WO2009118825A1

WO2009118825A1 - Gas chromatograph

Info

Publication number: WO2009118825A1
Application number: PCT/JP2008/055542
Authority: WO
Inventors: 尚弘西本; 正樹叶井; 正憲西野
Original assignee: 株式会社島津製作所
Priority date: 2008-03-25
Filing date: 2008-03-25
Publication date: 2009-10-01
Also published as: JPWO2009118825A1; JP4840532B2

Abstract

[PROBLEMS] To realize the positioning accuracy at injector replacement by simple arrangement and thermally separate the injector from an insert. [MEANS FOR SOLVING PROBLEMS] A base board (2) comprises an injector area (13) having a first positioning part (14) for positioning of an injector (4) in order to attain mutually positioning of the injector (4) and an insert (6), and an insert area (28) having a second positioning part (30) for positioning of the insert (6) so that the center of a discharge port (8) of the injector (4) and the center of a sample inlet (20) of the insert (6) lie on the same straight line. Further, the base board (2) comprises a thermal insulation area (38) disposed between the injector area (13) and the insert area (28) in order to thermally separate them.

Description

Gas chromatograph

The present invention relates to a gas chromatograph, and more particularly to a gas chromatograph provided with an injector for discharging a sample by a piezoelectric element.

In general, a gas chromatograph has a configuration in which an inlet of a separation column is connected to an insert, a liquid sample is injected into the insert using a microsyringe, vaporized, and the vaporized sample is placed on a carrier gas and sent into the separation column. .

Sample injection with a microsyringe is difficult to inject a very small amount of sample. Therefore, recently, an ultra-small amount of injector using an ink jet technology capable of discharging a liquid by a piezoelectric element has been developed, and it is possible to inject a sample on the order of pL to nL, which is impossible with a microsyringe (non-patent document). 1).
Analytical Chemistry Vol.54, No.6, pp.533-539 (2005) P. Steiner et al., Micromachining applications of porous silicon, Thin Solid Films 255 (1995) 52-58

When using an injector with a piezoelectric element, unlike a conventional syringe, there is no needle, so high-precision alignment is required between the injector outlet and the inlet of the insert. For example, using a capillary column as a separation column, in the case where one end connected to insert the capillary column has an inner diameter of about capillary has an inner diameter center and the injector discharge port of the insert about 320 .mu.m (e.g. 78 .mu.m × 38 [mu] m) Must be accurately aligned with the center of the.

Injectors and inserts need to be replaced due to dirt, etc., and precise alignment between the injector and the insert is required every time it is replaced, so there are problems such as complicated and time-consuming operations for injector replacement and insert replacement. there were. Therefore, there is a demand for easy replacement of injectors and inserts while ensuring positioning accuracy.

Also, in order to ensure positioning accuracy, it is necessary to fix the injector and insert to the integrated positioning mechanism. Since the insert must be heated for vaporizing the sample, the heat is heated up to the injector through the alignment mechanism, and there is a problem that the discharge mechanism of the injector is damaged.

An object of the present invention is to provide a gas chromatograph provided with a mechanism that can realize the alignment accuracy at the time of injector replacement with a simple structure and can thermally separate the injector from the insert.

In order to solve the above-mentioned problems, the gas chromatograph apparatus according to the present invention is configured such that the injector and the insert are connected by a member having a positioning function to perform alignment. In addition, the member having the positioning mechanism includes a heating mechanism for heating the insert and a heat insulating portion between the injector and the insert, so that the insert is heated in a state in which heat is not easily transmitted to the injector portion, and the sample is It has a structure that can be vaporized.

That is, the gas chromatograph according to the present invention includes an injector that discharges a sample by a piezoelectric element, a sample inlet that receives a sample discharged from the injector, a heating unit that heats and vaporizes the received sample, and an exhaust that discharges the vaporized sample. An insert having an outlet, a base for positioning the injector and the insert, a heater arranged to heat the insert in the insert heating region of the base, a sample outlet of the injector, and a sample inlet of the insert are shared. A sealed container having a carrier gas supply port to which carrier gas is supplied so as to be included in the internal space, a separation column connected to the discharge port of the insert, and a detector connected downstream of the separation column ing.

In order to position the injector and the insert relative to each other, the base is inserted so that the injector area having the first positioning portion for positioning the injector, the center of the discharge port of the injector and the center of the sample inlet of the insert are on the same straight line And an insert region having a second positioning portion for positioning.

Furthermore, the base is provided with a heat insulating region arranged between the injector region and the insert region in order to thermally separate the injector region and the insert region.

It is preferable that the insert has a cylindrical outer shape. In that case, it is preferable that the base is made of a silicon substrate, and the second positioning portion is a groove having a V-shaped cross section formed by anisotropic wet etching of the silicon substrate. The insert is positioned by being fitted into the groove of the second positioning portion.

