JPS5940261B2 - thermal ionization detector - Google Patents

Description

[Detailed description of the invention] The present invention relates to thermal ionization detectors.

Traditionally, FTDs (Flame Ionization Detectors) have been preferred for gas chromatographs because they respond with high sensitivity to all organic compounds with a few exceptions.

However, FID cannot be used when it is desired to respond only to a specific substance, such as a phosphorus compound or a nitrogen compound. Therefore, FPD (Flame Photometric Detector) is used for phosphorus compounds and sulfur compounds, and ECD (Electron Capture Detector) is used for halogen compounds.
This problem is solved by using two types of detectors: However, there is currently no detector that responds to nitrogen compounds, and the only solution is to add KB to FID.
Attempts have been made to selectively and highly sensitively analyze nitrogen compounds with the help of alkali ions by placing an alkali chip such as R on a nozzle and vaporizing the alkali using the heat of the flame.

Specific examples include those that use a single crystal, those that coat a wire with water glass, those that envelop the alkali salt at the bottom of the flame, and those that use vaporized steam when the alkali salt is heated in a cylinder. etc. These publicly known examples have the advantage that their purpose can be achieved very easily, but on the other hand,
Despite consuming a large amount of alkali salt over time, there is no supply of these salts at all, so sensitivity changes moment by moment due to changes in alkali concentration or chip shape, etc., and the effective measurement time is short. have. For this reason, a calibration curve cannot be quantitatively determined unless an actual sample is prepared immediately before measurement, and it also has the disadvantage that it takes several hours to stabilize.

Despite the excellent features mentioned above, this is the reason why it is hardly used in general analysis. An object of the present invention is to provide a thermal ionization detector with stable sensitivity over a long period of time.

The present invention uses air to suck up a liquid alkali source and send it to a detector to use it as an alkali ion source.

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

The thermal ionization detector consists of a detector body 1, a nozzle 2, a hydrogen supply pipe 3, an air alkali supply pipe 4, a separation column 5, an O-ring 6, a washer 7, a cap nut 8, and an electrode plate 9.

A nozzle 2 is attached to the upper part of the detector body 1 with a screw or the like. Further, a hydrogen supply pipe 3 is attached to one side of the detector body 1, and an air and alkali supply pipe 4 are connected to the other side. Furthermore, a separation column 5 is inserted into the bottom of the detector body 1, and is fixed by an O-ring 6, a washer 7, and a cap nut 8, respectively. Each of the hydrogen supply pipe 3, the air/alkali supply pipe 4, and the separation column 5 has a structure capable of supplying gas into the nozzle. Note that electrode plates 10 are disposed on both sides facing the flame generated from the nozzle 2 at an appropriate distance. Gases in standard conditions generally have no conductivity. However, when gas molecules are given enough energy to ionize, they become charged atoms or molecules.
When free electrons are generated, the gas becomes conductive by applying an appropriate external electric field.
A flame is used as the energy source, and a battery 11 is used as the electric field. The voltage change that occurs in the resistor 12 due to this is read by the recorder 13. The air/alkali supply pipe 4 branches from the middle, and the inner diameter of this branch part is narrowed, air is supplied from one side, and the branch pipe 14 stores liquid in the alkaline source container 15. Immersed in Alkaline 16.

The operation of the embodiment with the above configuration will be described below.

A carrier gas and a sample are supplied to the detector body 1 through a separation column 5 in the direction of the arrow shown in FIG. 1, and H2 gas as fuel is supplied to the nozzle 2 from a hydrogen supply pipe 3.

When air is supplied from one side of the air/alkali supply pipe 4, the inside of the branch pipe 14 becomes depressurized due to the so-called Bernoulli's theorem, and the alkali 1 river 6 (for example, alkaline salt liquid)
is sucked up and transported to the nozzle 2 in the form of mist by the air. Then, the sample is ionized together with the heat of the flame formed at the tip of the nozzle 2, converted into an electrical signal, and recorded on the recorder 13. As an alkali source (alkali 16), alkali metals such as Rb, K, Cs, and Na, sulfates of alkaline earth metals, nitrates, halides, etc. are effective, and considering the names of these materials, an aqueous solution is the most effective. Although it is easy to handle, if a soluble organic solvent is available, it may be used as a solution of an organic solvent or in a molten state by heating. FIG. 2 is a front sectional view of the alkaline source replenishing device according to the present invention. In the embodiment shown in FIG. 1, the operation as a TID continues as long as an alkali source exists in the alkali source container 15, but there is a limit to the effective time, and for long-term continuous measurements, the alkali source is supplied after a predetermined time. There is a need.

