JPH05256834A - Liquid chromatograph - Google Patents

Abstract

PURPOSE:To obtain the liquid chromatograph in which the damage of columns is prevented by reducing pressure shocks given to the columns due to the rise in pressure at the time of sample injection. CONSTITUTION:A control section 3 has a constant flow rate control function 10 and constant pressure control function 11 so that the section 3 can use either one of the functions by switching. During normal operations, accurate analyses are performed by using the function 10. When a flow passage is closed due to the switching of an injection valve 5, or the like, a pump 1 is controlled so that the exit-side pressure of the pump 1 detected by means of a pressure detector 2 can become constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid chromatograph, and more particularly to a liquid chromatograph suitable for preventing column damage by reducing a pressure shock due to a pressure increase during sample injection.

[0002]

2. Description of the Related Art The structure of a general liquid chromatograph is shown in FIG. The eluent aspirated by the pump is
It flows through the column and the detector. The sample is injected into the flow channel by the injection valve of the sample injection unit and separated by the column.
The separated component is detected by the detector and the signal is sent to the data processing device. The data processing result is output as the analysis result.

The principle of a typical sample injection part is shown in FIG.
The following operation is performed in order to inject the sample into the channel in which the high-pressure liquid is flowing. Initially, the injection valve 5 is set as shown in (a), and the eluent 4 is passed through the sample loop 6 and the column 9 by the pump 1.
Is flowing to. Next, as shown in (b), the injection valve 5
And the sample suction pump 8 is operated to suck the sample into the sample loop 6. After that, the injection valve 5 is returned to the state of (a) again, and the sample is injected into the high-pressure channel.

In the conventional liquid chromatograph, the pump was sending liquid at a constant flow rate even while the injection valve was being switched. When switching the injection valve, there is a state in which the flow path system is closed as shown in FIG. In this state, the pump continues to feed the liquid, so the pressure in the flow path before the valve rises. After that, when the valve switching was completed, the increased pressure was applied to the column, which could damage the column. In addition, since the pressure on the outlet side of the pump becomes high, when the pump is used near the maximum working pressure, the pressure limit may be exceeded during sample injection, and the pump may stop operating, such as sugar.

In order to cope with this, in the conventional liquid chromatograph, a bypass flow passage 12 is provided in the injection valve portion as shown in FIG. 5, or a damper 13 as shown in FIG.
Was placed in the flow path between the pump and the injection valve.

[0006]

Of the above-mentioned conventional techniques,
The method using the bypass flow passage does not consider the error due to the liquid flowing in the bypass and the point of sample diffusion, and it is difficult to make the bypass flow passage inner diameter constant.
There was a problem that the operation was unstable. Further, the damper method has a problem that it causes an error when a gradient device is attached.

An object of the present invention is to provide a liquid chromatograph which does not have these problems.

[0008]

In order to achieve the above object, both constant flow rate control and constant pressure control are provided, and while the flow path is closed, such as when switching the injection valve, the pump outlet side The pump is controlled at a constant pressure so that the pressure becomes constant. When the flow path is not closed, the flow rate is controlled to be constant so that an accurate chromatograph can be obtained. Further, when switching to the constant pressure control, the pressure is controlled so as to be the pressure at the constant flow rate control so that the pressure fluctuation during that time does not occur.

[0009]

By maintaining the pressure of the pump constant, the pressure fluctuation applied to the column when the injection valve is switched can be reduced, and the column can be prevented from being damaged. Further, since there is no bypass channel or damper, there is no sample dilution or gradient error due to it.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of this embodiment. The eluent 4 sucked by the pump 1 is sent to the column 9 through the injection valve 5. For sample 7, once the injection valve 5 has been switched,
The sample pump 8 sucks into the sample loop 6. Then, the injection valve 5 is switched again to inject the sample into the high-pressure channel.

In the present invention, the control unit 3 is provided with a constant flow rate control function 10 and a constant pressure control function 11 so that both can be arbitrarily switched and used.

In the constant flow rate control, the motor of the pump is rotated at a constant speed except that the operating speed is temporarily changed at the time of shifting from the solvent suction process to the discharge process to correct the pressure change due to the solvent compression. A constant flow rate of liquid has been achieved. Therefore, even if the composition of the solution to be sent changes or the resistance of the flow path changes, constant quantity solution can be sent.

