Comprehensive Two-Dimensional Gas Chromatograph And Modulation Method

Abstract

A comprehensive two-dimensional gas chromatograph, comprising a sample injector, a primary dimension column, a two-position three-way valve, a secondary dimension column, a three-way tube, a heating oven and a detector, wherein an inlet end(s) of the sample injector is connected to a carrier gas line and as well to a sample line, and an outlet end thereof is connected to a first end of the primary dimension column, a second end of the primary dimension column is connected to a first branch of the three-way tube, a second branch of the T-union is connected to a first end of the secondary dimension column, a second end of the secondary dimension column is connected to an inlet of the detector, a third branch of the three-way tube is connected to a gas inlet of the two-position three-way valve, and a first gas outlet of the two-position three-way valve is connected to the carrier gas line.

Claims

1. A comprehensive two-dimensional gas chromatograph, comprising a sample injector, a primary dimension column, a two-position three-way valve, a secondary dimension column, a three-way tube, a heating oven and a detector, wherein an inlet end(s) of the sample injector is connected to a carrier gas line and as well to a sample introduction means, and an outlet end thereof is connected to a first end of the primary dimension column, a second end of the primary dimension column is connected to a first branch of the three-way tube, a second branch of the three way tube is connected to a first end of the secondary dimension column, a second end of the secondary dimension column is connected to the detector, a third branch of the three-way tube is connected to a gas inlet of the two-position three-way valve, and a first gas outlet of the two-position three-way valve is connected to the carrier gas line.

2. The comprehensive two-dimensional gas chromatograph according to claim 1, wherein a second gas outlet of the two-position three-way valve is connected to a gas-venting capillary.

3. The comprehensive two-dimensional gas chromatograph according to claim 1, wherein the entireties of the primary dimension column and the secondary dimension column as well as part of the three-way tube are arranged inside the heating oven, and the two-position three-way valve is arranged outside the heating oven.

4. The comprehensive two-dimensional gas chromatograph according to claim 3, wherein in a first operational phase, the gas inlet of the two-position three-way valve is in communication for a first predetermined time t.sub.fill with the second gas outlet other than the first gas outlet; and in a second operational phase following termination of the first operational phase, the gas inlet of the two-position three-way valve is in communication for a second predetermined time t.sub.flush with the first gas outlet other than the second gas outlet.

5. The comprehensive two-dimensional gas chromatograph according to claim 4, wherein in the first predetermined time Um, the sample after primary dimension separation flows with the carrier gas into a portion of the third branch of the three-way tube that is located inside the heating oven without flowing into any portion that is located outside the heating oven.

6. The comprehensive two-dimensional gas chromatograph according to claim 4, wherein in the second predetermined time t.sub.flush, the carrier gas comes in from the first gas outlet and carries the sample present in the third branch of the three-way tube into the secondary dimension column for orthogonal separation and then into the detector for detection.

7. The comprehensive two-dimensional gas chromatograph according to claim 6, wherein the first operational phase is restarted when the second predetermined time is over.

8. A modulation method using a comprehensive two-dimensional gas chromatograph, comprising the following steps: Step 1. Flow path connections: connecting an inlet end of a sample injector to a carrier gas line and an outlet end thereof to a first end of a primary dimension column; connecting a second end of the primary dimension column to a first branch of a three-way tube; connecting a second branch of the three way tube to a first end of a secondary dimension column; connecting a second end of the secondary dimension column to a detector; connecting a third branch of the three-way tube to a gas inlet of a two-position three-way valve; and connecting a first gas outlet of the two-position three-way valve to the carrier gas line, wherein the entireties of the primary dimension column and the secondary dimension column as well as part of the three-way tube are arranged inside a heating oven, and the two-position three-way valve is arranged outside the heating oven; Step 2. Controlling the two-position three-way valve such that the gas inlet of the two-position three-way valve is in communication with a second gas outlet other than the first gas outlet for a first predetermined time t.sub.fill during which the sample after primary dimension separation flows into the third branch of the three-way tube with the carrier gas; Step 3. After the end of Step 2, controlling the two-position three-way valve such that the gas inlet of the two-position three-way valve is in communication with the first gas outlet other than the second gas outlet for a second predetermined time t.sub.flush during which the carrier gas comes in from the first gas outlet and carries the sample present in the third branch of the three-way tube into the secondary dimension column for orthogonal separation.

