JPH0291563A - Supercritical fluid chromatograph - Google Patents

Abstract

PURPOSE:To prevent the generation of the deposition of a sample component near a column outlet arising from the pressure drop of a column by connecting a pressurizing means to the flow passage of the column outlet. CONSTITUTION:Fluid 11 for pressure regulation is joined to a part 9 of the flow passage on the downstream side of the column from a pump 10 for pressurization. While materials such as carbon dioxide, ammonia and nitrogen are usable for the fluid 11 for pressure regulation, the same material as the material of moving phase fluid is preferably used. Both of a pump 2 for the moving phase and the pump 10 for pressurization are pumps of a constant pressure control system and are controlled by a pump control section 13 which takes in the signals of pressure sensors 8, 12. The inside of the flow passage near the column outlet is maintained under a high pressure in this way and the deposition of the sample component near the column outlet is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a supercritical fluid chromatograph (hereinafter referred to as "5FCJ").

(Prior art) In conventional SFC, a flow path resistance is installed downstream of the column, and the mobile phase is pumped under pressure by a fluid pump upstream of the column.
A supercritical state is created in the flow path from the pump outlet to the inside of the column. FIG. 3 is a flow path diagram showing a conventional SFC. In FIG. 3, reference numeral 1 denotes a cylinder containing a mobile phase, and the mobile phase in the cylinder is sent to a column 4 through a sample inlet 3 by a mobile phase pump 2. 5 is a column constant temperature bath, and column 4 is kept at constant temperature. In the figure, 6 is a resistance tube, and a capillary tube with an inner diameter of several micrometers is used. 7 is a detector. The mobile phase pump 2 moves against the flow path resistance of the resistance tube 6. Since the phase is pumped, pump 2.
Sample introduction port 3. The mobile phase between the column 4 and the resistance tube 6 is maintained in a supercritical state.

(Problem to be solved by the invention) The column used in SFC acts as a resistance in the flow path.

Therefore, a pressure drop occurs within the column, and the pressure is considerably lower near the column outlet than at the column inlet.

Carbon dioxide is usually used as the mobile phase in SFC, but the solubility of a chemical substance in carbon dioxide increases as the density of the mobile phase fluid increases, so the density of the mobile phase fluid decreases near the column outlet where the pressure is low. As a result, the sample components cannot be completely dissolved and precipitate, resulting in the sample components not being carried to the detector and not being detected. Furthermore, if the precipitated sample components accumulate in the column and the column becomes clogged, it may cause deterioration. Although increasing the inlet pressure increases the pressure at the column outlet, it is not possible to increase the inlet pressure beyond the column operating pressure angle range.

The object of the present invention is to obtain an SFC that does not cause precipitation of sample components near the column outlet due to column pressure drop.

(Means for Solving the Problems) In the supercritical fluid chromatograph of the present invention, a pressurizing means is connected to the column outlet flow path.In the present invention, the pressurizing means is a pump, or a column inlet side and a column outlet side. Includes a resistance tube that connects the

(Function) In the SFC of the present invention, the column outlet channel is forcibly pressurized. Since the column inlet pressure is controlled by the liquid feeding pressure of the mobile phase pump, the pressure drop within the column is reduced by pressurizing the outlet side. Due to the load on the pressurizing means, a state occurs in which the pressure on the column outlet side is increased by the amount of pressure applied. On the other hand, since the density of the mobile phase fluid depends on the absolute value of the pressure, the density of the mobile phase fluid increases by the amount that the pressure is increased, and the solubility of the chemical substance in the mobile phase increases.

(Example) FIG. 1 is a flow path diagram of an SFC that is an example of the present invention. The conventional SFC components shown in Fig. 3 are the SFC components in Fig. 1.
Components similar to those of the FC are given the same numbers. Reference numeral 9 in FIG. 1 is a part of the flow path on the downstream side of the column, into which the pressure adjusting fluid 11 is merged from the pressurizing pump 10. For the pressure adjustment fluid 11, substances such as carbon dioxide, ammonia, and nitrogen can be used, but it is preferable to use the same substance as the mobile phase fluid.Both the mobile phase pump 2 and the pressurization pump 10 are constant pressure control type pumps. It is controlled by a pump control section 13 which receives signals from pressure sensors 8 and 12.

Furthermore, during analysis using the pressure programming method, which is an analysis method that changes the pressure during one analysis, the pump control unit 13 controls the mobile phase pump 2 according to the program and also takes in the signals of the pressure sensors 8 and 12.

The pressurizing pump 10 is controlled so that the difference between the two becomes equal. Alternatively, the pressurizing pump 10 may not be operated until just before the end of the pressure programming method analysis, and after the liquid delivery pressure of the mobile phase pump has reached the final pressure of the program, the pressurizing pump may be operated just before the end of the analysis to close the outlet side. By performing a series of pump operations to apply pressure, the sample components can be optimally separated and then the poorly soluble components can be expelled. FIG. 2 is a flow path diagram of an SFC that is another embodiment of the present invention. Components of the flow path in FIG. 2 that are similar to those of the conventional SFC shown in FIG. 3 are given the same numbers. Reference numeral 14 in FIG. 2 is a resistance tube that connects both the upstream portion of the sample introduction port 3 and the column downstream flow path. As this resistance tube 14, a tube having a resistance smaller than the flow path resistance of the column 4 is selected.

(Effects of the Invention) In the SFC of the present invention, the inside of the flow path near the column outlet is also maintained at a high pressure, so that precipitation of sample components near the column outlet is prevented. For this reason, relatively long backed columns with large pressure drops can also be used. Furthermore, in an embodiment of the present invention using a pressurizing pump, the flow rate within the column can be maintained at an optimal constant value even during pressure programming analysis.

[Brief explanation of the drawing]

FIG. 1 is a flow path diagram of a supercritical fluid chromatograph that is an embodiment of the present invention, and FIG. 2 is a flow path diagram of a supercritical fluid chromatograph that is another embodiment of the present invention. FIG. 3 is a flow path diagram showing a conventional supercritical fluid chromatograph. In the figure, 1 is a mobile phase cylinder, and 2 is a mobile phase pump. 4 is a column, 6 is a resistance tube, and 10 is a pressurizing pump. 14 is a resistance tube. Patent applicant: Shimadzu Corporation

Claims (1)

[Claims] A supercritical fluid chromatograph with a pressurizing means connected to the column outlet channel.