JPH09119915A - Equipment for sample ionization and mass spectrometry - Google Patents

Abstract

(57) Abstract: To provide a sample ionizer and a mass spectrometer capable of stable ionization of a sample. SOLUTION: When a sample is atomized by spraying and the atomized sample is ionized, a space in which the sample is sprayed is surrounded, and a gas is forcibly guided to the spray space from the outside.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus for ionization and mass spectrometry of samples.

[0002]

2. Description of the Related Art According to a liquid chromatograph mass spectrometer, an effluent containing a sample component and a solvent flowing out from a liquid chromatograph is guided to an atomizer and atomized. The atomized effluent is further led to a desolvation chamber where the solvent therein is separated and removed from the sample components. The sample component is introduced into the ion source to be ionized, the ions thus generated are introduced into the mass spectrometric section for mass analysis, and the mass analyzed ions are detected. According to a commonly used or known atomizer, the effluent from a liquid chromatograph is jetted into the atmospheric pressure from a pipe with an inner diameter of 100 μm and atomized, and the atomized effluent also has an inner diameter of 100 μm. It is led to a desolvation chamber through a pipe. Related to this is Analytical Chemistry.
Chemistory), 1988, Volume 60, 774-780.
Is mentioned.

[0003]

As described above, in a general atomizer, the effluent is atomized into the atmosphere. Therefore, since the atmosphere is sucked around the spray stream due to the friction between the spray stream and the surrounding atmosphere, collision between the atomized droplets and the gas is activated and the atomization of the droplets is promoted.

However, since the spray space of the effluent is open to the atmosphere, the suction of the outside air is directly affected by the turbulence of the outside air, so that stable ionization is impaired, which leads to a decrease in the accuracy of mass spectrometry. There is.

Therefore, it is an object of the present invention to avoid directly affecting the supply of gas to the spray stream by ambient fluctuations,
An object is to provide an apparatus for ionization and mass spectrometry of a sample suitable for stable ionization.

[0006]

According to the present invention, the sample atomizing means is composed of a member surrounding the space in which the sample is sprayed, a corona electrode for ionizing the atomized sample, and a gas from the outside into the spray space. And means for forcibly guiding.

The space in which the sample is sprayed is surrounded by the space surrounding member, and gas is forcibly supplied to the space from the outside. Therefore, according to the present invention, the influence of the direct atmospheric fluctuation of the gas supply amount to the jet flow is reduced as compared with the commonly used or known example, and thus stable ionization is achieved.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, an eluent storage tank 1 is shown.
The eluent, which is the mobile phase, is stored in the pump 2 and is sent out by the pump 2 to have a pulsating flow in the damper 3 and becomes a stable flow and is sent to the column 5 through the sample inlet 4. A sample is injected from a sample injection port 4 and separated by a column 5 for each component. The eluent is sent to a liquid chromatograph / mass spectrometer (LC / MS) interface 6 '. In the interface 6 ', the micropipe 6 is heated by the heat block 8 having the heater 7 built therein. Eluent is micropipe 6
The spraying chamber 8a of the desolvation chamber 9 is sprayed from the tip of a. The fog droplets generated thereby are used in the desolvation chamber 9 containing the heater 7.
Is vaporized by heating and reaches the corona discharge needle 10 part. A high voltage is supplied to the corona discharge needle 10 from the high voltage power supply 11, and corona discharge is generated from the tip of the corona discharge needle portion. This corona discharge ionizes the solvent molecules in the effluent from the column 5, and further ionizes the solute molecules, that is, the sample components. After the ion molecule reaction, unnecessary solvent is exhausted into the atmosphere through the opening 19 by a fan. The generated ions are the first skimmer 1
After being introduced into the differential evacuation system section 20 via 2, the solvent molecules are exhausted by a vacuum pump. The ions are further guided from the second skimmer 13 to the mass spectrometric section 14 '. That is, the ions are accelerated by the ion extraction electrode 14, enter the quadrupole 15, undergo mass analysis, that is, a mass sieve, and are detected by the detector 16. The output of the detector 16 is amplified by the DC amplifier 17,
It is sent to the data processing device 18. Here, the mass spectrometer is a quadrupole, but may be a magnetic field type or another type.

The desolvation chamber 9 is connected to the heat block 8 via a heat insulator 8b, whereby the micropipe 6 and the desolvation chamber 9 can be heated and set to different temperatures.

The desolvation chamber 9 is provided with a plurality of gas suction ports 9a so as to be arranged at equal intervals around the spray flow from the tip of the micropipe 6, from which the atmosphere is sucked around the spray flow. To be done.

