JPH11160296A - Liquid chromatographic mass spectrograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a salt or the like in a buffer liquid for causing a contamination of an MS unit. SOLUTION: A sample liquid channel 30 and a pure water channel 31 are arranged via an ion permeable film 32 for fixing an ion capturable substance 32a having selectivity to ion to be removed. When a voltage is applied to electrodes 33, 34 respectively provided in the channels 30, 31, positive ion containing K<+> to be removed is attracted to the electrode 34 and moved toward the film 32. Only the K<+> is captured to the substance 32a, and further drawn to the channel 31 side according to a potential difference. Thereafter, the K<+> is carried out by a flow of the pure water. Thus, only the ion for causing a contamination can be removed without influence to the ion of the sample component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid chromatograph mass spectrometer (LC / MS), and more particularly to a liquid chromatograph mass spectrometer for performing chromatographic analysis using a buffer containing salts as a mobile phase.
Regarding C / MS.

[0002]

2. Description of the Related Art FIG. 2 is a schematic diagram showing an example of a general LC / MS. Liquid chromatograph (LC) part 1
Reference numeral 0 denotes a liquid sending section 11 for sending a mobile phase, a sample injection section 12 for injecting a sample into the mobile phase, a separation column 13, and a detector 14 for detecting components in an eluate from the column 13. Is done. The liquid sending section 11 sends out a mobile phase such as water or an organic solvent at a predetermined flow rate to the column 13, and the sample injection section 12 injects a predetermined amount of sample liquid into the mobile phase. Column 13
When passing through the column, each sample component in the sample solution is temporally separated and elutes sequentially from the outlet of the column 13. The detector 14 is, for example, a spectrophotometer or the like, and detects each sample component contained in the eluate. The eluate that has passed through the detector 14 is sent to a mass spectrometry (MS) unit 20. It should be noted that the eluate from the column 13 may be directly sent to the MS unit 20 without providing the detector 14.

In the MS section 20, the eluate is supplied to a nozzle 22
, The sample component molecules contained in the eluate are ionized. The generated ions are introduced into an analysis chamber 23 maintained in a high vacuum, and sent to a central space of a quadrupole filter 24 composed of four rod electrodes.
A voltage in which an AC voltage and a DC voltage are superimposed is applied to the quadrupole filter 24, and only ions having a specific mass number (mass m / charge z) corresponding to this voltage pass through the quadrupole filter 24. To reach the ion detector 25. In the ion detector 25, a current corresponding to the number of reached ions is extracted.

[0004]

In the LC section 10, various separation modes such as distribution, adsorption, ion exchange, and gel are used to separate sample components, and a column 13 suitable for the mode is selected. In ion exchange chromatography,
Effective pH for separation depending on the type of stationary phase (ion exchanger)
And the retention value of the sample component changes depending on the pH of the mobile phase. For this reason, various buffers are used to properly adjust the pH of the mobile phase. Also, in other chromatographs such as adsorption, when analyzing a sample that dissolves only in a specific pH range, such as a biological sample, an appropriate buffer is used.

However, in the LC / MS, if a buffer containing salts such as a phosphate buffer is used as a mobile phase in the LC section 10, when the MS section 20 ionizes, the salts precipitate and the ionization chamber 21. Pollution inside. Especially when a high concentration of buffer is used, the contamination is severe and the analysis cannot be continued. To prevent this,
It is necessary to remove the above salts while the eluate is being sent from the LC unit 10 to the MS unit 20 (position A in FIG. 2).

