JP2001272375A - Liquid chromatograph-mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid chromatograph-mass spectrometer, capable of accurate analysis by reducing noise and lowering memory effects in a high concentration sample. SOLUTION: In an atomizing chambers 21, a spray nozzle 211 is arranged so that its jetting direction is directed parallel to the inlet side central axis of desolvating tube 23 and oppositely to the droplet advancing direction inside the solvent removal tube 23 (that is, in the antiparallel direction). A jetting port of the spray nozzle 211 is arranged in the substantially same position as the inlet side tip of the desolvating tube 23, and a semispherical recessed-face guide 261 is arranged in front of them. A drain is arranged below a recessed- face guide 261. A sample droplet jetted from the jetting port of the spray nozzle 211 is not introduced into the solvent removal tube 23 directly but is moved in the opposite direction along the recessed-face guide 261, so as to be led to the inlet of the solvent removal tube 23. In this case, small droplets float on the air flow flowing along the recessed-face guide 261 to be led to the inlet of the solvent removal tube 23, while a large droplet collides against the surface of the recessed-face guide 261 to condense and flows downward along the recessed-face guide 261.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid chromatograph mass spectrometer (hereinafter referred to as "LC / MS").

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing an example of a general LC / MS. Liquid chromatograph (LC) unit 10
The liquid sample that is temporally separated and eluted from the column 11 is introduced into the interface section 20 and the spray nozzle 21
Is sprayed into the atomization chamber 22 and ionized. The generated ions are sent to the MS unit 30 through a desolvation tube 23 such as a heated capillary positioned in front of the ions.

The MS section 30 comprises three chambers, a first intermediate chamber 31, a second intermediate chamber 32, and an analysis chamber 33.
The desolvation pipe 23 is provided between the first intermediate chamber 3 and the intermediate chamber 31.
A skimmer 35 having a very small diameter passage hole (orifice) is provided between the first and second intermediate chambers 32, respectively.
The interior of the atomization chamber 22 is maintained at approximately atmospheric pressure, and the first intermediate chamber 31
Is evacuated to about 1 Torr by a rotary pump, and the second intermediate chamber 32 and the analysis chamber 33 are evacuated to about 10 ^-3 to 10 ^-4 Torr and about 10 ^-5 to 10 ^-6 Torr by a turbo molecular pump, respectively. Thus, the degree of vacuum gradually increases from the atomization chamber 22 toward the analysis chamber 33.

[0004] The ions that have passed through the desolvation tube 23 as described above are converged on the orifice of the skimmer 35 by the deflector electrode 34 and are introduced into the second intermediate chamber 32 through the skimmer 35. Then, it is converged and accelerated by the ion lens 36 and sent to the analysis chamber 33, and only the target ions having a specific mass number (mass m / charge z) are analyzed.
It passes through a quadrupole filter 37 arranged in 3 and reaches a detector 38. The detector 38 extracts a current corresponding to the number of ions that have arrived.

The interface section 20 generates gas ions by atomizing a liquid sample by heating, high-speed gas flow, high electric field, and the like. The interface section 20 uses an atmospheric pressure chemical ionization method (APCI) or an electrospray ionization method (APCI). ES
I) is the most widely used. In the APCI, a needle electrode is arranged in front of the tip of the spray nozzle 21, and carrier gas ions (buffer ions) generated by corona discharge from the needle electrode on droplets of the liquid sample atomized by heating in the spray nozzle 21. Are chemically reacted to perform ionization. On the other hand, in ESI, the spray nozzle 21
A high voltage of about several kV is applied to the tip of the device to generate a strong uneven electric field. The liquid sample is separated into electric charges by this electric field, and is torn off and atomized by Coulomb attraction. The solvent in the droplets evaporates upon contact with the surrounding air, generating gaseous ions.

