Spray head assembly of hydrogen flame ionization detector

Abstract

The invention discloses a nozzle assembly of a hydrogen flame ionization detector, the nozzle assembly comprises a hollow base, an insulating tube, a frustum-shaped nozzle seat and a fine nozzle which are coaxially arranged, the base is fixedly connected with the insulating tube, the top end of the insulating tube is fixedly connected with the frustum-shaped nozzle seat, and the frustum-shaped nozzle seat is fixedly connected with the fine nozzle; a first circular through hole penetrating through the interior of the base is formed in the base, a circular groove is formed in the upper end of the base, the diameter of the circular groove is larger than the outer diameter of the insulating tube, and a second circular through hole penetrating through the interior of the insulating tube is formed in the insulating tube. According to the assembly, under the action of the applied polarization voltage, the charge density of the end of the fine nozzle is larger, compared with a common nozzle, a stronger electric field gradient is obtained near the fine nozzle under the same polarization voltage, the ionization efficiency is improved, signals are improved, and the detection limit is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen flame ionization detectors, and particularly to a nozzle assembly of a hydrogen flame ionization detector. Background Art

[0002] A hydrogen flame ionization detector (FID) is the most widely used detector on gas chromatographs and is widely used in the detection of volatile hydrocarbons and carbon-containing compounds. The FID uses a hydrogen flame as the ionization source. When the substance to be measured enters the flame, chemical ionization occurs at high temperature, and the number of ions generated after ionization is much larger than the ions generated by the combustion of hydrogen in the base current. The generated ions move directionally under the action of a high-voltage electric field to form an ion current. The ion current is amplified by a high resistance to generate an electrical signal, and the generated electrical signal is proportional to the amount of organic compounds entering the flame for combustion. Subsequently, quantitative analysis can be performed based on the electrical signal to obtain the detection result. The advantages of the FID are that it responds to almost all organic compounds, especially has high sensitivity to hydrocarbon compounds (ppb level, about 10 -13 g / s), has a wide linear range (about 6 - 7 orders of magnitude), and a fast response speed (≤1ms); changes in conditions such as gas flow rate, pressure, and temperature have little impact on its response. In the prior art, the nozzle of the hydrogen flame ionization detector has no tip enhancement design, and there is still room for improvement in aspects such as improving ion collection efficiency and ionization rate, and reducing dead volume. Summary of the Invention

[0003] In order to further improve the hydrogen flame ionization detector, the present invention proposes a nozzle assembly of a hydrogen flame ionization detector, which designs a nozzle with a tip. Compared with a nozzle without a tip, a stronger electric field can be obtained under the same polarization voltage, improving ion collection efficiency, and possibly generating secondary ionization to improve ionization efficiency, thus increasing the signal; in addition, a multi-stage stepped hole is arranged inside the nozzle to reduce dead volume and prevent peak broadening, so as to improve the performance of the detector.

[0004] The technical solution of the present invention:

[0005] A nozzle assembly of a hydrogen flame ionization detector, comprising a coaxial hollow base, an insulating tube, a frustum-shaped nozzle seat and a fine nozzle; the base is a columnar body with a through circular through-hole 1, and has a circular groove at the upper part, the diameter of which is larger than the outer diameter of the insulating tube; the insulating tube is a cylinder with a through circular through-hole 2; the frustum-shaped nozzle seat includes a lower cylinder and an upper frustum, and has a circular through-hole 3, a circular through-hole 4 and a frustum-shaped through-hole; the diameter of the circular through-hole 3 is larger than the outer diameter of the insulating tube, the diameter of the circular through-hole 4 is smaller than the diameter of the circular through-hole 3, the maximum diameter of the frustum-shaped through-hole is the same as the diameter of the circular through-hole 4, and the maximum diameter end is connected to the circular through-hole 4, the diameter of the circular through-hole 5 is the same as the minimum diameter of the frustum-shaped through-hole, and is connected to the minimum diameter end of the frustum-shaped through-hole. The diameters of the circular through-hole 1, the circular through-hole 2, the circular through-hole 3 and the circular through-hole 4 are adapted to ensure smooth gas flow. The inner diameter of the circular groove is adapted to the outer diameter of the insulating tube, and the outer diameter of the insulating tube is adapted to the diameter of the through-hole 3, and they are all sealed and connected by means of high-temperature resistant glue or the like.

[0006] The frustum-shaped nozzle seat and the fine nozzle are an integrated component or are sealed and connected by means of high-temperature resistant glue or the like. The materials of the base, the frustum-shaped nozzle seat and the fine nozzle are metals; the material of the insulating tube is a material with high temperature resistance and an insulation resistance greater than 10 10 ohms, preferably ceramics and quartz.