An example of a separation column is a capillary column. In that case, the insert is connected to the capillary column so that its internal space communicates with the capillary column, and the sample inlet of the insert has a diameter of 1 mm or less. Thus, if the sample inlet of the insert is made small, the insert itself can be made small and the heat capacity of the insert can be made small, so that the temperature can be rapidly raised and high-speed analysis becomes possible. In addition, the insert volume needs to correspond to the volume increase at the time of sample vaporization, but since it is for a small amount sample of about nL as a liquid, it is about μL in a gas state, has a diameter of 1 mm or less, and several mm There is no problem with the length of insert.

As the injector, one having a rectangular flat bottom surface can be used. In that case, if the first positioning portion is a recess having a flat surface formed on the base, and the bottom surface of the recess is formed in a shape that matches the shape of the bottom surface of the injector, the injector is in the recess. Positioning is performed by fitting.

When the base is made of a silicon substrate, the heat insulating region can be a region made of porous silicon dioxide formed on the base. The heat insulating region made of porous silicon dioxide is specifically described later, but by selectively treating the silicon substrate between the injector region and the insert region, the silicon substrate is integrated with the injector region and the insert region. Can be formed.

A preferable example of the heater is a metal thin film resistor formed on a base.

By attaching the injector and the insert to the base having the alignment function, the distance between the injector and the insert can be made constant, and the center of the injector outlet and the center of the sample inlet of the insert can be aligned. In the gas chromatograph of the present invention, it is possible to easily perform positioning at the time of injector replacement while corresponding to the introduction of a small amount of sample using an ink jet type injector, so that the replacement time of the injector can be greatly shortened, Performance degradation due to poor alignment is prevented and stable measurement is possible.

FIG. 1A is for showing the outline of the sample injection part of the gas chromatograph of one Example.

FIG. 1B is a front view of the same embodiment.

1C is a cross-sectional view taken along the line CC of FIG. 1A.

FIG. 1D is a cross-sectional view showing a connection state between the insert and the capillary column.

FIG. 2 is a perspective view showing the base and the injector and the insert positioned and fixed to the base.

FIG. 3 is a process diagram illustrating a method of manufacturing a base in the order of processes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Base 4 Injector 6 Insert 8 Discharge port 13 Injector area | region 14 Recessed part as 1st positioning part 18 Airtight container 20 Sample inlet 22 Heating part 24 Outlet 26 Capillary column as a separation column 28 Insert area | region 32 Heater 38 Thermal insulation area | region 40 Caer gas Supply port 42 Detector

Hereinafter, an embodiment of the present invention will be described in detail.
1A to 1D are schematic configuration diagrams of a gas chromatograph of one embodiment. FIG. 1A is a plan view of a sample injection portion, and shows a part in a sectional view through a sealed container. FIG. 1B is a front view of the same embodiment, showing the sealed container and the insert through. 1C is a cross-sectional view taken along the line CC in FIG. 1A, and FIG. 1D is a cross-sectional view showing a connection state between the insert and the capillary column. FIG. 2 is a perspective view showing the base and the injector and the insert positioned and fixed to the base.

The base 2 is made of a silicon substrate, and the injector 4 and the insert 6 are positioned and fixed.

The injector 4 is of an ink jet type in which a sample is ejected by a piezoelectric element, and has an outer shape of a rectangular parallelepiped and a rectangular flat bottom surface. A sample supply pipe that has a discharge port 8 for discharging a sample at the tip surface of the injector 4, that is, the end surface facing the insert 6 when positioned on the base 2, and a sample is supplied from the outside to the opposite end surface 10 is connected. An actuator 12 made of a piezoelectric element is provided on the upper surface of the injector 4 in order to discharge the sample supplied from the sample supply pipe 10 as a droplet from the discharge port 8.

The base 2 has an injector region 13 for positioning the injector 4 on the base 2, and a concave portion 14 having a flat bottom surface is formed in the injector region 13 as a first positioning portion for positioning the injector 4. . The bottom surface of the concave portion 14 is formed in a shape that matches the bottom surface shape of the injector 2, and the injector 2 is positioned by being fitted into the concave portion 14.

In order to fix the injector 4 in the recess 14 of the base 2, a pressing spring 16 is provided. The holding spring 16 has a base end fixed to the hermetic container 18, and the injector 4 is fixed in a state of being positioned with respect to the base 2 by pressing the injector 4 toward the base 2 at the tip end.

