JP2596343B2 - Mass spectrometry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometry, and more particularly to a mass spectrometry suitable for extracting and analyzing ions in an effluent from a separation column.

[0002]

2. Description of the Related Art When a liquid containing ions is caused to flow out of a thin tube to which a high voltage is applied, the liquid becomes conical and charged droplets are ejected from the tip thereof with good directivity. The phenomenon in which ions in a liquid are extracted from the liquid as a droplet by an electric field and sprayed is called EHD (Electrohydrodynamic I
onization). According to this, since it is not necessary to heat the liquid during spraying, even thermally unstable substances known as polar molecules such as amino acids constituting proteins and nucleic acids constituting genes cause thermal decomposition. Nothing.

In the case of this technique, it is possible to spray a liquid of about several μl / min. However, the maximum allowable flow rate is too small to adopt this technique as an ion extraction device for performing mass spectrometry of ions in an effluent coming out of a separation column of a liquid chromatograph. Therefore, semi-micro columns (~ 100ml / min) and packed columns (100μ /
1 / min ~), the effluent is reduced to 1/100 or 1/1.
000 must be split. However, such a split is not easy and significantly detracts from the overall sensitivity of the system.

[0004] Improvements to the above EHD ionization have been proposed. It is Analytical Chemistry, No. 59
Volume 22, November 15, 1987, 2642-26
Page 46 (Analytical Chemistry, Vol. 59, No. 22,
November 15, 1987, pp 2642 to 2646).

According to this, a fused quartz capillary having an inner diameter of 50 μm is inserted into a stainless steel capillary having an inner diameter of 0.2 mm. This is further inserted into a Teflon tube having an inner diameter of 0.8 mm. Dry nitrogen of 2.5 atm and 216 m / sec is flowed between the stainless steel capillary and the Teflon tube. 3 for stainless steel capillaries
A voltage of 600 V is applied to KV and an electrode facing the KV. This allows several tens of μm to be added to the fused silica capillary.
It has been reported that when a liquid of 1 / min flows, a fog of fine particles such as smoke is generated from the capillary.

[0006]

In this technique, it is considered that the nitrogen gas contributes to the stabilization of the liquid cone and the miniaturization of the droplet by the collision with the droplet, which is the main cause of the increase in the flow rate. It is thought that it has become.

However, according to experiments, even with this technique, a liquid having a flow rate of 100 μl / min or more is stably sprayed,
It was difficult to extract ions. For this reason, this technique is still insufficient for backed columns (100 μl / min or more) which are most frequently used in liquid chromatography.

[0008] It is an object of the present invention to provide an ion extraction and analysis apparatus capable of effectively extracting ions.

[0009]

According to the present invention, there is provided an ion extraction apparatus comprising: an electrode; means for guiding a liquid containing ions to the surface of the electrode; and a gas for moving the liquid so as to be sandwiched between the electrode and the electrode. And a means for generating an electric field for extracting the ions.

The ion analyzer according to the present invention comprises: an electrode to which a liquid containing ions is guided on its surface; a means for supplying a gas so as to move the liquid between the electrodes; Means for generating an electric field so as to be extracted and means for detecting the extracted ions are provided.

[0011]

The liquid containing ions guided to the electrode surface is moved by the gas in such a manner as to be sandwiched between the gas and the electrode, and the ions in the space are converted into small droplets by the electric field for ion extraction. And is extracted from the microdroplets by breaking through the liquid surface layer.

Since the liquid is moved by the gas so as to be sandwiched between the gas and the electrode, vaporization by the liquid gas is promoted. In addition, since the moving speed of the surface in contact with the gas of the liquid is higher than the moving speed of the surface in contact with the electrode, the liquid is sprayed on the surface of the liquid in contact with the gas, and the generation of droplets is performed. Promoted.

As described above, the extraction of ions can be effectively performed by promoting the vaporization of the liquid by the gas and by promoting the droplets and droplets of the liquid due to the difference in the moving speed between the two surfaces of the liquid.

When a voltage is applied to the electrodes for forming an electric field for ion extraction, ions of the same polarity as the electrodes, that is, ions to be extracted, are brought into contact with the electrodes on the liquid surface layer in contact with the gas. Opposite charges tend to collect on the liquid surface layer. For this reason, a large amount of ions are contained in the generated droplet, and vaporization of ions, that is, extraction of ions, is further promoted in tandem with Coulomb repulsion between ions.

[0015]

Referring to FIG. 1, an eluent stored in an eluent storage tank 1 is sent to a separation column 5 through a damper 3 and a sample inlet 4 by a pump 2. The damper 3 is used for suppressing the pulsating flow of the eluent by the pump 2.

The sample is added to or injected into the column 5 from the sample inlet 4 and is separated in the course of being sent through the column 5 with an eluent. The effluent from the column 5 is sent to the ion extraction device 6 '.

