JP4174623B2 - Liquid chromatograph mass spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid chromatograph mass spectrometer (hereinafter abbreviated as LC / MS), and more particularly to an improvement in an interface unit of a liquid chromatograph mass spectrometer using an electrospray method.
[0002]
[Prior art]
In LC / MS, a method may be used in which components separated in a liquid chromatograph are ionized under atmospheric pressure and introduced into a mass spectrometer. In this case, an interface for ionizing components separated by the column of the liquid chromatograph section is necessary. A typical interface generally used in LC / MS is an electrospray ionization (hereinafter abbreviated as ESI) method.
In the ESI method, a sample solution is sent to the tip of a thin nozzle, and a high voltage is applied to the tip of the nozzle. As a result, a strong unequal electric field is formed at the nozzle tip, and the liquid sample is sprayed as a charged droplet by this strong electric field, and further, the droplet breaks up due to the Coulomb repulsive force of the ions in the droplet and ionizes. Is done.
FIG. 4 is a diagram showing a general configuration of an LC / MS using the conventional ESI method, in which 10 is a liquid chromatograph unit, 20 is a mass spectrometer unit, and 30 is an interface unit. The interface unit 30 includes an electrospray ionization unit 31 having an electrospray probe 31a, and ionization is performed by applying a high voltage to the probe 31a. Since a high voltage is applied to the electrospray probe 31a, the electrospray probe 31a is held so as to be electrically insulated from the wall surface that supports it. Further, a heater mechanism (not shown) is attached to the pipe 32 provided at the subsequent stage of the electrospray ionization unit 31, and the charged droplets generated by the electrospray ionization unit 31 are mass-decomposed as minute droplets while being desolvated. It is sent to the analysis unit 20.
[0003]
FIG. 2 is a diagram showing a configuration of a conventional electrospray ionization unit (portion 31 in FIG. 5). In the figure, 11 is a glass capillary connected to the column outlet of the liquid chromatograph section 10, 12 is a metal capillary, and 13 is a nebulization tube. The glass capillary 11 is fitted into the metal thin tube 12, and the glass capillary 11 protrudes from the end of the metal thin tube 12 on the end side (blowing side). A nebulization tube 13 is loosely inserted into the metal thin tube 12 with an appropriate gap, and the metal thin tube 12 and the nebulization tube 13 are held in a state where they are electrically connected to each other by a tightening nut 16 and a metal ferrule 17 on the proximal end side. I have to do it. The metal ferrule 17 is hermetically sealed so that gas does not leak from the base end side. Reference numeral 15 denotes an electrically non-conductive resin tube, whereby the nebulization tube 13 is electrically insulated from the casing (the tightening nut 16 and metal on the nebulization gas inlet 14 side described later) It is configured to be electrically insulated from the casing by the same configuration as the ferrule and the resin tube 15). The nebulization tube 13 is held so as not to be in electrical contact with the housing so as to be supported on the wall surface at the position of the resin tube 15.
Further, a nebulization gas such as nitrogen gas is blown into the gap between the nebulization tube 13 and the metal thin tube 12 from the nebulization gas introduction port 14 on the base end side (column side), and is ejected from the outer periphery of the end of the metal thin tube 12. is there. Reference numeral 18 denotes a high voltage generator, which can apply a high voltage of several kV to the metal thin tube 12 through the nebulizing tube 13, the metal ferrule 16, and the tightening nut 17.
In the electrospray ionization unit 31 having such a configuration, when the sample solution is sent from the liquid chromatograph unit 10, the nebulization gas is introduced from the nebulization gas introduction port 14 and a high voltage is further applied to the metal thin tube 12. Then, the sample solution introduced into the glass capillary 11 is charged and sprayed as charged droplets from the end of the glass capillary 11 by being assisted by the nebulizing gas. Charged droplets collide with the surrounding gas to promote desolvation and generate ions. At this time, in principle, ionization proceeds by the Coulomb repulsive force without supplying nebulizing gas, but by supplying nebulizing gas, ionization is accelerated and a large amount of sample solution can be ionized stably and rapidly.
[0004]
[Problems to be solved by the invention]
In the conventional electrospray ionization part, the metal thin tube 12 and the nebulization tube 13 are loosely inserted while maintaining an appropriate gap as described above, and nebulization gas is ejected from the gap. Therefore, since the metal thin tube 12 is only held on one side (base end side) with respect to the nebulization tube 13, the outlet of the nebulization tube 13 and the outlet of the glass capillary 11 on the other end side (terminal side) Instead of concentric circles, the arrangement is eccentric to one side as shown in FIG. That is, since the metal thin tube 12 cannot be stably held with respect to the nebulizing tube 13 due to the presence of the gap portion, it is inevitably eccentric. As a result, the spray direction from the glass capillary 11 is deviated from the axial direction of the pipe 32, resulting in a non-uniform spray state, which affects the reproducibility and stability of analysis.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid chromatograph mass spectrometer having a probe structure in which the position of an electrospray probe can be easily adjusted and in which eccentricity is unlikely to occur, so that stable analysis can be performed.
