JPS6232420B2 - - Google Patents
Info
- Publication number
- JPS6232420B2 JPS6232420B2 JP17764280A JP17764280A JPS6232420B2 JP S6232420 B2 JPS6232420 B2 JP S6232420B2 JP 17764280 A JP17764280 A JP 17764280A JP 17764280 A JP17764280 A JP 17764280A JP S6232420 B2 JPS6232420 B2 JP S6232420B2
- Authority
- JP
- Japan
- Prior art keywords
- collector electrode
- current
- collector
- ecd
- voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000005855 radiation Effects 0.000 claims description 7
- 230000005264 electron capture Effects 0.000 claims description 3
- 239000012159 carrier gas Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical class 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000002285 radioactive effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
- G01N27/66—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber and measuring current or voltage
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Toxicology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Description
【発明の詳細な説明】
本発明はガスクロマトグラフにおける電子捕獲
型検出器に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron capture detector in a gas chromatograph.
電子捕獲型検出器（以後ECDと云う）の動作
原理は次のようなものである。第１図で１は
ECDセルでキヤリヤガス流入口１１及び流出口
１２を有する。キヤリヤガスはクロマトグラフの
カラムから流出したガスで、ECDとしてはN2が
適当である。セル１には電子捕集電極２（以下コ
レクタ電極と云う）が挿入してあり、セル１と電
極２との間には電極が正になるように電圧が印加
される。またセル１内にはキヤリヤガスを電離す
るための放射線源３がセル１と同電位で配置して
ある。放射線源３は放射性同位元素で例えば
63Niのようなものが用いられる。５はコレクタ電
極２が貫通しているセラミツク絶縁体である。キ
ヤリヤガスの分子は放射線源から放射されるα線
或はβ線によつて電離され、電離によつて生じた
電子はコレクタ電極２に集められ、電極２に電流
が流れることになる。こゝでキヤリヤガスにＰ或
はハロゲンのような電子親和性の強い元素が混じ
ていると、キヤリヤガスの電離によつて生じた電
子がこれらの元素の原子に捕獲され、これらの元
素の原子は負イオンとなる。所がこれらの負イオ
ンは電子に比し重く易動度が甚だ小さいからコレ
クタ電極２に到達せず、コレクタ２に流入する電
子電流が減少する。このコレクタ電流の減少によ
つてＰ或はハロゲン等の元素を検出できる。これ
がECDの原理で電子親和性の大なる元素に対し
て選択的に高い感度を有している。 The operating principle of an electron capture detector (hereinafter referred to as ECD) is as follows. In Figure 1, 1 is
The ECD cell has a carrier gas inlet 11 and an outlet 12. The carrier gas is the gas leaving the chromatographic column, and N2 is suitable for ECD. An electron collecting electrode 2 (hereinafter referred to as collector electrode) is inserted into the cell 1, and a voltage is applied between the cell 1 and the electrode 2 so that the electrode becomes positive. Further, a radiation source 3 for ionizing the carrier gas is arranged within the cell 1 at the same potential as the cell 1. The radiation source 3 is a radioactive isotope, e.g.
63 Ni is used. 5 is a ceramic insulator through which the collector electrode 2 passes. The molecules of the carrier gas are ionized by alpha or beta rays emitted from the radiation source, and the electrons generated by the ionization are collected at the collector electrode 2, causing a current to flow through the electrode 2. If the carrier gas contains elements with strong electron affinity such as P or halogens, the electrons generated by the ionization of the carrier gas will be captured by the atoms of these elements, and the atoms of these elements will become negative. It becomes an ion. However, since these negative ions are heavier than electrons and have extremely low mobility, they do not reach the collector electrode 2, and the electron current flowing into the collector 2 is reduced. Elements such as P or halogen can be detected by this decrease in collector current. This is the principle of ECD, which has high sensitivity selectively to elements with high electron affinity.