[0007] Under the action of the applied polarization voltage, the charge density at the end of the fine nozzle is greater. Compared with an ordinary nozzle, a stronger electric field gradient is obtained near the fine nozzle under the same polarization voltage, improving the ionization efficiency and increasing the signal; and the circular stepped through-hole provided inside the nozzle effectively reduces the internal dead volume and prevents peak broadening.

[0008] For a nozzle assembly of a hydrogen flame ionization detector disclosed in the present invention, under the action of the applied polarization voltage, the charge density at the end of the fine nozzle is greater. Compared with an ordinary nozzle, a stronger electric field gradient is obtained near the fine nozzle under the same polarization voltage, improving the ionization efficiency, increasing the signal and reducing the detection limit. The circular stepped through-hole provided inside the nozzle assembly effectively reduces the internal dead volume and prevents peak broadening. Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0010] Figure 1 It is a schematic cross-sectional view of the nozzle assembly of the present invention

[0011] Figure 2 This is a disassembled schematic diagram of the spray head assembly of the present invention.

[0012] Figure 3 This is a comparison chart of the FID chromatograms of the spray head assembly using this technical solution and that of a common nozzle.

[0013] In the figure: 1. Base, 2. Insulating tube, 3. Table conical nozzle seat, 4. Fine nozzle, 11. Circular through hole one, 12. Circular groove, 21. Circular through hole two, 31. Circular through hole three, 32. Circular through hole four, 33. Frustum-shaped through hole, 41. Circular through hole five. Detailed implementation manners

[0014] To make the technical solution and advantages of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention:

[0015] As Figure 1 shown, a spray head assembly of a hydrogen flame ionization detector includes a base 1, an insulating tube 2, a table conical nozzle seat 3, and a fine nozzle 4 with a hollow structure coaxially arranged; the base 1 is a columnar body with a circular through hole one 11 penetrating through it, and there is a circular groove 12 on the upper part, and the diameter of the circular groove 12 is larger than the outer diameter of the insulating tube 2; the insulating tube 2 is a cylinder with a circular through hole two 21 penetrating through it; the table conical nozzle seat 3 includes a cylinder at the lower part and a frustum at the upper part, and there are a circular through hole three 31, a circular through hole four 32, and a frustum-shaped through hole 33 inside; the diameter of the circular through hole three 31 is larger than the outer diameter of the insulating tube 2, the diameter of the circular through hole four 32 is smaller than the diameter of the circular through hole three 31, the maximum diameter of the frustum-shaped through hole 33 is the same as the diameter of the circular through hole four 32, and the maximum diameter end is connected to the circular through hole four 32; there is a circular through hole five 41 inside the fine nozzle 4, and the diameter of the circular through hole five 41 is the same as the minimum diameter of the frustum-shaped through hole 33.

[0016] Embodiment:

[0017] The diameter of the circular through hole one 11 is 1 mm, and the inner diameter of the groove 12 is 2.8 mm; the outer diameter of the insulating tube 2 is 2.5 mm, which is adapted to the inner diameter of the groove 12, and the length is 13 mm, and the diameter of the circular through hole two 21 is 1 mm; the outer diameter of the cylinder at the lower part of the table conical nozzle seat 3 is 4.6 mm, the frustum cone angle of the upper part is 40°, the diameter of the circular through hole three 31 is 2.8 mm, which is adapted to the outer diameter of the insulating tube 2; the diameter of the circular through hole four 32 is 1 mm, the diameter of the maximum diameter end of the frustum-shaped through hole 33 is 1 mm, which is the same as the diameter of the circular through hole four 32, and the diameter of the minimum diameter end of the frustum-shaped through hole 33 is 0.2 mm; the outer diameter of the fine nozzle 4 is 0.5 mm, the length is 0.5 mm, the diameter of the circular through hole five 41 is 0.2 mm, which is the same as the diameter of the minimum diameter end of the frustum-shaped through hole 33.

[0018] Apply the hydrogen flame ionization detector nozzle assembly proposed in this embodiment to the detection of n-hexadecane / isooctane. The chromatographic conditions are as follows: injection port temperature 300 °C, carrier gas: nitrogen (purity 99.999%), OV-1 chromatographic column, inner diameter 0.32 mm, length 30 m, film thickness 0.4 μm; carrier gas flow rate of the chromatographic column 1 mL / min. Injection port 220 °C, column oven 150 °C, detector 315 °C, inject 100 ppm n-hexadecane / isooctane, injection volume 0.2 μL, split ratio 1:10.

[0019] Figure 3 Figure 4 is a comparison chart of the FID chromatograms of the FID using the nozzle assembly of this technical solution and the FID of a common nozzle. As can be seen from the figure, the FID signal of the FID using the nozzle assembly of this technical solution is 4.1 times that of the FID signal of the nozzle without a tip, indicating that the technology of using the nozzle assembly of this technical solution has achieved the technical effects of improving the FID signal and reducing the signal ratio.

[0020] Further, the outer diameter of the fine nozzle 4 of the nozzle is 0.8 mm and the length is 5 mm.

