JPH0625752B2 - Gas chromatograph detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a detector for detecting a separated gas in a gas chromatographic analysis.

(B) Conventional technology As a detector for amine compounds and ammonia in gas chromatographic analysis, a thermal ionization detector, a fluorescence detector by a post-column method, a detector by a colorimetric method, etc. have been conventionally used. Both had problems in terms of selectivity and sensitivity.

On the other hand, the applicant of the present application, in Japanese Patent Application No. 60-9956, detects ionization formed when an amine compound and ammonia are brought into contact with the surface of a metal oxide having a large work function. Vessel (Surface ioniz
ation detector, hereinafter referred to as SID).

(C) Problems to be solved by the invention This SID is a detector having a sensitivity of ppb order with respect to amine compounds and ammonia and excellent in selectivity and reproducibility, but other organic compounds Is difficult to detect.

The present invention has been made by further studying in view of such circumstances, and has a function as an SID and a hydrogen flame ionization detector which is often used as a standard high-sensitivity detector for organic components ( Flame ionization detec
tor, hereinafter referred to as FID),
Moreover, the present invention provides a detection device whose switching and use is easy.

(D) Means for Solving the Problems The gas chromatograph detection device of the present invention has at least a part of the surface of which metal is platinum, molybdenum, rhenium or iridium, or an oxide of these metals, or these metal oxides. A heating electrode composed of a combination of a metal and an oxide, a heating power source for supplying power to the heating electrode, a nozzle installed to face the heating electrode, and a sample gas channel connected to the nozzle, A plurality of carrier gas flow paths switchably connected to the nozzle, a collector electrode installed in the vicinity of the heating electrode, a counter electrode installed facing the collector electrode, and a collector electrode opposed to the collector electrode. A DC power source connected to the electrodes via an ammeter (electrometer) so that the polarity can be inverted.

(E) Operation First, on the heating electrode heated by the power supply of the heating power source,
The sample gas supplied from the sample gas channel is blown into contact with air or oxygen supplied by switching selection of the carrier gas channel through a nozzle. At this time, when the polarity of the DC power supply is selected and the positive electrode is connected to the collector electrode and the negative electrode is connected to the counter electrode, the sample gas (amine compound and ammonia) contacts the surface of the heating electrode and is thermally decomposed. , Ionize. The electron flow emitted during this ionization is captured by the collector electrode, amplified by the electrometer, and detected by the recorder or the data processing device. In this way, this detection device acts as an SID.

Next, in the above, the carrier gas flow path was switched to the hydrogen gas flow path, and the hydrogen gas was sprayed to the heating electrode together with the sample gas through the nozzle, and the hydrogen gas was automatically ignited by the high temperature heating electrode, and the nozzle tip A flame is generated, and the flame burns the sample gas to produce io. At this time, if the polarity of the DC power supply is selected and the negative electrode is connected to the collector electrode and the positive electrode is connected to the counter electrode, an ionic current flows between the electrodes and is amplified by the electrometer and detected by the recorder or data processor. To be done. In this way, the detection device also acts as an FID.

(F) Embodiment Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. The present invention is not limited to this.

In the detection device (1) shown in Fig. 1, the outlet of the separation column
(2) is a quartz nozzle through the T-joint (3)
The other pipe (5), which is connected to (4) and is connected to the T-joint (3), is branched and the stop valves (5a), (5
It is connected via b) to a source of oxygen or air and a source of hydrogen (both not shown). Nozzle (4)
The open end (6) of the is open to the ionization chamber (7), and the open end (6)
The nozzle electrode (8) provided on the periphery of the
It is connected to the DC power supply (9) via (19). DC power supply
The output voltage of (9) is usually about 200-300V.

In the ionization chamber (7), an oxygen or air supply port (10) is provided around the nozzle (4). This oxygen or air is for keeping the inside of the ionization chamber (7) in an oxidizing atmosphere, and it is preferable to provide a diffusion plate or the like at the supply port (10) so as to be uniformly dispersed.

