JP2010025714A - Method of adding ionizing agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional ESI that sensitivity is low. <P>SOLUTION: A liquid sample is sprayed from a needle of an electro-spray device, and an ionizing agent droplet is added before the sample is introduced to a mass spectrograph, thereby improving the sensitivity of mass analysis. Specifically, several μL of an ionizing agent droplet is dropped from a syringe to positions of a proximity of the tip of the needle of the electro-spray device, a proximity of the tip of a cone of the mass spectrograph, and an intermediate part between the needle and the cone, thereby adding the ionizing agent to the sample. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to mass spectrometry of substances, and more particularly to ionization of a sample prior to mass analysis.

  The 2002 Nobel Prize in Chemistry was awarded by Koichi Tanaka for the invention of matrix-assisted laser desorption / ionization (MALDI), which is effective for soft ionization mass spectrometry of macromolecules. Prof. Fenn received the award.

This ESI is an atmospheric pressure ionization method (API;
Atmospheric pressure ionization) is characterized by ionization under atmospheric pressure, and is a very effective method in that the solvent is removed outside the vacuum.

  ESI is the softest ionization method among the currently used ionization methods. Soft means that the sample molecules are made into gaseous ions without being decomposed. Suitable for compounds that have acidic or basic functional groups and ionize in solution.

  As shown in FIG. 1, a high voltage of several thousand volts is applied to the needle tip from which the sample solution flows out, and its role is to positively divide the sample molecules in the solution into positive ions and negative ions. When a positive high voltage is applied to the tip of the needle, a solution containing a large amount of positive ions collects at the tip of the needle. When a nitrogen stream is allowed to act on the solution flowing out at this time, evaporation of the solvent is promoted together with the spraying of fine droplets, and so to speak, stuffed-off ions appear in the gas.

When the high voltage applied to the needle tip is positive, the generated ions are protonated molecules [M + H] ⁺ and polyvalent protonated molecules [M + nH] ^{n +} . When a negative high voltage is applied, a deprotonated molecule [M−H] ⁻ or a polyvalent deprotonated molecule [M−nH] ⁿ⁻ is generated.

  ESI is an effective ionization method for ionic and highly polar compounds (see FIG. 1). The sample solution is guided to a needle having a high voltage of about 3 to 5 kV applied to the tip. By flowing and spraying atomized gas (also called nebulizer gas) from the outside of the needle, fine charged droplets having the same sign as the applied voltage are produced.

However, this ESI has a drawback that the sensitivity is not necessarily high (see Patent Document 1).
JP 2002-190272 A

  The problem of the present invention is to eliminate the low sensitivity that has been a drawback of the conventional ESI.

  In the present invention, a liquid sample is sprayed from the needle of an electrospray apparatus, and the ionization agent droplet is added before the sample is introduced into the mass analyzer, thereby improving the sensitivity of mass spectrometry.

  As shown in FIG. 2, specifically, the vicinity of the tip of the needle of the electrospray apparatus (hereinafter referred to as “needle tip”), the vicinity of the tip of the cone of the mass analyzer (hereinafter referred to as “cone”), and the needle tip The ionizing agent is added to the sample by dropping several μL of the ionizing agent droplet from the syringe at a position intermediate the cone.

  In the present invention, a liquid sample is sprayed from the needle of the electrospray device, and before the sample is introduced into the mass analyzer, the ionizer droplet is added to greatly improve the sensitivity of mass spectrometry. Can do.

The best mode for carrying out the present invention will be described below.
The sample was fed with a syringe pump and electrosprayed. An ionizing agent was added by each method shown in FIG. 2, and IT / MS measurement was performed with a mass spectrometer M-8000 manufactured by Hitachi, Ltd.

As a sample, 1.0 mM linoleic acid methyl ester (MeLin, molecular weight 294.47) was adjusted with methyl alcohol (MeOH). As an ionizing agent, about 2 μL of lithium chloride (LiCl) droplets were dropped by a syringe near the outlet of the needle of the electrospray device (indicated as “needle tip” in FIG. 2). The drops were sprayed and [M + Li] ⁺ ions (m / z 302) were confirmed (see FIG. 3).

As in Example 1, MeLin was used as a sample, and LiCl as an ionizing agent was dropped in the vicinity of the cone inlet of the mass spectrometer (indicated as “cone” in FIG. 2). As a result, [M + Li] ⁺ ion ( m / z 302) was confirmed (see FIG. 4).

