JPS5813581Y2 - Ion source for mass spectrometers, etc. - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ion source for use in mass spectrometers, etc., which enables ionization by chemical ionization (CI) and ionization by electron impact (EI) in one ionization chamber.

With this kind of ion source, it is necessary to supply and shut off the reaction gas to the ionization chamber in conjunction with switching between CI and EI.

Therefore, conventionally, a valve is provided in the reaction gas introduction pipe connected to the ionization chamber, and the supply of the reaction gas to the ionization chamber is performed by opening and closing the valve.

However, in such a configuration, even if the valve is closed and only the sample gas is supplied into the ionization chamber to perform EI, residual gas remains between the reaction gas introduction tube valve and the ionization chamber. A reactant gas is introduced into the ionization chamber.

Therefore, analysis cannot be performed until the residual reaction gas in the reaction gas introduction tube is completely discharged, and therefore time is wasted between analysis by CI and analysis by EI.

On the other hand, the flow rate of the reaction gas supplied to the ionization chamber during CI analysis is reduced to 0.1 m by providing a needle valve.
Since the flow rate must be set to a minute amount, such as J/min, even if the aforementioned valve is closed and the supply of reaction gas to the ionization chamber is stopped, the valve is opened again and the supply of reaction gas is started. This method has the disadvantage that it takes time to obtain a set stable minute flow rate.

The present invention aims to solve such inconveniences, and will be explained in detail below with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention, in which 1 is a casing of a mass spectrometer, and the inside of the casing is under vacuum (for example,
'Torr).

Reference numeral 2 denotes an ionization chamber installed in the housing 1 via an arbitrary holder (not shown), which is kept at ground potential, and four holes 3 and 4° are provided in the side wall of the ionization chamber. 5.6 are respectively formed.

The inner diameter 3 is relatively thick, for example, 1 to 2 mm in diameter, and the holes 4, 5, and 6 have a diameter or elongated hole width of 30 mm, for example.
It is formed in a minute size such as 0 to 500 μm.

7 is a sample introduction tube for introducing the sample gas to be analyzed into the ionization chamber 2 through the hole 3, and the sample introduction tube is attached to the ionization chamber 2 in an airtight state;
The other end passes through the wall of the casing 1 and is connected to a sample introduction section (not shown).

Reference numeral 8 denotes a reaction gas introduction tube for introducing the reaction gas into the ionization chamber 2 through the hole 4, and one end (on the ionization chamber side) of the reaction gas introduction tube is formed in a hemispherical shape and is connected to the hole 4 of the ionization chamber 2. It is joined to a conical (or spherical or flat) receiving part 9 formed at the edge.

The other end of the reaction gas introduction pipe movably penetrates the wall of the casing 1 in an airtight manner and is taken out into the atmosphere.

A piston valve 10 is integrally fixed to the tip of the reaction gas introduction pipe taken out into the atmosphere.

The piston valve 10 is movably fitted into a cylinder 11 formed on the outer wall of the housing 1, and the piston valve 10 has one end connected to the reaction gas introduction pipe 8 and the other end connected to the outer peripheral surface. A communication hole 12 is formed that reaches the piston valve 10, and two O-ring backings 13a and 13b are arranged on the outer periphery of the piston valve 10 so as to sandwich the communication hole 12 therebetween.

Reference numeral 14 denotes a push rod for moving the reaction gas introduction pipe 8 and the piston valve 10, and a heir 15 is provided at the tip.

16 is a reaction gas introduction port formed in the cylinder 11, and the introduction port 16 is connected to the communication hole 12 of the piston valve 10 when the reaction gas introduction pipe 8 is connected to the receiving part 9 of the ionization chamber 2. It is formed in a position where it can be done.

Further, a pipe 17 communicating with a gas cylinder (not shown) is connected to the inlet 16.

The pipe 17 is provided with a needle valve 18 for adjusting the flow rate of the reaction gas.

19 is a filament, which is connected to the hole 5 provided in the ionization chamber 2.
A heating power source 20 is connected to both ends of the filament.

Furthermore, a negative voltage is applied to the filament 19 with respect to the ionization chamber 2 by a power source 21 or 22.

23 is a changeover switch for changing over this applied voltage.

Reference numeral 24 denotes a control section for controlling switching of the changeover switch 23, and position signals from microswitches 25 and 26 are supplied to the *I leg.

2γ is an exhaust pipe for constantly evacuating the chamber 28 formed by inserting the piston valve 10 into the cylinder 11, and is connected to, for example, an oil rotary pump not shown.

However, when a sample gas is to be ionized by chemical ionization, first the reaction gas introduction tube 8 is joined to the receiving part 9 of the ionization chamber 2, as shown in the figure.