Conventionally, as a method of removing such salts, for example, a method of vaporizing an eluate and collecting salts remaining as a solid is known. However, in such a method, not only salts to be removed but also sample components to be analyzed are removed at the same time. For this reason, the concentration of the sample component becomes extremely low, and there is a possibility that the analysis accuracy is largely deteriorated. Further, the above-described salt removing apparatus is large-scale and requires a large cost. For this reason, it is practically impossible to remove salts, and L
For C / MS, buffers containing salts (especially high concentration buffers)
Cannot be used as a mobile phase, and as a result, the types of samples that can be analyzed are limited.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid chromatograph mass spectrometer capable of utilizing various high-concentration buffers as a mobile phase. To provide.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a liquid chromatograph comprising a salt removing means before introducing a sample liquid separated in a liquid chromatograph into a mass spectrometer. In the graph mass spectrometer, the salt removing means comprises: a) a sample solution flow path through which a sample solution having a buffer containing salts as a mobile phase flows, and b) an ion-trapping substance corresponding to an ion to be removed is fixed. A liquid flow path or a liquid tank arranged adjacent to the sample liquid flow path with the ion permeable membrane interposed therebetween; andc) voltage applying means for generating a predetermined potential difference on both sides of the ion permeable membrane. , Are provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a sample solution passing through the sample solution channel, salts are dissolved and separated into positive ions and negative ions. For example, when it is desired to remove a specific positive ion therein, an ion permeable membrane on which an ion-trapping substance having a property of selectively taking in only that ion is used is used. In this case, the voltage applying means applies a voltage such that the potential of the liquid flow path or the liquid tank side is lower than that of the sample liquid flow path side with the ion permeable membrane interposed therebetween. Positive ions (including those other than those due to the above salts) existing in the sample liquid flow path gather near the ion-permeable membrane along the potential gradient. The ion-trapping substance selectively takes in only the positive ions to be removed among the positive ions, and the taken-in positive ions fly out to the liquid flow path or the liquid tank side with a lower potential. That is, only positive ions to be removed pass through the ion-permeable membrane, and other positive ions remain in the sample liquid flow path. Note that if the concentration of the positive ions to be removed in the liquid on the liquid flow path or the liquid tank side is extremely low, the positive ions once flowing into the liquid flow path or the liquid tank side move the ion permeable membrane in the opposite direction. Never pass.

[0010]

As described above, according to the liquid chromatograph mass spectrometer according to the present invention, undesired salts can be efficiently and selectively removed at the time of mass spectrometry by a simple configuration before the mass spectrometer. Can be removed. For this reason, various buffers having a high concentration, which were conventionally difficult to use as the mobile phase of the liquid chromatograph, can be freely selected according to the sample to be analyzed, so that there are no restrictions on the substances that can be analyzed. . Further, even when the salts are removed, the concentration of the sample component does not decrease, so that high analysis accuracy can be maintained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a liquid chromatograph mass spectrometer according to the present invention will be described with reference to FIG. FIG. 1 shows a liquid chromatograph mass spectrometer according to the present embodiment.
It is a block diagram of the salt removal means provided between S parts.
In this example, it is assumed that the mobile phase of the LC part is water, and an appropriate amount of potassium phosphate (K ₃ PO ₄ ) is added as a buffer.

In this salt removing means, the sample liquid flow path 30 through which the eluate from the column 13 flows and the pure water flow path 31 through which pure water flows are adjacent to each other with an ion permeable membrane 32 extending in the flow direction. It is arranged. The ion permeable membrane 32 is
For example, an ion-trapping substance 32a having selectivity for ions to be removed is immobilized on a membrane made of a hydrophobic substance (solid or liquid) such as oils and fats and organic solvents. For example, as the ion-trapping substance for positive ions, for example, crown ethers and complexes thereof can be used. Crown ethers are macrocyclic compounds having heteroatoms such as oxygen, nitrogen, and sulfur as electron-donating atoms, and the electron-donating atoms easily take in positive ions into polar vacancies generated when they face the inside of the ring. . It has high selectivity for specific ions depending on the compatibility between the pore diameter and the positive ion radius. Here, a crown ether having high selectivity for potassium ions (K ⁺ ) is used as the ion-trapping substance 32a.