本発明は上述したようなECDをパルス制御定
電流方式で使用する場合の改良に関する。第２図
はECDをパルス制御定電流方式で使用する場合
の回路図である。Ｉは定電流源、Ａ１は演算増幅
器でコンデンサＣと共に積分回路を構成してい
る。VFCは電圧周波数変換器で増幅器Ａ１の
（負の）出出に比例した周波数のパルス信号を出
す。このパルス信号はパルス幅整形器Ｗで上記パ
ルス信号に同期した一定幅のパルス信号に変換さ
れ、積分回路Ｓで鋸歯状波に変換され、トランジ
スタＱのベースに印加される。トランジスタＱは
パルス信号のパルスのある間漸増するコレクタ電
流がトランスＴの一次側を通して流れECDのコ
レクタ電極２には前記パルス信号のある間正の定
電圧が印加される。ECDのコレクタ電流は演算
増幅器Ａ１の反転端子から流出する方向に流れ
る。他方同反転端子には定電流源から一定電流
が流入している。 The present invention relates to improvements when using the above-mentioned ECD in a pulse-controlled constant current system. FIG. 2 is a circuit diagram when the ECD is used in a pulse control constant current method. I is a constant current source, and A1 is an operational amplifier, which together with a capacitor C constitutes an integrating circuit. VFC is a voltage-frequency converter that produces a pulse signal with a frequency proportional to the (negative) output of amplifier A1. This pulse signal is converted by a pulse width shaper W into a constant width pulse signal synchronized with the above pulse signal, converted into a sawtooth wave by an integrating circuit S, and applied to the base of a transistor Q. In the transistor Q, a collector current that gradually increases while the pulse signal is present flows through the primary side of the transformer T, and a constant positive voltage is applied to the collector electrode 2 of the ECD while the pulse signal is present. The collector current of the ECD flows in the direction of flowing out from the inverting terminal of the operational amplifier A1. On the other hand, a constant current flows into the inverting terminal from a constant current source.
今ECDセル１にキヤリヤガスを流しておき、
回路を動作させると当初演算増幅器Ａ１の出力電
圧は０でありトランスＴの２次側出力電圧は０で
ある。従つてＡ１とＣとよりなる積分回路は定電
流源Ｉから流入する電流を積分する。このためＡ
１の出力が負方向に増大しVFCからパルス信号
が出力され始める。VFCからパルス信号が出力
されるようになるとコレクタ電極２に間欠的に電
圧が印加されるようになる。コレクタ電極に電圧
が印加されると同電極に電子電流が流れる。この
電流の方向は増幅器Ａ１の反転端子から流出する
方向であるからＡ１の出力電圧を０に戻すように
作用する。ECDのコレクタ電極に電圧が印加さ
れている時間割合は増幅器Ａ１の出力電圧が（負
方向に）大になる程増すのでＡ１の出力電圧は或
る所でバランスして一定になる。このときのＡ１
の出力電圧が検出出力のベースラインになる。次
にキヤリヤガスに検出すべき親電子性の元素が混
入すると前述したようにECDのコレクタ電極電
流が減少する。そうすると定電流電源Ｉから増幅
器Ａ１へ流入する電気量の方が大になるのでＡ１
の出力電圧は負方向へ増大した所でバランスす
る。従つて増幅器Ａ１の出力を記録計で記録する
とクロマトグラムが画けることになる。 Now let the carrier gas flow through ECD cell 1,
When the circuit is operated, the output voltage of the operational amplifier A1 is initially 0, and the secondary output voltage of the transformer T is 0. Therefore, the integrating circuit made up of A1 and C integrates the current flowing from the constant current source I. For this reason A
1's output increases in the negative direction, and a pulse signal begins to be output from the VFC. When a pulse signal is output from the VFC, a voltage is intermittently applied to the collector electrode 2. When a voltage is applied to the collector electrode, an electron current flows through the collector electrode. Since the direction of this current is the direction in which it flows out from the inverting terminal of amplifier A1, it acts to return the output voltage of A1 to zero. The proportion of time during which a voltage is applied to the collector electrode of the ECD increases as the output voltage of the amplifier A1 increases (in the negative direction), so the output voltage of A1 becomes balanced and constant at a certain point. A1 at this time
The output voltage of is the baseline of the detection output. Next, when an electrophilic element to be detected is mixed into the carrier gas, the collector electrode current of the ECD decreases as described above. In this case, the amount of electricity flowing from the constant current power supply I to the amplifier A1 becomes larger, so A1
The output voltage of is balanced when it increases in the negative direction. Therefore, if the output of amplifier A1 is recorded with a recorder, a chromatogram will be drawn.