In addition, the water level of the alkali source gradually decreases, and strictly speaking, the pressure applied to the branch pipe decreases, and the amount of alkali supplied also decreases. However, as shown in FIG. 2, when the alkaline source container 15 is at a predetermined height position of the alkaline source, the replenishing alkali source container 18,
If an alkali replenishment device consisting of the replenishment alkali supply pipe 19 is installed, the liquid level is always kept constant based on the siphon principle. Moreover, since the supplementary alkali source 17 is in a sealed state and there is no evaporation from there, the concentration in the alkali source container 15 is kept constant. Therefore, a constant amount of alkali is supplied to the detector at a constant concentration, and a TID with stable sensitivity can be obtained over a long period of time. The effects obtained by the embodiments of the present invention are listed below. (1) Sensitivity is always constant because a constant amount of alkali is always supplied at a constant concentration.

(2) Since a constant amount of alkali is always supplied at a constant concentration, the time required to reach a stable state can be significantly shortened.

(3) Supply and exchange of alkaline sources can be performed easily and easily.

Moreover, there is the advantage that there is no need to interrupt measurement for replacement operations. (4) Since continuous replenishment is possible, measurement time can be unlimited.

(5) No elaborate alkali supply pipe is required.

The flow rate of H2 and carrier gas has a great effect on sensitivity, but since there is a plateau region over a wide range of air flow rates, in order to achieve the highest sensitivity, it is sufficient to control the amount of alkali by changing the amount of air. There is no need to worry about differences in performance due to the manufacturing rod of the suction device. FIG. 3 is a side sectional view showing an application example of the present invention.

FIG. 3 shows a modification of the connection between the air/alkali supply pipe and the nozzle, so that the alkali source is supplied from outside the nozzle. In this way, the flow path systems for air, carrier gas, and H2 can be separated.
The effects obtained with this embodiment are similar to those of the embodiment of FIG. Although the embodiment of the present invention is based on the so-called Bernoulli's theorem, a configuration in which the air is blown into the air supply pipe by an ultrasonic device can also be easily realized. As is clear from the above, according to the present invention, a thermal ionization detector with stable sensitivity over a long period of time can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic view showing an embodiment of the present invention, FIG. 2 is a front sectional view of an alkali source replenishing device according to the invention, and FIG. 3 is a front sectional view showing an application example of the invention. 1...Detector body, 2...Nozzle,
3... H2 supply pipe, 4... Air/alkali supply pipe, 5... Separation column, 10 electrode plates,
14... Branch pipe, 15... Alkali source container, 16... Alkali source, 17...
Supply alkali source, 18...Supplementary alkali source container, 19...Supplementary alkali supply pipe.

Claims (1)

[Claims] 1. A thermal ionization detector comprising a nozzle to which a carrier gas and a sample are supplied, and a detection electrode provided near the nozzle, in which a metal salt for supplying ions is supplied to the nozzle. A thermal ionization detector comprising: a solution; and feeding means for atomizing or vaporizing the metal salt solution and supplying the atomized solution to the nozzle. 2. A constriction is provided in the middle of the supply pipe that supplies air to the nozzle, and a branch pipe whose end is submerged in the metal salt solution is connected from the constriction, so that the air flowing through the supply pipe is used to 2. The thermal ionization detector according to claim 1, wherein a reduced pressure is generated in the branch pipe, and the reduced pressure causes the metal salt solution to be released into the supply pipe. 3. A container having a supply pipe whose end is in contact with the liquid level of the metal salt solution connected to the bottom and containing the metal solution at a position higher than the liquid level of the metal salt solution and installed in a sealed state;
A thermal ionization detector according to claim 1 or 2, characterized in that the thermal ionization detector is equipped with a replenishing device consisting of.