The effluent from the column 5 is a micropipe 6
It is not vaporized inside and is atomized at once when ejected from its tip into the spray chamber 8a (which has a conical shape symmetrical with the spray flow axis). According to Bernoulli's law, this atomized spray flow attracts the atmosphere by friction with the atmosphere from the gas suction port 9a, and the collision of the droplets generated thereby and the sucked gas is activated, resulting in a mist-like liquid. The micronization of the droplets is promoted. This miniaturization leads to an improvement in ionization efficiency, and thus an improvement in sensitivity of mass spectrometry. Of course, the droplets thus miniaturized are further miniaturized by being exposed to heating when passing through the desolvation chamber 9.

As can be seen from the description, the spray chamber 8a is not completely open to the atmosphere but is surrounded by a wall, and therefore the amount of suction of the air, that is, gas supply toward the spray flow, is larger than that of the complete open atmosphere. Volumes are not directly affected by atmospheric changes. For this reason, stable ionization is achieved.

2 and 3 show the essential parts of the interface of another embodiment according to the present invention. The gas introduction hole 9a-1 is provided in the heat block 8. The supplied gas is heated when passing through the heat block 8. The heated gas collides with the droplets and becomes finer to further promote vaporization. A plurality of gas introduction holes 9a-1 may be provided symmetrically with respect to the spray axis so that the gas is stably supplied.

FIG. 4 shows the essential parts of the interface of yet another embodiment according to the present invention. In this embodiment, a slight gap 9a-is provided between the heat block 8 and the desolvation chamber 9.
2 is provided, and gas is supplied to the spray flow through this gap. Reference numeral 9c is an adjusting tool, which is screwed to the outer circumference of the heat block 8 and the outer circumference of the desolvation chamber 9, respectively. However, the screw engagement with one is a left screw engagement, and the screw engagement with the other is a right screw engagement. Therefore, the gap 9a-2 can be adjusted by turning the adjusting tool 9c. Further, the outer periphery of the adjusting tool 9c is largely opened so as not to hinder the flow of gas.

FIG. 5 shows the essential parts of the interface of another embodiment according to the present invention. As in FIG. 4, a gap 9a- through which gas passes between the heat block 8 and the desolvation chamber 9
3 is the same, but in FIG. 5 only the gap 9a-
The spray outflow end of the heat block 8 has a convex conical shape, and the spray inflow end of the desolvation chamber 9 has a concave conical shape with the same inclination so that 3 has a conical annular shape. Compared to FIG. 4, the gas introduction path is inclined, so that the gas introduction becomes more stable.

In both cases of FIG. 4 and FIG. 5, the gap 9a is formed.
The size of -2 and 9a-3 is important.

Experimental data showing the relationship between the distance D and the cluster ions using the heat block and the desolvation chamber having the shapes shown in FIGS. 6 and 5 are shown. The measurement conditions are as follows.

Mobile phase: 100% water Heat block: 320 ° C. Desolvation chamber temperature: 400 ° C. When water is sprayed, {H ₃ O (H ₂ O) _n } appears on the mass spectrum.
⁺ (N = 0 to 10) ions appear. Figure 6 shows {H ₃ O
(H ₂ O) _n} ⁺ a shows the relationship between the ionic strength I ₁ and _{{H 3 O (H 2 O} ) 5} ionic strength I ₂ of ⁺ ions intensity ratio I ₂ / I ₁ and distance D is there. If the distance D is 1 mm or less, {H ₃ O (H
₂ O) ₅ } ⁺ is stronger than {H ₃ O (H ₂ O)}. However, when D becomes 2 mm, this ratio sharply decreases, and when the distance exceeds 2 mm, the ratio increases a little, and when it exceeds 10 mm, it starts to decrease again.

FIG. 7 shows the relationship between the sensitivity (area value) of the pseudo-molecular ion and the interval D when 100 nanograms of pyridine was injected under the same conditions as in FIG.

The maximum sensitivity is shown at 2 mm, and the distance gradually decreases as the distance D increases. The vertical axis is an arbitrary unit.

FIG. 8 shows the relationship between the sensitivity (peak area) and flow rate of the pyridine pseudo-molecular ion (m / z 80) when the distance is 2 mm and 20 mm. The heat block temperature was set so that the maximum sensitivity was obtained at a flow rate of 1 ml / min, and the value was not changed throughout the experiment. The sensitivity of pyridine at 1 ml / min is 1
It is plotted as 00. When the distance D is 20 mm, the sensitivity becomes 50% at 0.5 ml / min and 1.5 ml / m.
In contrast to 0.3 ml / min when the distance D is 2 mm
And 1.6 ml / min, and it can be seen that the usage range of the interval 2 mm has expanded.

