In this example, a KCl aqueous solution is used, but a KOH aqueous solution or the like may be used instead. As shown in FIG. 1A, in this example, the flow of the THF solution containing the sample is branched before the addition of the KCl aqueous solution, and the KCl aqueous solution is added to only a part of this flow. For example, the flow of the THF solution containing the sample flowing out from the detector (usually about 0.1 to 2.0 ml / min) is branched, and the KSI aqueous solution is added only to the flow of about 0.01 ml / min, and the ESI apparatus May be supplied. Further, this branching may be performed after adding the KCl aqueous solution. However, when it is performed after adding the KCl aqueous solution, a large amount of the KCl aqueous solution is required.

  In the example shown in FIG. 1 (b), the THF solution containing the sample eluted from the column was branched, and KCl aqueous solution (cationizing agent) was added to only one, mixed, and then supplied to the ESI apparatus and branched. The remainder is passed through a UV detector and an RI detector. For example, the KCl aqueous solution may be added to only about 0.01 ml / min in the flow about 0.1 to 2.0 ml / min eluted from the column and supplied to the ESI apparatus.

  In the example of FIG. 1, the injection part for injecting the KCl aqueous solution (cationizing agent) is provided before injecting the sample solution into the ESI apparatus. The injection part is usually constituted by a tea branch or the like, and can freely inject and stop the injection of the cationizing agent according to the elution time or the like. Instead of using such an injection part, a KCl aqueous solution may be injected into the ESI apparatus together with the sample solution and the auxiliary gas using a triple tube or the like.

  A cationizing agent such as a KCl aqueous solution is stored in a cationizing agent storage tank (KCl aqueous solution storage tank or the like), and is sent to the injection section by a cationizing agent addition pump (cationizing agent feeding means). In the example of the apparatus shown in FIG. 1, three cationizing agent storage tanks are provided, and three kinds of cationizing agents can be set in advance, and any of the three kinds of cationizing agents can be set at any time at any time. It is designed to deliver liquid. Therefore, since the type to be added can be easily changed up to three types, it is possible to automatically examine the type of cationizing agent. By creating a program in advance for the measurement conditions, it is possible to perform unattended measurement. For example, as three kinds of cationizing agents, it is also easy to compare the effect of the present invention with a comparative example using KCl aqueous solution or KOH aqueous solution and other cationizing agents not corresponding to the present invention. Further, the comparison of the solvents and the influence of the concentration can be easily measured by the combination of the various kinds of the KCl aqueous solution or the KOH aqueous solution and the KCl or KOH concentration.

  As the pump for adding a cationizing agent, a pump capable of arbitrarily changing the liquid feeding amount is preferably used. Using such a pump, it is also possible to increase the addition rate during the measurement by setting the addition rate to 0 ml / min at the beginning of the measurement.

  In the example of FIG. 1, the pump for adding a cationizing agent is controlled based on a signal from an autosampler unit. That is, the control of the cationizing agent feeding is programmed in advance, the program is started in synchronization with the start signal (trigger) from the autosampler, and the timing of addition and the amount of feeding are controlled.

  The analysis by GPC usually requires several tens of minutes or more, but the time for detecting the sample is about half that time, and the cationizing agent is required only in the elution section of the sample. By controlling the addition time and amount of the cationizing agent as described above, it is possible to extend the durability time (time until clogging) of mass spectrometry measurement, which is preferable. Therefore, as an apparatus used in the measurement method of the present invention, an apparatus that can arbitrarily control the addition time and amount of the cationizing agent is preferable. In addition, the method of controlling the liquid feeding is not limited to the above method, and a method using a separate computer is also possible.

  The sample solution mixed with the KCl aqueous solution (cationizing agent) is injected into the ESI apparatus and ionized. Alternatively, the sample and the KCl aqueous solution may be simultaneously injected into the ESI apparatus by a triple tube or the like. The ESI apparatus for performing the ESI method and the ESI conditions are the same as those of the conventional ESI method using an auxiliary gas or a cationizing agent, except for the above conditions such as the type of cationizing agent and the type of solvent. And conditions can be adopted.

  A sample ionized and vaporized by the ESI method is subjected to an MS method (mass spectrometry) by a mass spectrometer. As the MS method, FTMS or the like that can achieve high resolution can be preferably used. In this way, more detailed measurement results on the molecular structure and molecular weight distribution of the measurement sample can be obtained.