On the other hand, in the constant pressure control, the pump 1 is controlled by continuously changing the liquid supply amount so that the pressure at the pump outlet detected by the pressure detector 2 becomes constant. When the composition of the solution to be sent is constant and the flow path resistance does not change,
This method can also deliver a constant flow rate.

During normal operation, constant flow rate control is performed to send the eluent at a constant flow rate without being affected by changes in the solution composition, thereby performing highly reproducible and accurate analysis. While the injection valve 5 is switched, the flow path is closed, so that the pump 1 is controlled at a constant pressure. At this time, the constant pressure control is performed so as to be the pressure at the constant flow rate control. Therefore, a constant flow rate is maintained except when the flow passage is closed by the valve operation, and pressure fluctuation does not occur even when the flow passage is closed during this period.

FIG. 7 shows a synchronization example of switching of control methods of a typical sample injection part and pump. The switching of the pump control system is in synchronism with the operation of the sample injection part, and constant pressure control is always performed when the valves are switched with the closing of the flow path. Therefore, the pressure does not rise. Further, the liquid is fed at a constant flow rate for most of the time, and a constant flow rate can be maintained without being affected by the change in the composition of the solution to be fed or the change in the flow path resistance due to the deterioration of the column.

FIG. 8 shows the flow of the operation of each part in the actual analysis. Liquid is sent by constant flow rate control to stabilize the system, and the pressure at this time is read. Next, switching to the constant pressure control by this stable pressure is continued and liquid feeding is continued.
After this, the sample injection unit switches the injection valve to the load side and sucks the sample into the sample loop. Next, the injection valve is switched to the injection side to inject the sample into the high-pressure channel, and at the same time, analysis such as the start of a solution gradient or the acquisition of data is started. At this time, since the pump is a constant pressure liquid feed, the pressure does not increase due to the closing of the flow path. After that, the pump is promptly changed to the constant flow rate control, and the actual analysis is performed under the constant flow rate control condition. Therefore, even if the composition of the solution to be transferred changes, accurate quantitative solution transfer can be performed and high reproducibility can be obtained.

According to this embodiment, the pressure does not increase due to the passage being closed while the injection valve 5 is being switched. Therefore, the sample can be injected without damaging the column and at a pressure close to the maximum usable pressure of the pump. Furthermore, there is no occurrence of sample dilution or error as in the method using the bypass channel. Further, since the volume between the pump and the column is not increased by the damper, no error occurs when using the gradient device.

[0018]

EFFECTS OF THE INVENTION According to the present invention, there is an effect that a pressure increase at the time of switching an injection valve is eliminated and a liquid chromatograph free from flow rate error at the time of analysis can be obtained.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a general liquid chromatograph.

FIG. 3 is a principle diagram of a sample injection unit.

FIG. 4 is a diagram showing a flow path closed state.

FIG. 5 is a bypass flow channel system diagram.

FIG. 6 is a damper system diagram.

FIG. 7 is a diagram showing an example of synchronizing the sample injection unit and pump control switching.

FIG. 8 is a diagram showing a flow of operation of each unit at the time of analysis.

[Explanation of symbols]

1 ... Pump, 2 ... Pressure detector, 3 ... Control part, 4 ... Eluent, 5 ... Injection valve, 6 ... Sample loop, 7 ... Sample,
8 ... Sample pump, 9 ... Column, 10 ... Constant flow rate control function, 11 ... Constant pressure control function, 12 ... Bypass flow path, 13 ...
Damper.

Claims (2)

[Claims] 1. A liquid chromatograph equipped with a pump, a sample injection section including an injection valve, and a column, and a constant flow rate control function for making constant the flow rate on the outlet side of the pump by intermittently changing the motor operating speed, and a continuous flow rate control function. A control unit that has a constant pressure control function that keeps the pressure on the outlet side of the pump constant by changing the motor operating speed is provided, and both of these controls can be switched arbitrarily, and when switching from constant flow rate control to constant pressure control A liquid chromatograph characterized in that control is performed so as to obtain a pressure at the time of control. 2. The liquid chromatograph according to claim 1,
A liquid chromatograph characterized in that switching between the above two controls is performed in synchronization with switching of an injection valve of a sample injection unit.