上述したようなパルス制御定電流方式でECD
を用いる場合精密な検討によるとECDのコレク
タ電極２に電圧が印加されていない時でもコレク
タ電極には２〜3nA程度の電流が流れていること
が明かになつた。これは丁度ECDセルが電池の
ような作用を呈しているからである。この電池作
用の機構は明かでないが、放射線源金属とコレク
タ電極との間の接触電位差が原因かとも考えられ
る。このようなコレクタ電極２とセル１間の電圧
が０のときに流れるコレクタ電流は気温、キヤリ
ヤ流量、放射線源の強さコレクタ電極の交換等に
よつて変りまた時間的にも変動するもので、実効
的に定電流源Ｉの出力電流を変化させるのと同じ
になりクロマトグラムのベースラインを不安定に
する。本発明はこゝに述べたコレクタ電極セル間
電圧０のときのコレクタ電流を０にしてベースラ
インの安定化を計ることを目的としてなされた。 ECD using the pulse control constant current method as described above.
When using ECD, a detailed study revealed that even when no voltage is applied to the collector electrode 2 of the ECD, a current of about 2 to 3 nA flows through the collector electrode. This is because the ECD cell behaves like a battery. Although the mechanism of this battery action is not clear, it may be caused by the contact potential difference between the radiation source metal and the collector electrode. The collector current that flows when the voltage between the collector electrode 2 and the cell 1 is 0 changes depending on the temperature, carrier flow rate, strength of the radiation source, replacement of the collector electrode, etc., and also fluctuates over time. This is effectively the same as changing the output current of the constant current source I, making the baseline of the chromatogram unstable. The present invention has been made for the purpose of stabilizing the baseline by reducing the collector current to zero when the voltage between the collector electrode and the cell is zero.
上述したようにECDにおけるコレクタ電極セ
ル間電圧０のときに流れるコレクタ電流の原因は
明かでなくても、この電流が流れるのはコレクタ
電極に電子が入るからである。そこで本発明では
第３図に示すようにコレクタ電極２の表面に絶縁
被膜４を形成した。コレクタ電極セル間電圧が０
の場合コレクタ電極に衝突する電子の運動のエネ
ルギーはきわめて小さいから、上記被膜を貫通し
てコレクタ電極２に侵入しコレクタ電流を与える
と云うことができず、被膜４の表面に付着して以
後の電子の衝突を阻止する。コレクタ表面に付着
して以後の電子の衝突を阻止にするために必要な
電荷量はきわめて微小でありコレクタ電極印加電
圧０時にこの電荷量によつて流れるコレクタ電流
は殆んど完全に無視できるものである。 As described above, although the cause of the collector current that flows when the voltage between the collector electrode and the cell in the ECD is 0 is not clear, the reason why this current flows is that electrons enter the collector electrode. Therefore, in the present invention, an insulating coating 4 is formed on the surface of the collector electrode 2 as shown in FIG. Collector electrode cell voltage is 0
In this case, the kinetic energy of the electrons colliding with the collector electrode is extremely small, so it cannot be said that the electrons penetrate the film and enter the collector electrode 2 to provide a collector current, but instead adhere to the surface of the film 4 and cause subsequent damage. Prevents electron collisions. The amount of charge required to adhere to the collector surface and prevent future electron collisions is extremely small, and the collector current flowing due to this amount of charge when the voltage applied to the collector electrode is 0 can be almost completely ignored. It is.
