JPH0726695Y2 - Electron capture detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to the structure of an electron capture type detector which is one type of detector for a gas chromatograph.

[Conventional technology]

Electron-capture detectors used as detectors for gas chromatographs are detectors suitable for the analysis of halogen compounds and nitro compounds, and can be used to measure organic mercury, pesticides, PCB residues, and steroids and amino acids. Used for microanalysis as an electronic derivative.

Conventionally, as shown in FIG. 2, the effluent from the column 23 flows upward through a nozzle 24 in a small-volume ionization container 22 in which a source 21 of a radioactive isotope such as ⁶³ Ni is enclosed as a cathode side. It will be sent. Pure nitrogen gas is sent to the surface of the radiation source 21 from another purge gas inflow passage 25, and electrons are formed outside the nozzle 24 by the nitrogen gas and beta rays from the radiation source 21. Electrons are attracted to the upper collector electrode 26 (anode) and collide with the effluent from the column at the outlet of the nozzle 24 to form negative ions when there is an electron affinity substance in the effluent of the column. Negative ions are the collector electrode in the electric field
It is attracted toward 26, but the electrostatic field is weakened by the movement of negative ions. In this case, if a change in power for keeping the current flowing through the collector electrode 26 constant is recorded, a signal proportional to the negative ion concentration can be obtained.

FIG. 3 shows a structure in which the column effluent directly contacts the radiation source 21.

[Problems to be solved by the invention]

A common weak point of the conventional electron capture type detectors is that, when used for a long period of time, the components to be analyzed adhere to the surface of the source or collector electrode, which is a component, and the detection sensitivity gradually decreases. In addition, since radioactive isotopes such as ⁶³ Ni are used as a radiation source, there are legal regulations, and it is not practical to take out internal parts and wash them because the user or the out-of-office facility requires special equipment. It is possible. Therefore, cleaning etc. cannot be done on site and must be sent back to the manufacturer, which is very troublesome. Since the parts of the radiation source, the collector electrode, and the like are made of stainless steel, the phenomenon of accumulation and adhesion of organic substances as sample components cannot be avoided even if the metal temperature is kept high.

This invention was made in view of such problems,
The purpose is to keep the collector electrode clean and to allow replacement work to be performed safely.

[Means for solving problems]

That is, in order to solve the above problems, the present invention mounts a radioisotope around the cell inner space inside the cell body, and inserts a column end portion into the lower part of the cell inner space for inflowing a separated sample. , In the electron trap type detector in which the collector electrode for electron capture is inserted and arranged in the upper part of the inner space of the cell so that the tip of the collector electrode is located in the central part of the radioisotope, And the collector electrode is formed so as to penetrate the cell upper space so that the tip of the collector electrode reaches the center of the radioisotope in the cell inner space, and the collector electrode of the cell upper space is formed. A purge gas inflow passage is provided on the upper end side, and a purge gas discharge passage is provided on the lower end side of the cell upper space.

[Action]

By making the collector electrode considerably longer, the upper temperature of the collector electrode can be kept low. Therefore, it is possible to use a rubber seal material as the seal ring, instead of a metal seal. Furthermore, when the electrode is removed,
^The exposure dose to ⁶³ Ni is also small, so replacement is easy.

By providing a passage for the purge gas inflow and a passage for the discharge gas in the upper space of the cell, the volume around the collector electrode is apparently eliminated, so that the influence at the time of detecting the component is reduced. That is, if the components are not purged, the components will diffuse, but this can be prevented. Further, since the component concentration on the surface of the collector electrode is diluted by the purge gas, the collector electrode surface is less contaminated.

〔Example〕

Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of the inside of the cell of the electron trap detector according to the present invention. In this figure, reference numeral 1 is a cell body, a space 10 is formed inside for installing a radiation source 2 of ⁶³ Ni which is a radioisotope, and an end portion of a column 3 is inserted in the lower portion. Reference numeral 4 denotes a collector electrode fitted and inserted from the upper side of the cell body 1 so that the tip end portion thereof is located at the central portion of the cell body inner space 10. Further, a cell upper space 31 communicating with the cell internal space 10 is extended above the cell main body 1, and a purge gas inflow passage 11 is provided near the upper end of the cell upper space 31 and a lower end of the cell upper space 31. A purge gas inflow passage 12 is provided in the vicinity. As shown in this figure, the length L from the upper end of the cell upper space 31 to the end slightly above the inner space 10 of the cell body is about 50 mm to 100 mm. Therefore, the collector electrode 4 is made considerably longer than the conventional one.

Reference numeral 5 is an O-ring for sealing between the collector electrode 4 and the inside of the cell body 1.
It is sealed with a ring 5 and tightened and fixed to the cell body with a nut 6, and the column 3 is sealed with a ferrule 7 and a nut 8
It is fastened and fixed to the cell body 1 with.

Although the structure of the cell of the electron trap detector according to the present invention is constructed as described above, the upper temperature of the collector electrode 4 can be kept low by making the collector electrode 4 considerably long. Therefore, the O-ring 5 can use a rubber-like sealing material such as silicon rubber.
Conventionally, since the distance between the collector electrodes is short, a metal sealing that can withstand high temperatures, for example, a silver packing, is used, which is expensive. Further, if the collector electrode is short, when the collector electrode 4 is removed, the exposure dose for ⁶³ Ni is also large, and it was legally difficult to open it. However, such a problem can be solved by making the collector electrode 4 considerably long. Further, by providing the passage 11 for the purge gas inflow and the passage 12 for the discharge in the upper part of the cell main body 1, the volume around the collector electrode 4 is apparently eliminated, so that the influence at the time of detecting the component is eliminated. That is, if the components are not purged, the components will diffuse, but this can be prevented. Moreover, since the component concentration on the surface of the collector electrode 4 is diluted by the purge gas, the surface of the collector electrode 4 is less contaminated. However, in this case, the sensitivity decreases, so it is necessary to select an appropriate flow rate.

[Advantage of the Invention] Since the electron capture type detector according to the present invention has the above-described configuration, the collector electrode is less likely to be contaminated. Further, the temperature of the upper part of the collector electrode can be suppressed to a low level, an expensive metal sealing material is not required, and the surface of the collector electrode can be easily inspected and replaced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of the inside of a cell of an electron trap type detector according to the present invention, and FIGS. 2 and 3 are vertical sectional views of the inside of a cell of a conventional electron trap type detector. 1 ... Cell body, 2 ... Radiation source, 3 ... Column, 4 ... Collector electrode, 5 ... O-ring, 6 ... Nut, 7 ... Ferrule, 8 ... Nut, 10 ... Cell internal space, 11 ... Purge gas inflow passage 12 ...... Purge gas exhaust passage

Claims (1)

[Scope of utility model registration request] 1. A cell internal space (10) inside a cell body (1).
A radioisotope (2) is attached to the periphery, a column (3) end for inserting a separated sample is inserted into the lower part of the cell inner space, and an electron trap collector electrode (4) is inserted in the upper part of the cell inner space. In an electron-capture detector in which the tip portion is inserted and arranged so as to be located at the center of the radioisotope, a cell upper space (31) is extended above the cell inner space, and the collector electrode is Through the cell upper space so that the tip of the collector electrode reaches the center of the radioisotope in the inner space of the cell, and a purge gas inflow passageway (11) is formed at the upper end side of the collector electrode in the cell upper space. An electron capture type detector characterized in that a purge gas discharge passage (12) is provided at the lower end side of the cell upper space.