9. The modulation method according to claim 8, wherein the first predetermined time t.sub.fill is set such that the sample after primary dimension separation flows with the carrier gas only into a portion of the third branch of the three-way tube that is located inside the heating oven without flowing into any portion of the third branch of the three-way tube that is located outside the heating oven.

10. The modulation method according to claim 8, wherein during the t.sub.flush, only the sample present in the third branch of the three-way tube flows into the secondary dimension column for orthogonal separation and then into the detector for detection.

11. The modulation method according to claim 8, wherein Step 2 is restarted after the end of Step 3.

12. The modulation method according to claim 8, wherein Step 1 further comprises connecting the second gas outlet of the two-position three-way valve to a gas-venting capillary.

13. The modulation method according to claim 8, wherein during the t.sub.flush: (1) the pressure established between the first end and the second end of the primary dimension column is temporarily balanced and thus the gas flow in the primary dimension column is stopped without further sample separation; or (2) the pressure at the first end of the primary dimension column is slightly higher than that at the second end and thus results in a slow sample separation in the primary dimension column.

14. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is a schematic view showing the structure of the comprehensive two-dimensional gas chromatograph according to the present invention;

[0021] FIG. 2 is a schematic view illustrating a first operational phase of the comprehensive two-dimensional gas chromatograph according to the present invention;

[0022] FIG. 3 is a schematic view illustrating a second operational phase of the comprehensive two-dimensional gas chromatograph according to the present invention;

[0023] FIG. 4 is a diagram showing the result of a comprehensive two-dimensional gas chromatographic separation of a gasoline sample using the comprehensive two-dimensional gas chromatograph according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The comprehensive two-dimensional gas chromatograph according to the present invention will be described in detail below with reference to the accompanying drawings.

[0025] As shown in FIG. 1, a comprehensive two-dimensional gas chromatograph comprises a sample injector, a primary dimension column, a two-position three-way valve, a secondary dimension column, a three-way tube, a heating oven and a detector, wherein an inlet end(s) of the sample injector is connected to a carrier gas line and as well to a sample line (not shown), an outlet end thereof is connected to a first end of the primary dimension column, a second end of the primary dimension column is connected to a first branch of the three-way tube, a second branch of the T-union is connected to a first end of the secondary dimension column, and a second end of the secondary dimension column is connected to an inlet of the detector; a third branch of the three-way tube is connected to a gas inlet of the two-position three-way valve, a first gas outlet of the two-position three-way valve is connected to the carrier gas line, and a second gas outlet of the two-position three-way valve is connected to a gas-venting capillary.

[0026] The bodies of the primary dimension column and the secondary dimension column as well as part of the three-way tube are arranged inside the heating oven, and the two-position three-way valve is arranged outside the heating oven.

[0027] The operating principle of the comprehensive two-dimensional gas chromatograph of the present invention will be described below with reference to FIGS. 2 and 3. As shown in FIG. 2, in the first operational phase, the gas inlet of the two-position three-way valve is in communication with the second gas outlet other than the first gas outlet for a first predetermined time t.sub.fill during which the sample after primary dimension separation flows with the carrier gas into the third branch of the three-way tube; the first predetermined time t.sub.fill is set such that the sample after primary dimension separation flows with the carrier gas only into a portion of the third branch of the three-way tube that is located in the heating oven without flowing into any portion that is located outside the heating oven, and the inner diameter and length of the portion of the third branch of the three-way tube located inside the heating oven are set such that the inner volume is sufficient to contain the sample after primary dimension separation without allowing it to flow into the portion located outside the heating oven. After the end of the first operational phase, the second operational phase follows, and as shown in FIG. 3, the gas inlet of the two-position three-way valve is in communication with the first gas outlet other than the second gas outlet, and the carrier gas comes in from the first gas outlet and carries the sample present in the third branch of the three-way tube into the secondary dimension column for orthogonal separation for a second predetermined time t.sub.flush. During the above-mentioned second operational phase (t.sub.flush period): (1) the end-to-end pressure between the first end and the second end of the primary dimension column is temporarily balanced such that the flow of sample in the primary dimension column is stopped without further sample separation; (2) or the pressure at the first end of the primary dimension column is slightly higher than that at the second end and thus results in a slow sample separation in the primary dimension column, during which only the sample present in the third branch of the three-way tube flows into the secondary dimension column for orthogonal separation and then into the detector for detection. The first operational phase can be restarted when the second predetermined time is over. During the first operational phase, a high-pressure carrier gas equal to that in the primary dimension column still remains momentarily in the secondary dimension column and will thus prevent the carrier gas of the primary dimension column from carrying the sample into the secondary dimension column while making its way to the three-way tube.

