JPS62241250A - Ion source for mass spectrometer - Google Patents

Abstract

PURPOSE:To regularize a flux of a sample liquid led to an ionization chamber by connecting a splitter to a leading-in tube to lead the sample liquid into the ionization chamber, and supplying a gas under fixed pressure into an exhaust flow passage of residual sample liquid taken out of the ionization chamber. CONSTITUTION:A sample liquid is led from a liquid choromatograph 1 into an ionization chamber 2, subjected to an electron bombardment with electrons from a filament 7 to generate a sample ion which is taken out from an exit 11. The sample liquid in a leading-in tube 3 is led through a porous member 4 and the residual sample liquid is exhausted through an exhaust tube 5 by connecting a splitter to the lead-in tube 3. Then, an airpipe 15 is connected to the exhaust tube 5 to supply a gas from a gas cylinder 16 through a regulated pressure valve 17. And the gas under a regulated pressure is mixed into the residual sample liquid. Thus, a stabilized flow of the sample liquid to be led into the ionization chamber can be maintained even when an outgoing flux of the sample liquid fluctuates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion source for a mass spectrometer in which a liquid sample is directly introduced into an ionization chamber and ionized.

[Prior Art] As a method of introducing a sample liquid into the ion source of a mass spectrometer and ionizing it, as described in Utility Application No. 59-202102 and Japanese Patent Application No. 61-2946@, a sample liquid is introduced into an ionization chamber. There is a method in which a porous member is attached to the tip of the introduction tube into which the sample liquid is introduced and ionized in such a way that the sample liquid oozes into the ionization chamber through the porous member.

FIG. 5 is a schematic diagram showing the structure of the sample introduction section of such an ion source. In the figure, 1 is a liquid chromatograph, 2 is an ionization chamber, 3 is an introduction tube that carries the sample liquid from the liquid chromatograph to the ionization chamber, 4 is a porous member attached to its tip, and 5 is a part of the attachment for excess sample. A discharge pipe for splitting the liquid, 6 is a flow rate regulating valve connected to the discharge pipe.

In such an introduction method, the flow rate of the liquid from the liquid chromatograph is about 10 to 100 μ/min, while the flow rate of the sample liquid seeping into the ionization chamber through the porous member is 1 μ/min.
Since the split ratio is about 1:10 to 1:10
It will be about 0.

[Problem to be Solved by the Invention 1] At such a large split ratio, fluctuations in the flow rate in the flow rate adjustment valve 6 or fluctuations in the amount of liquid sent from the liquid chroma 1 graph will cause the flow rate of the sample liquid passing through the porous member to decrease. has a major impact on

For example, a sample liquid sent from the liquid chromatograph 1 at a flow rate of 101 μg/min is sent to the porous member 4 at a flow rate of 1 μg/min.
When the flow rate at the regulating valve 6 fluctuates by about ±0.5% (0°5 μ/min included) due to fluctuations in conditions such as temperature changes, when the flow rate at the regulating valve 6 is split at a rate of 100 μ2/min to the discharge pipe 5, the regulating valve Regarding, the fluctuation is only 0.5%, but
The flow rate of the sample liquid passing through the porous member 4 is 1±0.5゛μ
Q/min, which fluctuates by as much as 50%. This is the same even when the amount of sample ni sent from the liquid chromatograph varies, making stable ionization difficult.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ion source that can stabilize the flow rate of a sample liquid passing through a porous member.

[Means for solving the problem] In order to achieve this object, the present invention includes an ionization chamber, an introduction tube for introducing a sample liquid into the ionization chamber from the outside, and an inlet tube attached to the tip of the introduction tube. In the ion source for a mass spectrometer, the liquid sample is introduced into the ionization chamber 2 through the porous member and is ionized. The present invention is characterized in that gas at a constant pressure is supplied to a channel for discharging excess sample liquid, thereby applying a constant pressure to the channel.

[Function] In the present invention, gas under a constant pressure is supplied to the flow path for discharging excess sample liquid from the splitter, so the pressure in the porous member portion is kept constant even if the flow rate fluctuates. . Therefore, the flow rate of the sample liquid introduced into the ionization chamber through the porous member can be kept constant.

Hereinafter, one embodiment of the present invention will be explained in detail using the drawings.

[Example] Fig. 1 is a schematic diagram showing an example of an embodiment in which the present invention is applied to an electron W-strike type ionization ([I) ion source, and the same components as in Fig. 5 are designated by the same numbers. is attached. In FIG. 1, the electrons generated from the filament 7 are
It enters the ionization chamber 2 from the ionization chamber 2 and reaches the collection electrode 10 via the output II O' 9.

The sample ions generated by this electron bombardment exit 1.
1 and is accelerated and focused by a slit electrode 12. 13 is the introduction pipe 3. An insulated pipe holds the discharge pipe 5 and the porous member 4 together, and 14 is a seal member that seals the tail of the insulated pipe.