[0006]
[Means for Solving the Problems]
The liquid chromatograph mass spectrometer of the present invention made to solve the above problems is a liquid chromatograph mass spectrometer that performs ionization by spraying a sample solution as charged droplets by an electrospray ionization unit. A capillary into which the sample solution is inserted, a metal thin tube provided by inserting the capillary, a power source for applying a high voltage to the metal thin tube, and the metal thin tube while holding the metal thin tube on the proximal side. And a nebulizing tube provided with a nebulizing gas introduction port on the proximal end side, and a spiral spacer wound around a gap between the metal thin tube and the nebulizing tube.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an electrospray ionization unit used for LC / MS according to an embodiment of the present invention. The overall configuration of the LC / MS is the same as that of FIG.
In FIG. 1, 11 is a glass capillary, 12 is a metal thin tube, 13 is a nebulization tube, 14 is a nebulization gas inlet, 15 is a resin tube, 16 is a metal ferrule, 17 is a tightening nut, and 18 is a high voltage generator. Since these parts also have the same structure as that of the conventional example of FIG.
In the electrospray ionization section 31 of the present invention, the spiral spacer 20 is wound around the gap between the metal thin tube 12 and the nebulization tube 13 which become the flow path of the nebulization gas. The spiral spacer 17 is wound at a pitch that does not cause resistance when gas flows in the gap. As a material of the spiral spacer, for example, a SUS wire is suitable, but any conductive material may be used. The conductive material is more reliable electrical contact between the nebulization tube 13 (preferably made of aluminum for ease of processing) and the metal thin tube 12 (preferably made of SUS) via the spiral spacer 17. It is because it can be made to be kept at.
[0008]
In this electrospray ionization section, when the sample solution is sent to the glass capillary 11, nitrogen gas is sent from the nebulization gas inlet 14 and an appropriate high voltage is applied to the nebulization tube 13 from the high voltage power supply 18. The fed nitrogen gas advances in the spiral direction along the spiral spacer 20 and is ejected from the terminal outlet. On the other hand, the high voltage applied to the nebulization tube 13 is also reliably applied to the metal thin tube 12 through the spiral spacer 20. Then, the sample solution that has flowed through the glass capillary 11 according to the principle of the electrospray method is sprayed as charged droplets. At this time, the blowout port of the glass capillary 11 and the metal thin tube 12 is coaxially arranged with the nebulization tube 13 due to the presence of the spiral spacer 20, so that the blowout direction is not decentered and is blown out in the axial direction.
[0009]
Embodiments of the present invention are summarized below.
(1) In a liquid chromatograph mass spectrometer that performs ionization by spraying a sample solution as charged droplets by an electrospray ionization unit, the electrospray ionization unit inserts a capillary into which the sample solution is inserted and the capillary A thin metal tube, a power source for applying a high voltage to the thin metal tube, and a nebulization tube that is loosely inserted while holding the thin metal tube on the proximal end side and provided with a nebulization gas inlet on the proximal end side, A liquid chromatograph mass spectrometer comprising a spiral spacer made of an electrically conductive material wound around a gap between the metal thin tube and the nebulize tube. In this embodiment, the nebulization tube, the metal thin tube, and the glass capillary are coaxially arranged and the flow path of the nebulization gas is maintained, but the electrical contact between the nebulization tube and the metal thin tube is ensured. Can do.
[0010]
【The invention's effect】
As described above, in the LC / MS of the present invention, since the spiral spacer is provided in the gap between the nebulization tube and the metal thin tube of the electrospray probe, the metal thin tube and the glass capillary are not eccentric with respect to the nebulization tube. It can be easily attached and nebulization gas can be ejected from the end of the nebulization tube.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an electrospray ionization unit used for LC / MS according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an electrospray ionization unit used for conventional LC / MS.
FIG. 3 is a partially enlarged view of FIG. 3;
FIG. 4 is an overall configuration diagram of LC / MS.
[Explanation of symbols]
11: Glass capillary 12: Metal thin tube 13: Nebulizing tube 14: Nebulizing gas inlet 15: High voltage generator 17: Spiral spacer

Claims (1)

In a liquid chromatograph mass spectrometer that performs analysis by spraying a sample solution as charged droplets in an electrospray ionization unit and performing ionization,
The electrospray ionization section includes a capillary into which a sample solution is introduced,
A metal thin tube provided so as to fit the capillary,
A power source for applying a high voltage to the metal thin tube;
While slowly inserting the metal thin tube while holding the proximal side, a nebulizing tube provided with a nebulizing gas introduction port on the proximal side,
A liquid chromatograph mass spectrometer comprising a spiral spacer wound around a gap between the metal thin tube and the nebulization tube.

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