Plate-shaped electrodes 33 and 34 are disposed on both sides of the ion permeable membrane 32, and a predetermined voltage V is applied to both electrodes 33 and 34 by a DC power supply 35. As a result, an electric field having a potential gradient that is inclined downward from the electrode 33 toward the electrode 34 is formed between the electrodes 33 and 34 with the ion permeable film 32 interposed therebetween. The voltage V can be determined as appropriate, but generally 100 V or less is sufficient.

In the eluate flowing through the sample liquid flow path 30,
There are potassium ions (K ⁺ ) and phosphate ions (PO ₄ ⁻ ) generated by separation of potassium phosphate as a buffer, and various ions generated from sample components to be analyzed. Due to the potential gradient as described above, positive ions having a positive charge move toward the ion permeable membrane 32, while negative ions having a negative charge move toward the electrode 33.
Ion-trapping substance 3 fixed to ion-permeable membrane 32
2a takes in only potassium ions from the sample liquid flow path 30 side into the inside. Since the surface of the ion permeable membrane 32 on the side of the pure water channel 31 is at a lower potential than the surface of the sample liquid channel 30, the potassium ions taken into the ion-trapping substance 32a are attracted to the electrode 34 and Jump out to 31 side. That is, potassium ions pass through the ion-permeable membrane 32 via the ion-trapping substance 32a. Since pure water flows at a predetermined flow rate in the pure water flow path 31, potassium ions that have flowed out toward the pure water flow path 31 are carried away by the flow of pure water. Since the ion density is always lower on the pure water flow path 31 side than on the sample liquid flow path 30 side, potassium ions do not pass through the ion permeable membrane 32 in the reverse direction and return to the sample liquid flow path 30. .

Since even positive ions, other than potassium ions, are not taken into the ion-trapping substance 32a, they do not pass through the ion-permeable membrane 32. Therefore, positive ions other than potassium ions and negative ions gathered in the vicinity of the electrode 33 are pushed by the flow of the continuously supplied eluate to form M ions.
The process proceeds to the S section 20 side. For this reason, sample components other than salts of the buffer are introduced into the MS unit 20 without reduction.

In the above embodiment, only potassium in the potassium phosphate buffer is removed, and phosphate ions remain in the eluate. However, it is alkali metals such as potassium and calcium that precipitate during ionization in the MS section 20 and cause contamination, so that the contamination can be prevented by removing these ions. .

When it is desired to remove negative ions, it is possible to remove them by the same method using an ion-permeable membrane on which an ion-trapping substance for selectively taking in the negative ions is fixed. Of course, if two types of ion permeable membranes, each of which fixes an ion-trapping substance for positive ions and an ion-trapping substance for negative ions, are used together, positive ions and negative ions can be removed simultaneously. It is also possible to simultaneously remove a plurality of types of positive ions or negative ions using a plurality of ion-permeable membranes having different selectivities.

The embodiment described above is merely an example, and it is apparent that modifications and modifications can be appropriately made in accordance with the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of a salt removing unit in a liquid chromatograph mass spectrometer according to the present invention.

FIG. 2 is a schematic configuration diagram of a general liquid chromatograph mass spectrometer.

[Explanation of symbols]

 Reference numeral 30: sample liquid flow path 31: pure water flow path 32: ion permeable membrane 33, 34: electrode 35: DC power supply

Claims (1)

[Claims] 1. A liquid chromatograph mass spectrometer comprising a salt removing means before introducing a sample liquid separated by a liquid chromatograph section into a mass spectrometric section, wherein the salt removing means comprises: a) a buffer containing salts; The sample liquid flow path through which the sample liquid having the liquid as the mobile phase flows, and b) the sample liquid flow path is disposed adjacent to the sample liquid flow path with an ion-permeable membrane fixed with an ion-trapping substance corresponding to the ion to be removed. A liquid chromatograph mass spectrometer, comprising: a liquid flow path or a liquid tank provided; and c) voltage applying means for generating a predetermined potential difference on both sides of the ion permeable membrane.