  Next, examples and comparative examples of the present invention are shown. The scope of the invention is not limited by the examples.

Example 1 and Comparative Example 1
[Measurement sample]
The following 5 types of THF solutions of standard PMMA for GPC manufactured by Polymer Laboratories were obtained. (1) :( 2) :( 3) :( 4) :( 5) = 1: 2: 1: 1: 1 Samples prepared by mixing at a ratio (volume ratio) (1) A solution in which 2.2 mg of PMMA3100 was dissolved in 2 ml of THF.
(2) A solution obtained by dissolving 5.91 mg of PMMA 6540 in 12 ml of THF.
(3) A solution obtained by dissolving 4.38 mg of PMMA9400 in 4 ml of THF.
(4) A solution obtained by dissolving 11.57 mg of PMMA12700 in 12 ml of THF.
(5) A solution in which 2.45 mg of PMMA 29300 is dissolved in 2.4 ml of THF.

[Cationizing agent]
Preparation Method of Cationizing Agent (KCl Aqueous Solution) 100 ml of ion exchange water and 100 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. A reagent special grade KCl manufactured by Wako Pure Chemical Industries, Ltd. is dissolved in ion exchange water and adjusted to 100 mM / l. This solution is weighed with 2 ml Eppendorf and added to the mixed solvent. The obtained solution having a KCl concentration of 1 mM / l was used as a cationizing agent.

Preparation Method of Cationizing Agent (KOH Aqueous Solution) 100 ml of ion exchange water and 100 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. A reagent special grade KOH manufactured by Wako Pure Chemical Industries, Ltd. is dissolved in ion exchange water and adjusted to 100 mM / l. This solution is weighed with 2 ml Eppendorf and added to the mixed solvent. The obtained solution having a KOH concentration of 1 mM / l was used as a cationizing agent.

Preparation method of cationizing agent (KI aqueous solution) A reagent special grade KI made by Hayashi Junyaku was dissolved in ion-exchanged water and adjusted to 100 mM / l. This solution is weighed with 1 ml Eppendorf and added to 100 ml of methanol (MTA). The obtained solution having a KI concentration of 1 mM / l was used as a cationizing agent.

Preparation Method of Cationizing Agent (NaI Aqueous Solution) Reagent special grade NaI made by Hayashi Junyaku was dissolved in ion-exchanged water and adjusted to 100 mM / l. This solution is weighed with 1 ml Eppendorf and added to 100 ml of methanol (MTA). The obtained NaI concentration was 1 mM / l as a cationizing agent.

  About the sample obtained above, GPC / ESIMS measurement was performed using each said cationizing agent (KOH aqueous solution or KI aqueous solution) (Example 1). In order to show the effectiveness of the present invention, GPC / ESIMS measurement was performed under the same conditions using the cationizing agent (NaI aqueous solution) (Comparative Example 1).

[GPC measurement conditions]
Apparatus: Agilent 1100 Series LC
Column: TSKgelSuperHZ (4000 × 3 + 3000 + 2500 × 2)
6.0mmφ × 150mm
Mobile phase: THF
Flow rate: 0.25 ml / min Sample injection volume: 25.0 μl

[ESIMS measurement conditions]
Apparatus: HP / LCD / MSD
Ionization method: ESI +
Scan range (m / z): 300 to 3000
Scan time: about 5 seconds Scan mode: Full
Vcap voltage: 5000V
Fragmentor (V): 400
Dry gas: 100 ° C., 13.0 l / min Atomizing gas pressure: 30 psi
Post column addition rate of cationizing agent: 0.05 ml / min

[Measurement result]
The GPC / ESIMS measurement was performed by putting each of the three cationizing agents in each cationizing agent storage tank based on the flow of FIG. Further, the entire amount (0.25 ml / min) of the sample eluted from GPC was subjected to mass spectrometry (ESIMS method).

  The GPC method was performed once for each cationizing agent, for a total of 4 times. FIG. 2 shows a GPC chromatogram with a 220 nm UV detector in each case (the horizontal axis is the elution time (minutes)). The four chromatograms agree very well and the GPC measurement reproducibility is good. Therefore, it may be determined that the same component is eluted during the same elution time.