[0028] In the present invention, the two-position three-way valve is repeatedly switched in accordance with a modulation cycle: t=t.sub.fill+t.sub.flush, thus providing continuous modulation and comprehensive two-dimensional gas chromatographic separation on the primary dimension flow.

[0029] FIG. 4 is a diagram showing a result of a comprehensive two-dimensional gas chromatographic separation on a gasoline sample using the comprehensive two-dimensional gas chromatograph of the present invention, which demonstrates the effect of the optimized device of the present invention. It can be seen from FIG. 4 that under the modulation with the comprehensive two-dimensional gas chromatograph of the present invention, the gasoline is separated in primary dimension under boiling points and separated in second dimension under polarities at one go, which results in an effective comprehensive secondary dimension separation.

[0030] In the above-mentioned embodiment, the second gas outlet of the two-position three-way valve is connected to a gas-venting capillary, which functions to increase the resistance, reduce the venting flow rate, and prevent sample loss from flowing out of the valve more effectively in time t.sub.fill. The gas-venting capillary may also be in other forms of damping elements, such as a porous gas blocker, a needle valve, and the like, all of which are however optional, i.e., the object of the present invention may also be achieved by leaving the second gas outlet of the two-position three-way valve open-ended without a gas-venting capillary being connected thereto.

[0031] Base on the comprehensive two-dimensional gas chromatograph as described above, the present invention also provides a modulation method using the same:

[0032] Step 1. Flow path connections: connecting an inlet end of a sample injector to a carrier gas line and an outlet end thereof to a first end of a primary dimension column; connecting a second end of the primary dimension column to a first branch of a three-way tube; connecting a second branch of the T-union to a first end of a secondary dimension column; connecting a second end of the secondary dimension column to an inlet of a detector; connecting a third branch of the three-way tube to a gas inlet of a two-position three-way valve; connecting a first gas outlet of the two-position three-way valve to the carrier gas line; and connecting the second gas outlet of the two-position three-way valve to a gas-venting capillary, wherein the bodies of the primary dimension column and the secondary dimension column as well as part of the three-way tube are arranged inside a heating oven, and the two-position three-way valve is arranged outside the heating oven;

[0033] Step 2. Controlling the valve core of the two-position three-way valve such that the gas inlet of the two-position three-way valve is in communication with a second gas outlet other than the first gas outlet for a first predetermined time t.sub.fill during which the sample after primary dimension separation flows into the third branch of the three-way tube with the carrier gas, wherein the first predetermined time t.sub.fill is set such that the sample after primary dimension separation flows with the carrier gas only into a portion of the third branch of the three-way tube that is located inside the heating oven without flowing into any portion of the third branch of the three-way tube that is located outside the heating oven.

[0034] Step 3. After the end of Step 2, controlling the valve core of the two-position three-way valve such that the gas inlet of the two-position three-way valve is in communication with the first gas outlet other than the second gas outlet for a second predetermined time t.sub.flush during which the carrier gas comes in from the first gas outlet and carries the sample present in the third branch of the three-way tube into the secondary dimension column for orthogonal separation, wherein during the t.sub.flush, only the sample present in the third branch of the three-way tube flows into the secondary dimension column for orthogonal separation and then into the detector for detection, and also during the t.sub.flush: the end-to-end pressure between the first end and the second end of the primary dimension column is temporarily balanced and thus the flow of sample in the primary dimension column is stopped without further sample separation; or the pressure at the first end of the primary dimension column is slightly higher than that at the second end and thus results in a slow sample separation in the primary dimension column.

[0035] Step 4. Restarting Step 2 after the end of Step 3.