The nozzle portion 6 of the ion extraction device 6 'is attached to the device wall 6b by a nut 6a, the details of which are shown in FIGS. 2 (a), 2 (b) and 2 (c). Referring to the figure, a linear or needle-like electrode 16 is
And 18 and the nut 17a
7 is attached via an airtight seal 17b. The needle electrode 16 is desirably made of a stable material such as Pt, Au, or C to prevent electrolysis. Needle electrode 16
An insulating knob 15 is attached to one end, and the other end is pointed. Around the needle electrode 16 is disposed a first tube 19, which is attached to the tees 17 and 18 by nuts 17c and 18a via hermetic seals 17d and 18b. Around the first tube 19 is a second
The second tube is attached to the tee 18 by a nut 18c via a hermetic seal 18d. A tube 17e, which communicates with a gap between the needle-shaped electrode 16 and the first tube 19, is attached to the tee 17 via a hermetic seal 17g by a nut 17f.
Is connected to the lower end. The tee 18 has a nut 18 connected to a gap between the first pipe 19 and the second pipe 20.
f through the hermetic seal 18g
8e is connected to the gas source 30. A high voltage is applied to the needle electrode 16 by the power supply 7.
The distal end of the linear electrode 16 protrudes from the distal end surfaces of the first and second tubes 19 and 20, and the amount of protrusion (length)
Can be adjusted by loosening the nut 17a and moving the needle electrode 16 forward and backward.

The effluent from the column 5 sent to the ion extraction device 6 'passes through the pipe 17e and is connected to the needle electrode 16 and the first electrode.
Is led to the gap between the tube 19. The effluent is the needle electrode 1
After passing through 6 and the gap between the first tube 19, the tube 18e from the gas supply apparatus 30, first and second tubular 19 and 2
While being exposed under the contact with the sample feed gas supplied through the gap between zeros, the sample feed gas is fed into the tip of the needle electrode 16 by the sample feed gas. The gas supply device 30 can adjust the gas supply amount. As the sample feed gas, an inert gas such as argon or neon, or a gas such as nitrogen or oxygen can be used.

A high voltage is applied to the needle electrode 16 from the power supply 7, thereby extracting ions from the former to the latter between the needle electrode 16 and the first ion extraction electrode 8 at the ground potential. An electric field for the operation is formed. Therefore, if the effluent contains ions, the feed force of the sample feed gas and the electrostatic force between the needle electrode 16 and the first ion extraction electrode 8 combine to cause ions in the effluent to become needle-like electrodes 16. From the tip of the droplet, it jumps out as a microdroplet due to the liquid surface tension at the tip, and ions are further extracted from the droplet surface. The ions thus extracted pass through the small hole of the first extraction electrode 8 and further pass through the small hole of the second ion extraction electrode 9 at the ground potential. The ions passing through the small holes of the second ion extraction electrode 9 are further extracted by the ion extraction electrode 10 to the quadrupole mass separator 11, which selects only ions having a desired mass number. , The selected ions are detected by detector 12. The mass separator 11 can also sequentially select ions of various mass numbers by mass number sweep. The ions thus selected one after another are successively detected by the detector 12. The detection output signal of the detector 12 is amplified by the amplifier 13 and guided to the data processing device 14. Note that the mass separator 11 may be of a magnet type.

The space between the needle electrode 16 and the first extraction electrode 8 is ventilated using a fan (not shown) to discharge gas remaining in this space. The extraction electrode 10, the mass separator 11, and the detector 12 are arranged in a space evacuated to a predetermined degree of vacuum by a vacuum pump (not shown). The space between the first and second ion extraction electrodes 9 and 10 is also evacuated to a predetermined degree of vacuum by a vacuum pump (not shown).

As described above, the effluent passes through the gap between the needle electrode 16 and the first tube 19 and is then exposed to the sample feed gas while being fed to the tip of the needle electrode 16. It is. Therefore, evaporation of the solvent component in the effluent is promoted, and the ion concentration is increased. When the effluent is forcibly sent to the tip of the needle electrode 16 by the sample feed gas after passing through the gap between the needle electrode 16 and the first tube 19 , the effluent has a liquid surface side flow velocity v2. Needle electrode surface side flow velocity v3
Will be slow. This is because there is friction between the effluent and the surface of the needle electrode 16.

As shown in FIGS. 3 and 4, v
If 1> v2, vaporization and dropletization of the liquid on the liquid surface are promoted, and a droplet is generated. At this time, ions having the same properties as those of the needle electrode 16 are collected on the surface layer of the effluent, and opposite charges are collected near the surface of the needle electrode 16. Therefore, the droplet contains a large amount of ions, and the vaporization of the ions is promoted in combination with the Coulomb repulsion between the ions. Of course, the charge opposite to that of the electrode gathering near the surface of the needle electrode 16 is lost on the surface of the electrode. In FIG. 4, v1 is the flow rate of the sample feed gas.

Thus, even if a relatively large amount of effluent is introduced into the ion extraction device 6 ', its ionization can be performed effectively and stably.