  FIG. 3 shows an integrated average spectrum for an elution time of 58 minutes to 60 minutes. Despite the elution of the same component, there is a difference in the spectrum for each measurement with a different cationizing agent. The spectrum of NaI aqueous solution addition (FIG. 3 (a)) has a large peak on the smaller m / z side, while the spectrum of KCl aqueous solution addition (FIG. 3 (c)) and the spectrum of KOH aqueous solution addition (FIG. 3 (d)). ) Has a large peak on the larger m / z side, and the spectrum of the addition of the KI aqueous solution (FIG. 3B) is in the middle. Since m (molecular weight) is considered to be almost the same for all four times, a large peak is obtained when the NaI aqueous solution is added and the z (valence) is large, while z (( It is clear that a large peak is obtained when the valence is small. That is, the results of FIG. 3 show that higher-order ions (multivalent ions) are most easily generated when an aqueous NaI solution is added, while higher-order ions (multivalent ions) are added when an aqueous KCl solution or an aqueous KOH solution is added. Indicates that it is the most difficult to generate. Further, the spectrum of the NaI aqueous solution addition (FIG. 3A) is more complex than the spectrum of the KCl aqueous solution or KOH aqueous solution addition (FIGS. 3C and 3D) and is difficult to analyze. It is shown.

  In order to numerically compare the ease of generation of higher-order ions, based on the GPC / ESIMS measurement results, the molecular size (n number) of PMMA and the detection intensity of multivalent ions (area of MS chromatogram) FIG. 4 is a graph showing this relationship.

  As is clear from FIG. 4, the divalent ion (FIG. 4 (a)) when the NaI aqueous solution was added was detected with the maximum intensity of molecules having about 25 units of MMA, whereas 33 units when the KCl aqueous solution was added. When the KOH aqueous solution is added, the maximum is about 35 units. That is, when NaI aqueous solution is added, divalent ions are added at a rate of 1 to 12-13 units, whereas when KCl aqueous solution is added, it is 1 per 16-17 units, when KOH aqueous solution is added. Means that K + is added at a rate of 1 to 17-18 units.

  As for trivalent ions (FIG. 4 (b)), when NaI aqueous solution is added, the maximum is about 38 units, and one is added to 12-13 units, while when KCl aqueous solution is added, it is maximum at about 59 units. One unit is added to 19 to 20 units, and when KOH aqueous solution is added, the maximum is about 65 units, and one unit is added to 21 to 22 units. From this result, when a molecule having 35 units of MMA is considered, when a NaI aqueous solution is added, trivalent ions are mainly detected, whereas when a KCl aqueous solution or KOH aqueous solution is added, divalent ions are mainly detected. Will be. Therefore, it is clear from the results of Examples and Comparative Examples that higher-order multivalent ions are less likely to be generated in KCl and KOH, and as a result, it is easier to analyze even high molecular weight components. As for KI, intermediate performance between NaI and KCl or KOH is shown.

  FIG. 5 shows the integrated average spectrum of the elution time from 51 minutes to 51.5 minutes (high molecular weight region). When KCl aqueous solution or KOH aqueous solution is added, the peak intensity is large and a spectrum with a clear peak interval is obtained (FIGS. 5 (c) and 5 (d)), but when the NaI aqueous solution is added, the peak intensity is small. (FIG. 5A), various analyzes from this data are difficult. KI shows the intermediate performance (FIG. 5B). That is, when adding an aqueous NaI solution, it is difficult to obtain a clear MS spectrum in the high molecular weight region, but there is no such problem when adding a KCl aqueous solution or an aqueous KOH solution, and measurement is easy even in the high molecular weight region. Results are obtained.

Example 2
GPC / ESIMS measurement was performed under the same conditions as in Example 1 except that the following cationizing agent was used. The total ion chromatography obtained as a result is shown in FIG.

Preparation method of cationizing agent 1 (KCl solution, water: acetonitrile = 5: 95) 4 ml of ion-exchanged water and 95 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. A reagent special grade KCl manufactured by Wako Pure Chemical Industries, Ltd. is dissolved in ion exchange water and adjusted to 100 mM / l. This solution is weighed with 1 ml Eppendorf and added to the mixed solvent. The resulting solution with a KCl concentration of 1 mM / l was designated as cationizing agent 1.