Considering the above facts, it is considered that when the distance D is 0, that is, when the heat block and the desolvation chamber are in close contact with each other, a negative pressure is generated in the spray chamber, the atomization of the mist is not performed, and the cluster ions become large. Therefore, the sensitivity of the pyridine ion becomes insufficient. On the other hand, if the distance is made large (20 mm), air is supplied well, and the fog becomes finer, and cluster ions become smaller. However, since air having a relatively low temperature is supplied, there is a limit to finer fog. 2mm spacing
In the above, since the air is heated as it passes through the heated interval, it is considered that the mist becomes finer. for that reason,
It is considered that a decrease in cluster ions and an increase in analyte ions were obtained.

FIG. 9 shows a main part of an interface of still another embodiment according to the present invention. The embodiment up to FIG. 5 is a natural supply type in which the gas supply utilizes the decompression phenomenon due to the spray flow passing through the atomization chamber 8a, whereas the embodiment in FIG. 9 is forcedly supplied to supply the gas. It is of the type that can. That is, when a gas such as nitrogen or helium is stored in the gas reservoir 10 at a pressure of 1 atm or more, the gas is introduced from the gas reservoir 10 into the gas inlet port 9d and the annular gas inlet port 9d.
e and a plurality of gas outlets 9f provided on the circumference are forcibly supplied to the atomization chamber 8a. Of course, if the gas is stored in the gas reservoir 10 so that the pressure of the gas reservoir 10 becomes 1 atm, the gas is atomized in the atomization chamber 8 as in the natural supply system described above.
It is supplied to the atomization chamber 8a according to the reduced pressure state of a. Reference numeral 11 is a heater for heating the gas reservoir 10.

The interface according to the present invention can also be used in SFC / MS (supercritical fluid chromatograph / mass spectrometer), capillary zone electrophoresis / mass spectrometer, and as a detector of a liquid chromatograph. You can also

[0025]

According to the present invention, the gas supply to the spray stream is prevented from being directly affected by fluctuations in the ambient air, and therefore, for ionization and mass spectrometry of a sample suitable for stable ionization. A device is provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an LC / MS showing an embodiment according to the present invention.

FIG. 2 is a longitudinal sectional view of a main part of another interface according to the present invention.

3 is a sectional view taken along the line III-III ′ of FIG.

FIG. 4 is a longitudinal sectional view of a main part of an interface of another embodiment according to the present invention.

FIG. 5 is a longitudinal sectional view of a main part of an interface of another embodiment according to the present invention.

[FIG. 6] Ion intensity ratio I ₂ / I ₁ to gas inflow interval D
FIG.

FIG. 7 is a diagram showing a relationship of an ion intensity I with respect to a gas inflow interval D.

FIG. 8 is a diagram showing a relationship of sensitivity with respect to a sample injection amount.

FIG. 9 is a vertical cross-sectional view of a main part of an interface according to still another embodiment of the present invention.

[Explanation of symbols]

5 ... column, 8 ... heat block, 9 ... desolvation chamber, 9d
... Gas inlet, 14 '... Mass spec, 18a ... Atomization chamber.

Claims (6)

[Claims] 1. A sample ionization device comprising a means for atomizing a sample and a corona discharge electrode for ionizing the atomized sample, wherein the sample atomizing means defines a space in which the sample is sprayed. An ionization device for a sample, comprising: a surrounding member; and means for forcibly introducing a gas into the spray space from the outside. 2. The ionization device according to claim 1, further comprising a gas reservoir for accumulating the gas, wherein the gas is introduced from the gas reservoir to the spray space. 3. The ionization device according to claim 2, wherein nitrogen or helium is stored in the gas reservoir. 4. The ionization device according to claim 2, wherein the pressure of the gas stored in the gas reservoir is 1 atm or less. 5. The ionization device according to claim 2, further comprising a heater for heating the gas. 6. A liquid chromatograph, means for atomizing an effluent containing a sample component and a solvent from the liquid chromatograph, a corona gas electrode for ionizing a sample in the atomized effluent, and the same. A means for mass-separating the ionized ions, and a means for detecting the mass-separated ions, wherein the atomization means defines a space in which the effluent from the liquid chromatograph is sprayed and its spray. And a means for forcibly introducing a gas into the space from the outside.