[0021] Further, the outer diameter of the fine nozzle 4 is 0.4 mm and the length is 0.5 mm.

[0022] Further, the diameter of the smallest diameter end of the frustum-shaped through hole 33 and the diameter of the circular through hole five 41 are both 0.05 mm.

[0023] Further, the diameter of the smallest diameter end of the frustum-shaped through hole 33 and the diameter of the circular through hole five 41 are both 0.4 mm.

[0024] Further, the apex angle of the frustum at the upper part of the nozzle cone-shaped nozzle seat 3 is 60°.

[0025] Further, the apex angle of the frustum at the upper part of the nozzle cone-shaped nozzle seat 3 is 20°.

[0026] Further, the diameters of the circular through hole one 11, the circular through hole two 21, the circular through hole three 31 and the circular through hole four 32 are all 0.3 mm.

[0027] Further, the diameters of the circular through hole one 11, the circular through hole two 21, the circular through hole three 31 and the circular through hole four 32 are all 3 mm.

[0028] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A nozzle assembly for a hydrogen flame ionization detector, characterized in that: it includes a base (1) with a hollow structure, an insulating tube (2), a frustum-shaped nozzle seat (3) and a fine nozzle (4) which are coaxially arranged. The base (1) is fixedly connected to the insulating tube (2), the top end of the insulating tube (2) is fixedly connected to the frustum-shaped nozzle seat (3), and the frustum-shaped nozzle seat (3) is fixedly connected to the fine nozzle (4); a circular through-hole one (11) penetrating through its interior is provided on the base (1), a circular groove (12) is provided at the upper end of the base (1), the diameter of the circular groove (12) is larger than the outer diameter of the insulating tube (2), and a circular through-hole two (21) penetrating through its interior is provided on the insulating tube (2); The frustum-shaped nozzle seat (3) includes a cylinder at the lower part and a frustum at the upper part. A circular through-hole three (31), a circular through-hole four (32) and a frustum-shaped through-hole (33) are provided inside the frustum-shaped nozzle seat (3). The diameter of the circular through-hole three (31) is larger than the outer diameter of the insulating tube (2), the diameter of the circular through-hole four (32) is smaller than the diameter of the circular through-hole three (31), the maximum diameter of the frustum-shaped through-hole (33) is the same as the diameter of the circular through-hole four (32), and the maximum diameter end is connected to the circular through-hole four (32); There is a circular through-hole five (41) inside the fine nozzle (4), and the diameter of the circular through-hole five (41) is the same as the minimum diameter of the frustum-shaped through-hole (33).

2. The nozzle assembly for a hydrogen flame ionization detector according to claim 1, characterized in that: The base (1) is a columnar body, and the insulating tube (2) is a cylindrical body; the base (1), the table-cone-shaped nozzle base (3), and the fine nozzle (4) are made of metal, and the insulating tube (2) is made of a material that is heat-resistant and has an insulation resistance greater than 10 10 ohms.

3. The nozzle assembly for a hydrogen flame ionization detector according to claim 1, characterized in that: the outer diameter of the insulating tube (2) is 1 - 5 mm, the length is 1 - 20 mm, and the diameter of the circular through-hole two (21) is 0.3 - 3 mm; The diameter of the circular through-hole one (11) is 0.3 - 3 mm, and the inner diameter of the circular groove (12) is 0.1 - 1 mm larger than the outer diameter of the insulating tube (2); The outer diameter of the cylinder at the lower part of the frustum-shaped nozzle seat (3) is 4 - 20 mm, the frustum angle of the frustum at the upper part is 20° - 60°, the diameter of the circular through-hole three (31) is 0.1 - 1 mm larger than the outer diameter of the insulating tube (2), the diameter of the circular through-hole four (32) is 0.3 - 1 mm, the maximum diameter of the frustum-shaped through-hole (33) is 0.3 - 1 mm and is the same as the diameter of the circular through-hole four (32), and the minimum diameter of the frustum-shaped through-hole (33) is 0.05 - 0.4 mm; The outer diameter of the fine nozzle (4) is 0.4 - 0.8 mm, the length is 0.5 - 5 mm, and the diameter of the circular through-hole five (41) is 0.05 - 0.4 mm and is the same as the minimum diameter of the frustum-shaped through-hole (33).

4. The nozzle assembly for a hydrogen flame ionization detector according to claim 1, characterized in that: the base (1) is hermetically connected to the insulating tube (2), and the insulating tube (2) is hermetically connected to the frustum-shaped nozzle seat (3).

5. The nozzle assembly for a hydrogen flame ionization detector according to claim 1, characterized in that: The conical nozzle seat (3) and the fine nozzle (4) are an integrated component or are hermetically connected.

6. The nozzle assembly of a hydrogen flame ionization detector according to claim 1, characterized in that: The material of the insulating tube (2) is ceramic or quartz.

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