JP3201226B2 - Liquid chromatograph mass spectrometer - Google Patents

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 (hereinafter referred to as "LC / MS"), and more particularly to an interface between a liquid chromatograph unit and a mass spectrometric unit of LC / MS.

[0002]

2. Description of the Related Art In LC / MS, components separated in a liquid chromatograph section are ionized and introduced into a mass spectrometry section. Therefore, an interface for ionizing the separated components is needed. Interfaces generally used for LC / MS include electrospray interface (ESI) and atmospheric pressure chemical ionization interface (A
PCI).

In the ESI method, a liquid sample 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 non-uniform electric field is formed at the tip of the nozzle, and the liquid sample is sprayed as a charged droplet by the strong electric field. Is performed.

On the other hand, in the APCI method, a liquid sample is forcibly sprayed by a gas flow in a nebulizer (atomizer), and the liquid sample is desolvated by heating the liquid sample. The sample is ionized (chemical ionization). FIG. 2 shows a conventional LC /
It is a figure showing the general composition of MS. Reference numeral 10 denotes a liquid chromatograph unit, and reference numeral 20 denotes a mass spectrometric unit. Reference numeral 30 denotes an interface unit. The interface unit shown in this figure has an electrospray ionization unit 31 using the ESI method and a pipe 32 to which a heater mechanism (not shown) is attached. Electrospray probe 31 of electrospray ionization unit 31
a is fixed by the fixing member 33. The fixing member 33 has a fixed position with respect to the pipe 32. In this drawing, a housing shared with the mass spectrometer is used as the fixing member 33. The electrospray probe 31a has a thin tube through which the sample liquid sent from the liquid chromatograph unit 10 passes. The tip of the electrospray probe 31a on the side facing the pipe 32 has a needle shape. It is to be spouted from the part. Then, an electrospray probe 3 is supplied from a high voltage generating circuit (not shown).
A high voltage of about several KV is applied to 1a. With this setting, the liquid sample sent from the liquid chromatograph unit 10 is drawn out in a spray form by the strong electric field formed near the nozzle at the tip of the needle, and the pipe 3
Enter 2.

When the ESI method is used, the distance between the pipe 32 and the tip of the needle of the electrospray probe 31a is set to be short, and the electrospray is performed so that more charged microdroplets enter the pipe 32. The spray probe 31a is fixed to the fixing member 33. The charged microdroplets are heated by a heater in the pipe 32 to evaporate the solvent, and further collide with other particles to be further miniaturized to promote ionization. Mass spectrometry unit 2
Sent to 0.

On the other hand, when performing ionization by the APCI method, an atmospheric pressure chemical ionization unit 34 as shown in FIG. 3 is attached instead of the electrospray ionization unit 31 of FIG. That is, a probe 34 having a thin tube through which a sample liquid passes and having a needle-like tip.
a, an atmospheric pressure chemical ionization unit 34 including an atomization chamber 34b provided so as to surround a needle portion of the probe 34a, and a discharge electrode 34c attached to a front surface of an opening of the atomization chamber.
Is attached. The atomization chamber 34b is heated by a heater (not shown), and a voltage of several KV is applied to the discharge electrode 34c. By doing so, the liquid sample sent from the liquid chromatograph unit 10 is separately injected into the atomization chamber 34b from the nozzle at the needle tip of the probe 34a by the atomization gas from the gas line connected to the probe. After being sprayed and desolvated by the heater, it is ionized by contact with buffer ions generated at the discharge electrode. Then, the generated ions are sent to the mass spectrometry unit 20 via the heated pipe 32 while ionization is promoted in the same manner as in the above-described ESI method.

[0007]

In the conventional LC / MS, the electrospray ionization section 31, the atmospheric pressure chemical ionization section 34, or any other ionization section using a spray (such as a sonic spray),
Ions generated in the ionization section, charged microdroplets, etc., pass through a straight pipe formed in the subsequent stage of the ionization section,
At that time, the ionization was promoted and sent to the next stage mass spectrometer.

However, in this case, not only ions but also neutral droplets and charged microdroplets (particles larger than ions) pass through the pipe, and the effect of these particles becomes background noise. Appeared and had an adverse effect.

In order to remove such noises, the pipe axis and the skimmer center line of the mass spectrometer are arranged so as to be displaced from each other, or the center axis of the mass spectrometer is adjusted using an ion focusing lens of the mass spectrometer. It has been devised to shift or remove ions other than the target particles in the ion detector.

[0010] However, even if noise can be reduced by off-axis in the mass spectrometer, these neutral particles and charged microdroplets are introduced into the mass spectrometer and cause contamination. Had been lost.

[0011] The present invention solves the above-mentioned problems, and easily removes noise due to particles other than ions serving as target particles such as neutral particles and charged microdroplets, and does not cause contamination of the mass spectrometer. It is an object of the present invention to provide an LC / MS that has been optimized.