A collector electrode (11) is provided in the ionization chamber (7) so as to face the nozzle electrode (8). The collector electrode (11) is formed by integrally forming a cylindrical inner collector electrode (12) and an outer collector electrode (13) via an electrically insulating cylinder (14) made of ceramics. The cylindrical outer collector electrode (13) is the inner collector electrode
It is formed so as to protrude from the end of (12) and surround the periphery of the electrode (15). A platinum wire with platinum oxide formed on the surface is used as the electrode (15).
It may be an oxide film formed when (15) is heated before measurement. The electrode (15) has one end connected to the end of the inner collector electrode (12) and the other end connected to the end of the outer collector electrode (13), and further connected via a transformer (16) to a power controller (17). ) And is designed to be heated to an arbitrary temperature. The electrode (15) is the nozzle electrode (8).
Is fixed at a position, for example, about 6 mm. One of the input terminals of the electrometer (ammeter) (18) is connected to one end of the secondary side of the transformer (16), that is, the inner collector electrode (12), and the other is connected to the polarity reversing switch (19).

In such a configuration, first, the detection device (1) is connected to the SID.
The case of using as will be described.

The sample gas (amine compound and ammonia) flowing out from the separation column outlet (2) is mixed with the air introduced from the pipe (5) at the T-joint (3) when the stop valve (5a) is opened. . In this case, the air flow rate is 10-60ml /
Minutes are preferred.

The sample gas mixed with air flows into the ionization chamber (7) from the tip of the nozzle (4). The sample gas flowing into the ionization chamber (7) is supplied with air (20 to 100 ml /) from the supply port (10).
Min.) And contact with the heated electrode (15) for thermal decomposition, ionizing the amine compound and ammonia,
Generate positive ions. At this time, the polarity reversing switch (19)
Thus, when the negative electrode of the DC power supply (9) is applied to the nozzle electrode (8), the collector electrode (11) becomes the positive electrode, so that the electron flow emitted when positive ions are generated is collected by the collector electrode (11). )
Will catch you. This electron flow is detected and amplified by an electrometer (18) and recorded by a recorder (not shown) or the like.

Next, a case where the detection device (1) is used as an FID will be described.

The sample gas flowing out from the separation column outlet (2) is mixed with hydrogen introduced from the pipe (5) at the T-joint (3) when the stop valve (5b) is opened. In this case, the flow rate of hydrogen is preferably 40-60 ml / min.

The sample gas mixed with hydrogen flows into the ionization chamber (7) from the tip of the nozzle (4). The sample gas flowing into the ionization chamber (7) is mixed with the air supplied from the supply port (10), comes into contact with the heated electrode (15), and is automatically ignited.
Combustion at the open end (6) of (4) produces a hydrogen flame.

At this time, by using the polarity reversing switch (19), the nozzle electrode
When the positive electrode of the DC power supply (9) is applied to (8), the collector electrode
(11) becomes a negative electrode. The organic components burned by the hydrogen flame generate positive ions centering on carbon, which ions are trapped by the collector electrode (11) and detected by the electrometer (18). In this case, the platinum part of the electrode (15) acts as a heating catalyst.

In this way, the detection device (1) can have both SID and FID functions, and the switching operation can be easily performed.

(G) Effect of the Invention According to the present invention, a surface ionization detector (SID) for measuring amine compounds and ammonia with high selectivity and high sensitivity.
And a detector for a gas chromatograph having a function of a hydrogen flame ionization detector (FID) for generally measuring organic compounds.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention. (1) …… Detector, (2) …… Separation column outlet, (4) …… Nozzle, (8) …… Nozzle electrode, (11) …… Collector electrode, (15) …… Electrode, (17) ...... Power controller, (18) …… Electrometer.

Claims (1)

[Claims] 1. A heating electrode comprising platinum, molybdenum, rhenium or iridium, at least a part of which has a metallic surface, or an oxide of these metals, or a combination of these metals and oxides. A heating power supply for supplying power to the heating electrode, a nozzle installed facing the heating electrode, a sample gas flow path connected to this nozzle, and a plurality of carrier gas streams switchably connected to the nozzle. A channel and a collector electrode disposed near the heating electrode,
A detector for a gas chromatograph, comprising: a counter electrode installed to face the collector electrode, and a direct current power source connected to the collector electrode and the counter electrode so that the polarities can be reversed via an ammeter. .