FIG. 5 is a diagram showing the relationship between the amount of effluent flowing into the sample ionizer 6 'and the ion current value. The conditions for obtaining this data are as follows. The diameter of the needle electrode 16 was 100 μm (0.1 mm), and the tip was sharpened by electrolytic polishing so that the radius became about several μm. Dry nitrogen gas was used as the sample feed gas, and the flow rate was set to 1 l / min. As shown in FIG. 2C, the protrusion of the tip of the needle electrode 16 is 5 mm, and the outer diameter and inner diameter of the first tube 19 are 1 mm and 0.25 mm, respectively.
The outer and inner diameters of the second tube 20 were 4 mm and 2 mm, respectively. The voltage applied to the needle electrode 16 is +3 KV
Met.

FIG. 5A shows data when the needle electrode 16 is present, and FIG. 5B shows data when the needle electrode 16 is not present. From these data, it can be seen that the presence of the needle-shaped electrode 16 enables stable and effective ionization even at a relatively large flow rate. On the other hand, when the needle electrode 16 does not exist, the maximum flow rate is several tens ml. From the above,
It can be seen that the presence of the needle electrode 16 achieves stable and effective ionization even with a relatively large amount of effluent.

FIG. 6 shows an ion current measuring system used in obtaining the data of FIG. A shows the case where the needle electrode is present, and B shows the case where the needle electrode is not present. 8 '
Is an extraction electrode, 12 'is an ion detector, 13' is an amplifier,
Reference numeral 30 denotes an ammeter.

FIG. 7 shows the relationship between the amount (length) of protrusion of the needle electrode 16 from the first tube 19 and the ion current value. This data was obtained using the system of FIG. From this data, it can be seen that when the protrusion amount is zero, there is almost no effect. The same applies when the protrusion amount is too large.

The tip of the needle electrode 16 may be sharply pointed, may be flat as shown in FIGS. 7 and 10, or may be round as shown in FIG. Further, the cross section of the needle-shaped electrode 16, the first tube 19 and the second tube 20 may be circular as shown in FIGS. 8 and 9, or rectangular as shown in FIG. Good.

Some sample liquids allow some heating. Heating increases the vaporization efficiency of the solvent component, and thus can further enhance the effect of ion extraction.
11 and 12 are for this purpose, FIG.
Is such that a nozzle block 6 is entirely surrounded by a heat block 21 and is heated by a cartridge heater 23. FIG. 12 shows a configuration in which the atomized components are vaporized through a hollow heat block 23 built in the cartridge heater 23.

Reference numeral 22 denotes a thermocouple for measuring temperature.

[0031]

According to the present invention, there is provided an ion extraction and analysis apparatus capable of effectively performing ion extraction.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a partial configuration of an ion analyzer according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an ion extraction unit of FIG. 1, a right side view of a needle electrode portion, and an enlarged sectional view of a needle electrode tip.

FIG. 3 is a view showing a further enlarged cross-sectional view of a needle electrode tip portion of FIG. 2;

FIG. 4 is a diagram showing an explanatory diagram of a liquid splash effect.

FIG. 5 is a diagram illustrating a relationship between an effluent amount and an ion current value.

FIG. 6 is a diagram showing a configuration diagram of an ion current measurement system.

FIG. 7 is a diagram illustrating a relationship between an amount of protrusion of a needle electrode and an ion current value.

FIG. 8 is an enlarged sectional view of the tip of a nozzle portion of another embodiment, and a right side view thereof.

FIG. 9 is an enlarged sectional view of the tip of a nozzle portion according to another embodiment, and a right side view thereof.

FIG. 10 is an enlarged sectional view of the tip of a nozzle portion according to another embodiment, and a diagram showing a right side view thereof.

FIG. 11 is a sectional view of one embodiment of a heating device.

FIG. 12 is a cross-sectional view of another embodiment of the heating device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Eluent storage tank, 2 ... Pump, 5 ... Column, 6 ... Nozzle part, 6 '... Ion extraction device, 7 ... Power supply, 11 ... Mass separator, 12 ... Detector, 16 ... Needle electrode, 19 ... No. One tube,
20: second tube, 21: heat block, 22: thermocouple, 23: heater.

Claims (1)

(57) [Claims] A first tube is provided in a second tube, and said first tube is provided in said second tube.
In the first electrode provided in the tube, the axial direction of the first tube
A second electrode is provided at a position away from the first tube ,
The first electrode is more of the second tube than the first tube and the second tube.
Extending toward the electrode of the above, the gas is introduced into the gap between the first tube and the second tube, and the sample separated by the separation column is introduced into the gap between the first tube and the first electrode. to extract ions from the sample, before Symbol ions are moved to the second electrode direction, followed by extraction of the ions in the first chamber, the second lower the ion-pressure than the first chamber Mass spectrometry, wherein the mass spectrometry is conducted through a third chamber to a third chamber having a lower pressure than the second chamber.