上述した絶縁被膜は余り厚いとコレクタ電極に
電圧を印加してもコレクタ電流が流れることがで
きない。この厚さを適当にしておくとコレクタ電
極セル間に40〜50Vの電圧をかけることにより、
コレクタ電極に衝突する電子が加速されて絶縁被
膜を貫通してコレクタ電極に侵入できるようにす
ることができる。実験によるとコレクタ電極とし
てステンレス鋼を用い、表面にSiO2の500〜4000
Åの被膜を形成するとコレクタ電極電圧０のとき
コレクタ電流が流れるのを阻止し、コレクタ電極
電圧40〜50Vでは充分にコレクタ電流が流れ得る
ような絶縁被膜となることが判つた。なお絶縁被
膜としてはTiO2でも良い結果が得られる。 If the above-mentioned insulating film is too thick, collector current will not flow even if a voltage is applied to the collector electrode. If this thickness is set appropriately, by applying a voltage of 40 to 50 V between the collector electrode cells,
Electrons impacting the collector electrode can be accelerated to penetrate the insulating coating and enter the collector electrode. According to experiments, using stainless steel as the collector electrode, 500 to 4000 of SiO2 on the surface
It has been found that forming an insulating film with a thickness of .ANG. prevents collector current from flowing when the collector electrode voltage is 0, and allows sufficient collector current to flow when the collector electrode voltage is 40 to 50V. Note that good results can also be obtained with TiO 2 as the insulating film.
本発明ECDは上述したような構成でコレクタ
電極表面に絶縁被膜を形成すると云うきわめて簡
単な方法でECDのコレクタ電極電圧０時のコレ
クタ電流を抑止し得たもので、コレクタ電極電圧
０時のコレクタ電流が０なので、この電流の不安
定性によるクロマトグラムベースラインの不安定
が解消され、かつ被検出元素の濃度が高い場合、
コレクタ電流が少いからコレクタ電極電圧０時の
コレクタ電流の大小の影響を強く受け、測定結果
が不安定で直線性も低下する所を、安定に直線性
良く測定することができるようになつた。 The ECD of the present invention has the above-mentioned configuration and can suppress the collector current when the collector electrode voltage is 0 using an extremely simple method of forming an insulating film on the surface of the collector electrode. Since the current is 0, the instability of the chromatogram baseline due to the instability of this current is eliminated, and if the concentration of the detected element is high,
Because the collector current is small, it is strongly affected by the magnitude of the collector current when the collector electrode voltage is 0, resulting in unstable measurement results and decreased linearity. Now, it is now possible to measure stably and with good linearity. .
第１図は一般的ECDの縦断側面図、第２図は
パルス制御定電流方式でECDを使用する場合の
回路図、第３図は本発明に係るECDのコレクタ
電極の縦断面図である。
１……ECDセル、２……コレクタ電極、３…
…放射線源、４……コレクタ電極表面の絶縁被
膜。
FIG. 1 is a longitudinal sectional side view of a general ECD, FIG. 2 is a circuit diagram when the ECD is used in a pulse-controlled constant current method, and FIG. 3 is a longitudinal sectional view of the collector electrode of the ECD according to the present invention. 1...ECD cell, 2...Collector electrode, 3...
...Radiation source, 4...Insulating coating on the surface of the collector electrode.
Claims (1)
捕集用電極を挿入した構造で上記電子捕集用電極
表面に加速された電子が貫通可能な程度の厚さに
絶縁性被膜を形成したことを特徴とする電子捕獲
型検出器。1 A radiation source is placed in a cell, and an electron collection electrode is inserted into the cell, and an insulating film is formed to a thickness that allows accelerated electrons to penetrate the surface of the electron collection electrode. This is an electron capture detector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17764280A JPS57100346A (en) | 1980-12-15 | 1980-12-15 | Electron capturing type detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17764280A JPS57100346A (en) | 1980-12-15 | 1980-12-15 | Electron capturing type detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57100346A JPS57100346A (en) | 1982-06-22 |
| JPS6232420B2 true JPS6232420B2 (en) | 1987-07-14 |
Family
ID=16034554
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17764280A Granted JPS57100346A (en) | 1980-12-15 | 1980-12-15 | Electron capturing type detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57100346A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015159463A1 (en) * | 2014-04-17 | 2015-10-22 | 株式会社島津製作所 | Electron capture detector |
-
1980
- 1980-12-15 JP JP17764280A patent/JPS57100346A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57100346A (en) | 1982-06-22 |
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