Preparation Method of Cationizing Agent 2 (KCl Solution, Water: Acetonitrile = 50: 50) 49 ml of ion-exchanged water and 50 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. Thereafter, the cationizing agent 2 having a KCl concentration of 1 mM / l was obtained in the same manner as the method for preparing the cationizing agent 1.

Preparation Method of Cationizing Agent 3 (KCl Solution, Water: Acetonitrile = 95: 5) 94 ml of ion exchange water and 5 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. Thereafter, the cationizing agent 3 having a KCl concentration of 1 mM / l was obtained in the same manner as the method for preparing the cationizing agent 1.

  Compared with the case where the cationizing agent 1 having a water content of less than 10% by weight in the solvent is used (FIG. 6 (a)), the cationizing agent having a water content of 10% by weight or more. 2 (FIG. 6 (b)) or the cationizing agent 3 (FIG. 6 (c)), as is clear from FIG. 6, the sensitivity of the total ion chromatography is high and smooth. Yes, with excellent spectral sensitivity, reproducibility, and quantification for each scan.

Example 3 and Comparative Example 2
[Measurement sample]
The following 5 types of THF solutions of standard PMMA for GPC manufactured by Polymer Laboratories were obtained, and (1) :( 2) :( 3) :( 4) :( 5) = 1: 1: 1: 1: 1. (1) A solution in which 1.24 mg of PMMA3100 was dissolved in 1.2 ml of THF.
(2) 1.02 mg of PMMA 6540 dissolved in 1.0 ml of THF.
(3) 1.07 mg of PMMA9400 dissolved in 1.1 ml of THF.
(4) PMMA12700 1.59mg dissolved in 1.6ml THF.
(5) 1.16 mg of PMMA 29300 dissolved in 1.2 ml of THF.

[Cationizing agent]
Preparation Method of Cationizing Agent (NaOH Aqueous Solution) 100 ml of ion exchange water and 100 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. A reagent special grade NaOH manufactured by Wako Pure Chemical Industries, Ltd. is dissolved in ion exchange water and adjusted to 100 mM / l. This solution is weighed with 2 ml Eppendorf and added to the mixed solvent. The obtained solution having a NaOH concentration of 1 mM / l was used as a cationizing agent.

Preparation Method of Cationizing Agent (NaI Aqueous Solution) 100 ml of ion exchange water and 100 ml of acetonitrile (ATN) are mixed to obtain a mixed solvent. A reagent special grade NaI manufactured by Wako Pure Chemical Industries, Ltd. is dissolved in ion-exchanged water and adjusted to 100 mM / l. This solution is weighed with 2 ml Eppendorf and added to the mixed solvent. The obtained NaI concentration was 1 mM / l as a cationizing agent.

About the sample obtained above, GPC / ESIMS measurement was performed on the measurement conditions shown below using each said cationizing agent.
The sample obtained above was subjected to GPC / ESIMS measurement using a cationizing agent (NaOH aqueous solution) (Example 3). In order to show the effectiveness of the present invention, a GPC / ESIMS measurement was performed under the same conditions using a cationizing agent (NaI aqueous solution) (Comparative Example 2).

[GPC measurement conditions]
The same conditions as in Example 1 except that the column was TSKgelSuperHZ 4.6 mmφ × 150 mm (4000 × 4 + 3000 + 2500 × 2).
[ESIMS measurement conditions]
The same conditions as in Example 1 except that the Vcap voltage was 4500 V and the post column addition rate of the cationizing agent was 0.05 ml / min.

[Measurement and measurement results]
In the same manner as in Example 1, the measurement by the GPC method was performed once for each cationizing agent twice in total. FIG. 7 shows an integrated average spectrum for an elution time of 58 minutes to 59 minutes. As in the case of Example 1, although the same component is eluted, a difference is seen in the spectrum in each measurement with different cationizing agents. The spectrum of the NaI aqueous solution addition (FIG. 7 (a)) has a large peak on the side with a small m / z, while the spectrum of the NaOH aqueous solution addition (FIG. 3 (b)) has a large peak on the side with a large m / z. . Since m (molecular weight) is considered to be substantially the same in both measurements, a large peak is obtained when the NaI aqueous solution is added when the z (valence) is large, while the z (valence) is obtained when the NaOH aqueous solution is added. It is clear that a large peak is obtained when is small. That is, the results of FIG. 7 show that high-order ions (multivalent ions) are easily generated when the NaI aqueous solution is added, whereas high-order ions (multivalent ions) are not easily generated when the NaOH aqueous solution is added. It is shown that. Similar to the relationship between NaI and KOH in Example 1, NaI, which easily generates higher-order ions, has a higher molecular weight component spectrum than NaOH, making analysis difficult.