For comparison, only MeLin of the sample was electrosprayed and subjected to mass spectrometry, and [M] ⁺ was not detected (see FIG. 5).

  Next, for comparison, when a liquid in which the sample MeLin and the ionizing agent LiCl were mixed was electrosprayed, (m / z 301) was confirmed (see FIG. 6).

As a sample, carbamazepine (Carbamazepine, molecular weight 236.27, pharmaceutical) 1.0 mM was prepared with methyl alcohol (MeOH). As an ionizing agent, about 2 μL of a lithium chloride (LiCl) droplet was dropped by a syringe in the vicinity of the outlet of the needle of the electrospray device (indicated as “needle tip” in FIG. 2), and [2M + Li] ⁺ Ion (m / z 479.41) was confirmed (see FIG. 7).

As in Example 3, carbamazepine was used as a sample, and LiCl as an ionizing agent was dropped in the vicinity of the cone inlet of the mass spectrometer (indicated as “cone” in FIG. 2). As a result, [2M + Li] ⁺ ion ( m / z 479.21) was confirmed (see FIG. 8).

For comparison, when only the sample carbamazepine was electrosprayed and subjected to mass spectrometry, [M] ⁺ was not detected (see FIG. 9).

As a sample, 1.0 mM of ethofenprox (molecular weight 376.49, pesticide) was prepared with methyl alcohol (MeOH). As an ionizing agent, about 2 μL of a lithium chloride (LiCl) droplet was dropped by a syringe in the vicinity of the outlet of the needle of the electrospray device (indicated as “needle tip” in FIG. 2), and [M + Li] ⁺ Ion (m / z 383.35) was confirmed (see FIG. 10).

As in Example 5, etofenprox was used as a sample, and LiCl as an ionizing agent was dropped in the vicinity of the cone inlet of the mass spectrometer (indicated as “cone” in FIG. 2). ] ⁺ ion (m / z 359.35) has been confirmed, [M + ^{Li] +} ion was observed (see FIG. 11).

For comparison, only the sample etofenprox was electrosprayed and mass analyzed, and [M] ⁺ was not detected (see FIG. 12).

  In the above example, the example in which the droplet is dropped near the tip of the needle or near the tip of the cone has been described, but the same effect can be obtained by dropping the droplet at an intermediate position between the needle and the cone.

In the above embodiments, an example in which a droplet is dropped has been described. However, a droplet is simply held at the tip of a syringe and placed near the tip of the needle, at an intermediate position between the needle and the cone, or near the tip of the cone. However, similar results can be obtained.

Illustration of the principle of electrospray Conceptual illustration of droplet addition in the present invention Mass spectrometry result when MeLin is electrosprayed as a sample and LiCl is dropped as an ionizing agent in the vicinity of the needle tip of the electrospray Mass spectrometry results when MeLin is electrosprayed as a sample and LiCl is dropped as an ionizing agent near the cone opening of the mass analyzer Mass spectrometry results when electro-spraying MeLin as a sample Mass spectrometry result when electrospray is mixed with MeLin of sample and LiCl of ionizing agent Mass spectrometry results when electrospraying carbamazepine as a sample and dropping LiCl as an ionizing agent near the needle tip of the electrospray Mass spectrometry results when electrospraying carbamazepine as a sample and dropping LiCl as an ionizing agent near the cone opening of the mass analyzer Mass spectrometry results when electrospraying carbamazepine as a sample Mass spectrometric results when etofenprox is electrosprayed as a sample and LiCl is dropped as an ionizing agent near the needle tip of the electrospray Mass spectrometric results when etofenprox is electrosprayed as a sample and LiCl is dropped as an ionizing agent near the cone opening of the mass spectrometer Mass spectrometric results when etofenprox was electrosprayed as a sample

Claims (7)

A method of adding an ionizing agent, characterized in that a liquid sample is sprayed from a needle of an electrospray device and an ionizing agent droplet is added before the sample is introduced into a mass spectrometer. How to add. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is dropped near the tip of the needle. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is dropped between the needle and a mass analyzer cone opening. 2. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is dropped in the vicinity of the mass analyzer cone opening. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is held at the tip of a syringe and is disposed in the vicinity of the tip of the needle. 2. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is held at a tip of a syringe and disposed between the needle and a mass analyzer cone opening. The method of adding an ionizing agent according to claim 1, wherein the ionizing agent droplet is held at a tip of a syringe and disposed in the vicinity of the mass analyzer cone opening.

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