[0012]

According to a liquid chromatograph of the present invention, which has been made to solve the above-mentioned problems, a liquid sample provided from a liquid chromatograph is provided between a liquid chromatograph and a mass spectrometer. In a liquid chromatograph mass spectrometer provided with an interface section which is ionized and provided to a mass spectrometry section, a sample formed by a block having a bent pipe or a bent pipe is provided at a stage subsequent to the ionization section of the interface section. An introduction path is provided, and the inlet side end of the sample introduction path is attached so as to be located in a space where the charged droplets of the ionization section are sprayed, and ions passing through the sample introduction path are detected by the mass spectrometry section. It is characterized by doing so.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the LC / MS of the present invention, a bent sample introduction path is provided in the interface section after the ionization section, so that particles passing through the sample introduction path collide with the inner wall. It will be. Among the collided particles, the ions have a small mass and are immediately sent to the mass spectrometer by being attracted by the electric field. On the other hand, charged microdroplets and neutral particles having a large mass other than the ions that are the target particles adhere to the inner wall for a while when they collide with the inner wall, but are vaporized due to the influence of heating, etc. Since they are discharged differently, they do not directly reach the detection unit of the mass spectrometry unit. Therefore, neutral particles and charged microdroplets having a large mass no longer reach the detection unit, and noise can be removed.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an LC / MS showing one embodiment of the present invention. In addition, about the same thing as a conventional example, FIG.
The description is omitted by attaching the same reference numerals to 3.

As shown in the figure, the interface unit 30
The electrospray ionization unit 31 is fixed to a fixing member 33 using a housing of the mass analysis unit 20.
A bent pipe 35 as a sample introduction path to the mass spectrometry unit 20 is attached to a position near the nozzle portion at the needle tip of the electrospray probe 31a of the electrospray ionization unit 31. This pipe 3
It is desirable that the heater 5 is provided with a heater (not shown).

In this apparatus, the liquid chromatograph unit 10
Is sent to the electrospray ionization section 31 via the column, and the electrospray ionization section 31
Is charged in the pipe 35,
In the case of collision with other molecules or heating, the particles are further miniaturized through desolvation by heating and the like to generate ions. At this time, along with the ions, neutral droplets and charged microdroplets that could not be completely turned into the ions simultaneously enter the pipe 35. However, since the pipe 35 is bent, these particles collide with the inner wall as shown in FIG. 4 and adhere to the inside of the pipe. The attached droplets eventually evaporate and detach from the tube wall,
The gas is exhausted by the exhaust system of the mass spectrometer 20. Therefore, there is no invasion after the gap, and no contamination occurs. On the other hand, the generated ions are attracted by the electric field of the mass spectrometry unit 20, enter after the gap, are introduced into the quadrupole through the ion focusing lens, and are detected by the detector.

FIGS. 6 and 7 show baseline data when a conventional straight pipe is used and when a bent pipe is used. In this measurement, a sample in which a 1% acetic acid aqueous solution and methanol were mixed at a ratio of 1: 1 was used, and the horizontal axis was the time axis (full scale about 1 minute) and the vertical axis was the detection signal intensity. The measurements were made under the same measurement conditions.
Comparing these results, it can be seen that baseline noise is reduced when using a clearly bent pipe.

Note that the bent shape of the pipe of this embodiment is an example, and a pipe having a smooth curved shape may be used, for example. In short, the present invention can be implemented if it is different from a straight pipe. Further, a block having a bent pipe as shown in FIG. 5 may be used instead of the pipe. However, whether it is a pipe or a block, if it is bent extremely, the ionic strength will be affected.
It is necessary to have a moderate bending.

In this embodiment, the noise removal is not performed on the mass spectrometer side. However, the noise elimination is further improved by using the conventional noise elimination performed on the mass spectrometer side. And contamination of the mass spectrometer can be prevented.

[0020]

As described above, as described above, the LC / M according to the present invention is used.
In S, a bent sample introduction path is provided in the interface section, and ions are sent to the mass spectrometry section through this introduction path, so that noise due to neutral particles and charged particles that are not ionized can be removed, and mass There is no contamination of the analysis section. Furthermore, since the alignment of the pipe and the gap of the mass spectrometric section may be performed by aligning the axes, there is no nervousness during assembly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid chromatograph mass spectrometer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram (ESI method) of a conventional liquid chromatograph mass spectrometer.

FIG. 3 is a configuration diagram (APCI method) of a conventional liquid chromatograph mass spectrometer.

FIG. 4 is a diagram illustrating a state in which charged microdroplets collide in a pipe.

FIG. 5 is a diagram of a sample introduction path (block) used in a liquid chromatograph mass spectrometer according to another embodiment of the present invention.

FIG. 6 is a diagram of a baseline when a straight pipe is used.

FIG. 7 is a diagram of a baseline when a bent pipe is used.

[Explanation of symbols]

 10: Liquid chromatograph unit 20: Mass spectrometry unit 30: Interface unit 31: Electrospray ionization unit 33: Fixed member 34: Atmospheric pressure chemical ionization unit 35: Bent pipe

Claims (1)

(57) [Claims] 1. A liquid chromatograph / mass spectrometer having an interface between a liquid chromatograph section and a mass spectrometric section, the interface section ionizing a liquid sample supplied from the liquid chromatograph section and supplying the ionized sample to the mass spectrometric section. At the subsequent stage of the ionization section of the interface section, there is provided a sample introduction path formed by a block having a bent pipe or a bent pipe. A liquid chromatograph mass spectrometer, which is mounted so as to be located in a space to be sprayed, wherein ions passing through a sample introduction path are detected by a mass spectrometer.