The insert 6 has a cylindrical outer shape, and has a sample inlet 20 that receives a sample discharged from the injector 4, a heating unit 22 that heats and vaporizes the received sample, and an outlet 24 that discharges the vaporized sample. An end of the capillary column 26 is inserted into the discharge port 24 as a separation column. The inner space of the insert 6 communicates with the capillary column 26, and the central axis of the insert 6 and the central axis of the capillary column 26 are the same. The insert 6 and the capillary column 26 are connected so as to be in a straight line. The insert 6 has an outer diameter of 500 μm, and the sample inlet 20 has a diameter of, for example, 300 μm.

In order to position the insert 6 on the base 2, an insert region 28 is provided in the base 2. In the insert region 28, a groove 28 having a V-shaped cross section is formed as a second positioning portion so that the center of the discharge port 8 of the injector 4 and the center of the sample inlet 20 of the insert are on the same straight line. . The groove 28 is formed by anisotropic wet etching of the silicon substrate of the base 2 with an alkaline solution. The insert 6 is positioned by being fitted into the groove 28. Similarly to the injector 4, the insert 6 is also fixed by being pressed by an appropriate member (not shown) such as a holding spring.

A heater 32 is provided in the insert region 28 of the base 2 so as to heat the heating part 22 of the insert 6. The heater 32 is made of a Ni—Cr alloy or the like, and is a metal thin film resistor having a thickness of 1 to 10 μm formed by vapor deposition or sputtering through a mask having an opening in a predetermined region of the insert region 28. Lead

wires

34 and 36 for energization are connected to the heater 32.

In the base 2, a heat insulating region 38 made of porous silicon dioxide is formed between the injector region 13 and the insert region 28. The heat insulating region 38 is for preventing the heat of the heater 32 from being transmitted to the injector region 13. The heat insulating region 38 is formed so as to reach from the surface to the bottom surface in the thickness direction of the base 2 over the entire width of the base 2 in order to thermally shield between the injector region 13 and the insert region 28.

In order to vaporize the sample injected into the insert 6 from the injector 4 and send it to the capillary column 26 together with the flow of the carrier gas, a sealed container 18 covering the injector 4 and the insert 6 is provided. A carrier gas supply port 40 through which gas is supplied is provided. The sample supply pipe 10 penetrates the sealed container 18 and is connected to the injector 4 from the outside, the capillary column 26 penetrates the sealed container 18 and is guided to the outside, and the

lead wires

34 and 36 also penetrate the sealed container 18 to the outside. Has been led to.

The sealed container 18 covers the sample discharge port 8 of the injector 4 and the sample inlet 20 of the insert 6 in a common internal space, and the carrier gas is supplied from the carrier gas supply port 40 to the internal space, whereby the insert 6 The sample that has been injected into and vaporized is fed into the capillary column 26 by the carrier gas and separated.

In order to detect the sample component separated by the capillary column 26, a detector 42 is connected downstream of the capillary column 26. As the detector 42, an FID (hydrogen flame ionization detector) or the like can be used.

The discharge amount of the ink jet injector 4 of this embodiment is smaller than that of a conventional microsyringe, and is usually about several pL to several tens of nL / 1 drop. In this embodiment, the injector 4 is manufactured in a chip shape using MEMS (micro electro mechanical system) technology, and its outer shape is usually determined by cutting using a precision processing machine such as a dicing saw. Therefore, it is produced with an accuracy of the order of μm.

For the insert, for example, when the outer shape is 500 μm, the tolerance is about ± 20 μm. By using the V-shaped groove 30 formed on the base 2 of the silicon substrate, positioning can be performed with an accuracy of the order of 10 μm.

Next, a method for producing the base 2 as the positioning member will be described with reference to FIG.

(1) The silicon substrate 50 to be the base 2 has a surface crystal plane of (100) and has a low resistivity. First, the silicon substrate 50 is thermally oxidized to form an oxide film 52 on the surface. This oxide film 52 becomes a protective film for later etching. Instead of the oxide film 52, a silicon nitride film may be formed by a technique such as CVD (chemical vapor deposition).

(2) A photomask pattern is transferred to the photoresist layer 54 on the oxide film 52 by photolithography, and an opening 56 for forming a recess for positioning the injector and a V-groove for positioning the insert are formed. For this purpose, an opening 58 is formed. The opening 58 for forming the V-groove is rectangular, and its longitudinal direction is aligned with the <110> axial direction of the silicon substrate 50.

(3) The oxide film 52 in the

openings

56 and 58 is removed by wet etching using a chemical solution such as buffered hydrofluoric acid or by dry etching using a gas such as CF ₄ .

(4) The photoresist layer 54 is removed, and etching is performed using a chemical solution capable of anisotropic etching with different etching rates depending on the silicon crystal orientation, such as KOH (potassium hydroxide) and TMAH (tetramethylammonium hydroxide). . At this time, in the V groove forming opening 58, the surface orientation of the surface of the silicon substrate 50 is (100), and the opening 58 is aligned with the <110> direction. Low (111) plane appears, and a groove 30 having a V-shaped cross section is formed.