In order to numerically compare the ease of generation of higher-order ions following Example 1, based on the measurement results of GPC / ESIMS, the molecular size (n number) of PMMA and the detection intensity of multivalent ions (MS FIG. 8 is a graph showing the relationship with the area of the chromatogram. As is clear from FIG. 8, the trivalent ions (FIG. 8) when the NaI aqueous solution was added were detected with the maximum intensity of molecules having about MMA 47 units, whereas the trivalent ions were about 56 units when the NaOH aqueous solution was added. When it is the maximum. That is, while the trivalent ions when NaI solution added are added Na ⁺ with one proportion 16-17 units, when added NaOH aqueous solution at a rate of one to 18-19 units, added Na + Will be.

It is a flowchart which shows the flow of GPC / ESIMS measurement of this invention. 2 is a GPC chromatogram obtained in Example 1 and Comparative Example 1. It is the MS spectrum obtained by GPC / ESIMS measurement obtained in Example 1 and Comparative Example 1. It is a graph which shows the relationship between molecular size and the detection intensity | strength of multivalent ion. It is the MS spectrum obtained by GPC / ESIMS measurement obtained in Example 1 and Comparative Example 1. 2 is a total ion chromatogram obtained in Example 2. FIG. It is the MS spectrum obtained by GPC / ESIMS measurement obtained in Example 3 and Comparative Example 2. It is a graph which shows the relationship between the molecular size and the detection intensity | strength of a multivalent ion in Example 3 and Comparative Example 2. FIG.

Claims (11)

  A cationizing agent for ESI, which is a mixed solution of one selected from the group consisting of a mixture of potassium halide and KOH, potassium halide, NaOH, KOH, RbOH, and CsOH, and water.   The cationizing agent for ESI according to claim 1, wherein the solution is at least one compound selected from KCl and KOH, or a mixed solution of NaOH and water.   The cationizing agent for ESI according to claim 1 or 2, wherein the cationizing agent further contains an organic solvent mixed with water at an arbitrary ratio.   The cationizing agent for ESI according to any one of claims 1 to 3, wherein the cationizing agent contains 10% by weight or more of water.   In the cationizing agent, the total concentration of potassium halide and KOH, the concentration of NaOH, the concentration of RbOH, or the concentration of CsOH is 0.1 to 100 mM / l. Item 5. The cationizing agent for ESI according to any one of Items 4.   The measurement sample is passed through the column to perform SEC separation, and after adding the ESI cationizing agent according to any one of claims 1 to 5 to the mobile phase containing the sample eluted from the column, ESI A SEC / ESIMS measurement method comprising ionizing a sample by a method and performing mass spectrometry of the ionized sample.   The SEC / ESIMS measurement method according to claim 6, wherein the SEC separation is GPC separation.   In the mobile phase after adding the ESI cationizing agent, the total concentration of potassium halide and KOH, the concentration of NaOH, the concentration of RbOH, or the concentration of CsOH is 1 μM / l to 10 mM / l, The SEC / ESIMS measurement method according to claim 6 or 7, wherein the flow rate of the mobile phase containing a sample to be subjected to the ESI method is 0.1 to 2.0 ml / min.   9. The mobile phase according to claim 6, wherein the mobile phase is at least one solvent selected from the group consisting of hydrocarbons, ethers, nitriles, alcohols, and esters. SEC / ESIMS measurement method.   A SEC separation device for performing SEC separation of a measurement sample, a storage tank for the cationizing agent for ESI according to any one of claims 1 to 5, and a sample obtained by eluting the cationizing agent in the storage tank from the SEC separation device; SEC / ESIMS measurement comprising: a cationizing agent feeding means for feeding for mixing; an ESI device for ionizing a sample mixed with the solution; and a mass spectrometer for performing mass analysis of the ionized sample apparatus. 11. The SEC / ESIMS measuring apparatus according to claim 10, wherein the cationizing agent liquid feeding means operates based on a sample collection time by the SEC separation apparatus.

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