Reference numeral 15 denotes an air supply pipe connected to the exhaust pipe 5, which sends gas generated from the gas cylinder 16 into the exhaust pipe 5 via a constant pressure valve 17.

In the above configuration, the sample liquid is sent through the introduction tube 3 at a flow rate of 101 μ/min, as in the previous explanation, and one of the
μC! , 7 minutes to porous member 4, 100 ti Q 7
It is assumed that the amount is split to the discharge pipe 5. on the other hand,
Air at a constant pressure (nitrogen gas or the like may also be used) is supplied to the exhaust pipe 5 via the air supply pipe 16 at a flow rate of, for example, about 10,000/min.
is mixed in, and this air is discharged through the valve 6 together with the excess sample liquid.

When gas at a constant pressure is present in the discharge channel in this manner, the pressure inside the pipe at the position of the porous member 4 is kept constant even if, for example, the delivery flow rate of the liquid chromatograph fluctuates.

That is, in the example of FIG. 5 in which the flow path from the inlet pipe 3 to the discharge pipe 5 and valve 6 is filled with sample liquid, the volume of the sample liquid that can be present in the flow path is determined, and this If there is even a slight fluctuation in the flow rate, that fluctuation will immediately lead to a large fluctuation in the pressure inside the pipe, which will cause the porous member 4 to
The flow rate of the sample liquid passing through the tube also changes significantly.

However, in the present invention, in which a constant pressure gas coexists with the sample liquid in the discharge channel, the volume of the gas easily changes, so the volume (hang) of the sample liquid that can be present in the flow channel is not constant, but varies over a width. There is. Furthermore, since the gas is supplied at a constant pressure, even if there is a fluctuation in the flow as described above, the pressure of the sample liquid at the position of the porous member 4 is always maintained at a constant pressure related to the pressure of the gas. It turns out. Therefore, the flow rate of the sample liquid passing through the porous member 4 can be kept constant.

To adjust the flow rate of the sample liquid passing through the porous member 4,
Needless to say, it is sufficient to adjust the pressure of the sample liquid at the position of the porous member by appropriately adjusting the gas pressure.

The sample liquid introduced into the ionization chamber can be ionized by chemical ionization or -several particle beam impact ionization.

Various ionization methods such as pre-laser ionization can be applied in addition to electron impact ionization.

Furthermore, in the above embodiment, the splitter was provided at the end of the introduction pipe 3, that is, at the porous member 4, but as shown in FIG. It can also be used as a splitter.

Furthermore, the pressure setting range by the constant pressure valve 17 includes atmospheric pressure or lower. When setting the pressure to below atmospheric pressure, as shown in Fig. 3, the discharge pipe after the valve 6 is led to the waste liquid reservoir 18, and the inside of this waste liquid reservoir is depressurized by the vacuum pump 19 to below the pressure set by the constant pressure valve. It is necessary to ensure that the sample liquid and gas are discharged smoothly.

Furthermore, in the above embodiment, constant-pressure gas was mixed into the flow path between the splitter and the flow rate adjustment valve, but essentially, constant-pressure gas was supplied to the sample liquid discharge path from the splitter. It is sufficient if a constant pressure can be applied to the flow path.

For example, as shown in FIG. 4, the υ outlet pipe 16 may be led directly to the drain reservoir 18, and constant pressure gas may be introduced into the drain reservoir 18 via the air supply pipe 15. If a structure is adopted as this drainage reservoir, such as a gas tank, in which the internal pressure is kept constant by the bottom of the lid, the gas cylinder 16 and the constant pressure valve 17 are not necessarily required.

[Effects] As detailed above, according to the present invention, the flow rate of the sample liquid passing through the porous member is stabilized by providing a means for introducing constant pressure gas into the discharge flow path from the splitter. An ion source for a mass spectrometer that can be used is realized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment in which the present invention is applied to an electron impact ionization (Fl) ion source, and FIGS.
The figures are schematic diagrams for explaining other embodiments of the present invention, respectively.
FIG. 5 is a schematic diagram showing the structure of a sample introduction section of an ion source in which sample F1 liquid is introduced and ionized by seeping into the ionization chamber through a porous member. 1: Liquid chromatograph 2: Ionization chamber 3: Inlet pipe 4: Porous member 5: Discharge pipe

Claims (1)

[Claims] An ionization chamber, an introduction tube for introducing a sample liquid into the ionization chamber from the outside, and a porous member attached to the tip of the introduction tube, the liquid sample being introduced into the ionization chamber through the porous member. In an ion source for a mass spectrometer configured to perform ionization, a splitter is connected to the introduction tube, and a gas at a constant pressure is supplied to the flow path for discharging the excess sample liquid taken out from the splitter. An ion source characterized by applying a constant pressure.