On the other hand, since the recess opening 56 for positioning the injector has a large etching area, the etching of the (100) plane is finished before the line intersecting the (111) plane appears, and the recess 14 having a flat bottom surface is formed. It is formed.

The following process is a process for forming a thermal insulating layer made of porous silicon oxide (see Non-Patent Document 2).

(5) First, an Au thin film 60 is formed by vapor deposition on the surface of the silicon substrate 50 where the recesses 14 and the grooves 30 are formed.

(6) A resist pattern is formed on the surface of the Au thin film 60 by photolithography, and etching is performed with an Au etchant to selectively remove the Au thin film in the region where the thermal insulating layer is to be formed or to form the opening 62. The opening 62 is formed so as to cross the surface of the silicon substrate 50 in the width direction.

(7) After removing the resist, the opening 62 of the Au thin film 60 is anodized in a mixed solution of HF: water: ethanol = 2: 2: 2 at a current density of 240 mA / cm ² for 60 minutes to form a silicon substrate. The portion is converted into a porous silicon layer 64. At this time, the porous silicon layer 64 formed by anodization is formed isotropically and has a depth of about 300 μm.

(8) The Au thin film 60 on the silicon substrate surface is removed and thermal oxidation is performed. At this time, an oxide film layer 66 of about 0.3 μm is formed on the surface of the silicon substrate under conditions of wet oxidation at 1000 ° C. for 30 minutes. On the other hand, since the porous silicon layer 64 has a high oxidation rate, the entire layer becomes the porous silicon oxide 38.

(9) A heater 22 is formed by forming a metal film serving as a resistor by a mask vapor deposition method or a mask sputtering method.

(10) The end face on the capillary connection side of the silicon substrate 50 is cut at a position on the groove 30 with a dicing saw, and the V-shaped end face of the groove 30 is exposed to the end face of the silicon substrate 50.

If the silicon substrate 50 having a thickness of about 300 μm is used, it can be made porous in the entire thickness direction in the step (7). The recess 14 at the fixed position of the injector chip is formed with a depth of about 200 μm. If an injector chip having a discharge port height of about 500 μm from the bottom surface of the chip is used, the straight line connecting the injector discharge port and the sample inlet of the insert is 200 μm above the silicon substrate surface. On the other hand, if the depth of the V-groove 30 is 205 μm from the surface of the silicon substrate, when an insert having an outer diameter of 500 μm is used, it is in line with the discharge port of the injector.

The injector chip 4 and the insert 6 are arranged on the base 2 of the alignment member manufactured as described above. Since the bottom surface of the recess 14 for arranging the injector chip 4 is formed according to the shape of the bottom surface of the injector chip, it can be fixed at a position aligned with the center of the insert 6. The fixing is exemplified by fixing with the presser spring 16 in consideration of chip replacement, but is not limited to this as long as the chip can be easily replaced.

Claims

An injector for discharging a sample by a piezoelectric element;
A sample inlet for receiving the sample discharged from the injector, a heating section for heating and vaporizing the received sample, and an insert having a discharge port for discharging the vaporized sample;
An injector region having a first positioning part for positioning the injector; an insert having a second positioning part for positioning the insert so that a center of a discharge port of the injector and a center of a sample inlet of the insert are on the same straight line A base comprising a region and a heat insulating region disposed between the injector region and the insert region;
A heater arranged to heat the heating part of the insert in the insert region of the base;
Covering the sample outlet of the injector and the sample inlet of the insert in a common internal space, and a sealed container having a carrier gas supply port to which a carrier gas is supplied;
A separation column connected to the outlet of the insert;
A detector connected downstream of the separation column;
Gas chromatograph equipped with.
The insert has a cylindrical outer shape, the base is made of a silicon substrate, and the second positioning portion is a groove having a V-shaped cross section formed by anisotropic wet etching of the silicon substrate. The gas chromatograph according to claim 1, wherein the gas chromatograph is positioned by being fitted into a groove of the second positioning portion.
The separation column is a capillary column, and the insert is connected to the capillary column such that the internal space communicates with the capillary column,
The gas chromatograph according to claim 2, wherein the sample inlet of the insert has a diameter of 1 mm or less.
The bottom surface of the injector is a rectangular flat surface, the first positioning portion is a recess having a flat surface formed on the base, and the bottom surface of the recess is formed in a shape that matches the bottom surface shape of the injector. The gas chromatograph according to claim 2 or 3, wherein the injector is positioned by being fitted into the recess.
The gas chromatograph according to any one of claims 2 to 4, wherein the heat insulating region is a region made of porous silicon dioxide formed on the base.
The gas chromatograph according to any one of claims 1 to 5, wherein the heater is a metal thin film resistor formed on a base.