In either of the above-mentioned APCI and ESI methods, as shown in FIG. 5A, the fine droplets containing the generated ions are supplied with the momentum when ejected from the spray nozzle 21 and the atomizing chamber 22 and the Due to the above-mentioned pressure difference between the first intermediate chamber 31 and the intermediate chamber 31, the liquid enters the desolvation pipe 23. Desolvation tube 2
3 is heated, and the fine droplets passing therethrough evaporate the solvent due to heat, and as the droplet size decreases, spontaneous droplet destruction due to Coulomb repulsion further progresses and is ionized. You.

[0007]

Ideally, the solvent in the fine droplets sprayed from the spray nozzle 21 completely evaporates in the desolvation pipe 23, and only the ions remain in the first intermediate chamber 31.
The mass spectrometry should proceed to the subsequent steps, but in practice, some of the fine droplets become smaller, but the first droplet remains in the droplet state.
It proceeds to the intermediate chamber 31 and the skimmer 35 and thereafter, enters the detector 38 and generates spike noise.

In order to reduce such noise, various measures have been taken for the desolvation pipe 23 and the positional relationship between the desolvation pipe 23 and the spray nozzle 21. FIG. 5 (b)
In both cases (c) and (c), the droplets are not directly sprayed toward the desolvation tube 23. In (b), the spray direction is oblique to the central axis of the desolvation tube 23.
In (c), the spray nozzles 21 are arranged orthogonally. However, as described above, the droplet is not necessarily absorbed by not only the momentum due to the spraying but also the pressure difference between the two chambers. Therefore, these sufficiently prevent the droplet from entering the next chamber (the first intermediate chamber 31). It is not possible.

Therefore, as shown in FIG. 5D, the desolvation pipe 24 is bent at 90 ° and the spray nozzle 2
A method has been devised in which the spray direction 1 is orthogonal to the central axis on the inlet side of the desolvation pipe 23. According to this, the droplets that have entered the desolvation tube 24 are temporarily removed from the desolvation tube 2 at the bent portion.
Because of the collision with the tube wall of No. 4, the number of droplets that go straight and directly enter the next chamber can be significantly reduced.

However, the configuration shown in FIG. 5D has the following problems. First, the spray nozzle 21
Is located near the partition 25 with the next chamber, the partition 25 is contaminated by the sample droplet sprayed from the spray nozzle 21. In LCMS in which the components of a sample change from moment to moment, contamination by a component at one point in time affects the analysis of the component at the next point in time (so-called memory effect).
This appears as a tail in the latter half of the component peak in the chromatograph, and prevents accurate analysis of the sample. Also,
Since the partition wall 25 is contaminated, it must be appropriately cleaned before analyzing another sample. Further, since the spray direction is perpendicular to the partition wall 25, the sprayed droplet collides with the partition wall 25 and, while rebounding, gathers with nearby droplets to grow into a larger droplet. When such large droplets reach the inlet of the desolvation tube 24 and are sucked, the possibility of reaching the next chamber without vaporization in the desolvation tube 24 increases.

The present invention has been made to solve these problems, and an object of the present invention is to perform accurate analysis while suppressing noise and suppressing memory effects in a high-concentration sample. It is an object of the present invention to provide a liquid chromatograph mass spectrometer that can be used.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a spray nozzle provided in an atomizing chamber, and a desolvation pipe provided on a wall separating the atomizing chamber from the next chamber. In a liquid chromatograph mass spectrometer comprising:
The spray direction of the spray nozzle should be 90 ° or less (including the case of being anti-parallel) with respect to the central axis on the inlet side of the desolvation pipe. The present invention is characterized in that a concave guide extending over the entire surface is provided.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a liquid chromatograph mass spectrometer according to the present invention is basically the same as the conventional one shown in FIG. 4, but the arrangement of spray nozzles in an atomization chamber and the like. It has features. That is, as one configuration example, as shown in FIG. 1, the spray direction of the spray nozzle 211 in the atomization chamber 221 is substantially parallel to the inlet-side central axis of the desolvation tube 23 and the spray direction is
Are arranged so as to be opposite to the traveling direction of the liquid droplets inside (in the above, this is expressed as “anti-parallel”). The outlet of the spray nozzle 211 is arranged at substantially the same position as the front end of the desolvation pipe 23 on the inlet side, and a hemispherical concave guide 261 is provided in front of both. Concave guide 2
Below 61, a drain (drainage port) is provided.