As a result, the communication hole 12 of the piston valve 10 and the cylinder 1
Since the inlet port 16 of No. 1 coincides with the inlet port 16 of No. 1, a predetermined amount of water (0.1 mJ/min.
) is introduced into the ionization chamber 2 and mixed with the sample gas from the sample gas introduction tube 7 and the hole 3.

On the other hand, since the eldest child 15 contacts the microswitch 25 at the same time as the reaction gas introduction pipe 8 joins the ionization chamber 2,
A position signal is sent from the microswitch 25 to the control unit 24, and the changeover switch 23 is connected to the power supply 2 as shown by the solid line in the figure.
Connected to side 1.

As a result, a negative voltage reaching CI with respect to the ionization chamber 2 is applied to the filament 19, so that the electron beam from the filament 19 accelerated by the voltage passes through the hole 5 and is irradiated into the ionization chamber 2. Ru.

As a result, the reaction gas is ionized in the ionization chamber 2, and these ions further ionize the sample gas by chemical ionization, and the resulting sample ions enter a mass spectrometry field (not shown) through the hole 6, where the mass is Separated according to charge-to-charge ratio.

At this time, since the holes 5 and 6 in the ionization chamber 2 have minute diameters, the inside of the ionization chamber is maintained at a relatively high pressure of, for example, several Torr.

Next, when the sample gas is to be ionized by electron bombardment, first move the heir 15 in the direction of arrow A in FIG. 1, and move it to the position shown by dotted line B. Remove the introduction tube 8 from the receiving part 9 of the ionization chamber 2.

As a result, only the sample gas from holes 3 is introduced into the ionization chamber 2, the sample gas is ionized by the electron beam from the filament 19, and is sent through the holes 6 to the mass spectrometry field.

At this time, since the eldest child 15 comes into contact with the microswitch 26, the control section 24 connects the changeover switch 23 to the power supply 22 side, and applies a negative voltage suitable for EI to the filament 19 with respect to the ionization chamber 2.

Furthermore, when the reaction gas introduction pipe 8 is removed from the ionization chamber 2, the communication hole 12 of the piston valve 10 and the introduction port 16 of the cylinder 11 are also disconnected, and the introduction port 16 is communicated with the chamber 28 inside the cylinder 11. , the reaction gas from the pipe 17 is exhausted through the exhaust pipe 27.

Furthermore, since the communication hole 12 of the piston valve 10 is isolated from the chamber 28 by the O-ring backing 13a, the reaction gas is not supplied into the housing 1.

Furthermore, the reaction gas introduction pipe 8 and the piston valve 10 are removed until the reaction gas introduction pipe 8 is completely removed from the ionization chamber 2.
The reaction gas remaining in the communication hole 12 is immediately diffused into the housing 1 and hardly enters into the ionization chamber 2.

As described above, in the present invention, the reaction gas introduction tube is separated from the ionization chamber during EI, so that the reaction gas remains in the reaction gas introduction tube unlike in conventional devices where the supply of reaction gas is stopped by opening and closing a valve. It is possible to prevent the disadvantage that the reactive gas introduced into the ionization chamber can be prevented.

Furthermore, since the reactant gas that has passed through the needle valve when the reactant gas introduction tube is separated from the ionization chamber is exhausted by an oil rotary pump, etc., the reactant gas is always maintained at a set minute flow rate.

Therefore, it is possible to quickly switch from analysis using CI to analysis using EI, or from analysis using EI to analysis using CI.

As a result, when the ion source of the present invention is coupled to gas chromatography, it becomes possible to quickly switch between analysis by CI and analysis by EI for each separated sample component peak. This has great practical effects, such as the ability to easily perform comparisons through analysis.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining the operation of the present invention. 1... Housing, 2...-Ionization chamber, 3, 4.5 and 6
... Hole, 7 ... Sample gas introduction pipe, 8 ... Reaction gas introduction pipe, 9 ... Receiving part, 10 ... Piston valve, 11.
・Cylinder 12...Communication hole, 13a and 13b・
...O-ring backing, 14...Push rod, 15...
legitimate child, 16...inlet, 17...pipe, 18...
・Needle valve, 19...Filament, 20...
・Heating power source, 21 and 22... Power source, 23... Selector switch, 24... Crochet leg, 25... Hi 26...
Microswitch.

Claims (1)

[Scope of utility model registration request] An ionization chamber placed in a vacuum-maintained housing, an introduction tube for introducing a sample gas into the ionization chamber, an introduction tube for introducing a reaction gas into the ionization chamber, and a sample gas introduced into the ionization chamber. or a means for generating electrons for ionizing the reaction gas, the reaction gas introduction tube can be separated from and joined to the ionization chamber, and when the reaction gas introduction tube is separated from the ionization chamber, the reaction gas An ion source for mass spectrometers, etc., which is equipped with a button in the middle of the introduction tube to exhaust the reaction gas with a vacuum pump without supplying it into the housing.