As shown in FIG.
Sample droplets sprayed from the nozzle of
Without entering, the direction of movement is changed in the opposite direction along the concave guide 261, and heads toward the inlet of the desolvation pipe 23. At this time, the small droplets ride on the flow of air flowing along the concave guide 261 and head toward the inlet of the desolvation pipe 23, whereas the large droplets collide with the surface of the concave guide 261 and aggregate to form a concave surface. It flows down along the guide 261.

This prevents large droplets from entering the desolvation tube 23 with a large momentum. Further, since the mist droplets only flow in one direction along the concave guide 261, it is possible to prevent the droplets moving in the opposite direction from being mixed and condensed to enter the desolvation tube.

Further, the inlet of the desolvation pipe 23 is connected to the concave guide 2.
The memory effect can be minimized by appropriately separating from the memory 61. In addition, by providing the drain as shown in FIG. 1, the inside of the atomization chamber 221 can be easily cleaned. That is, the sample adhered to the surface of the concave guide 261 is discharged from the drain by spraying water or a solvent on the concave guide 261 during cleaning.
Hassle-free cleaning.

In FIG. 1, the spray nozzle 211 is disposed above the desolvation pipe 23, but it may be lateral or lower.

FIG. 3 shows another configuration example of the present invention. In this example, the spray direction of the spray nozzle 212 is
Is approximately perpendicular (90 °) to the central axis of the concave surface guide 262, and accordingly, the concave guide 262 is formed into a quarter spherical shape. The operation and effect are the same as described above.

Another advantage of such an arrangement is that the total length of the apparatus (the entire length including the atomization chamber 222 to the analysis chamber 33) can be somewhat shortened. Although the configuration shown in FIG. 1 can reduce the overall length as compared with the conventional device, the configuration shown in FIG. 3 can further reduce the overall length.

In the conventional apparatus shown in FIG. 5 (c), the spray nozzle 21 is arranged so that the spray port is located immediately near (slightly above) the inlet of the desolvation pipe 23, whereas in FIG. In the illustrated apparatus according to the present invention, the direction of movement of the atomized sample droplet is changed and guided by the concave guide 262, so that the spray port of the spray nozzle 212 can be slightly separated from the desolvation pipe 23. This prevents large droplets from being present near the inlet of the desolvation pipe 23, and reduces the probability of being sucked into the desolvation pipe 23 by a differential pressure.

As described above, two configuration examples are shown in FIGS. 1 and 3. As can be easily understood, the angle between the desolvation pipe and the spray nozzle can be set to any angle between them. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid chromatograph mass spectrometer which is one configuration example of the present invention.

FIG. 2 is an enlarged view of an atomization chamber of the liquid chromatograph mass spectrometer.

FIG. 3 is a sectional view of a liquid chromatograph mass spectrometer which is another configuration example of the present invention.

FIG. 4 is a cross-sectional view of a conventional liquid chromatograph mass spectrometer.

FIG. 5 is an explanatory diagram showing a relationship between a spray nozzle and a desolvation pipe of a conventional liquid chromatograph mass spectrometer.

[Explanation of symbols]

 211, 212 ... Spray nozzles 221, 222 ... Atomization chamber 23 ... Desolvation tube 261, 262 ... Concave guide 31 ... First intermediate chamber 32 ... Second intermediate chamber 33 ... Analysis chamber 34 ... Deflector electrode 35 ... Skimmer 36 ... Ion Lens 37 ... Quadrupole filter 38 ... Detector

Claims (1)

[Claims] 1. A spray nozzle provided in an atomization chamber,
In a liquid chromatograph mass spectrometer comprising an atomization chamber and a desolvation pipe provided on a wall separating the next chamber, the spray direction of the spray nozzle is set to 90 ° or less with respect to the inlet-side central axis of the desolvation pipe. A liquid chromatograph mass spectrometer characterized in that a concave guide extending between the spray nozzle and the inlet of the desolvation pipe is provided on the front surface of the spray nozzle.