JPH0324625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid chromatograph, and more particularly to a liquid chromatograph equipped with a liquid feeding section, a sample injection section, a separation section, and a detection section.

The liquid feeding section includes a liquid feeding section, a sample injection section, a separation section, and a detection section, and the liquid feeding section includes a plurality of eluent reservoirs in which a predetermined eluent is stored, and a solenoid valve connected to each of these eluent reservoirs. A liquid chromatograph consists of a pump having a pump chamber connected to these electromagnetic valves via a check valve on the suction side and having a check valve on the discharge side. When performing the so-called gradient elution method in which the composition of the eluent is continuously changed, there are the following problems, and special equipment is required to solve them.

That is, for example, when water and methanol are selected as eluents and a gradient elution method from water to methanol is performed, bubbles are generated due to the mixing of water and methanol. When these air bubbles are sucked into the pump, in the case of liquid chromatographs that use reciprocating pumps, they can cause the pump's check valve to malfunction, causing irregular flow of liquid from the sample injection section to the separation section. This causes fluctuations in the baseline of the detector, which is the detection unit, and poor reproducibility of the chromatogram. This is a fatal flaw for liquid chromatographs. Bubbles are generated by mixing the eluent water and an organic solvent because the solubility of the organic solvent in air is greater than the solubility of water in air, and by mixing the two, the mixed eluent is less resistant to air. Since the solubility is lower than that of the organic solvent, the air dissolved in the organic solvent becomes supersaturated and bubbles are generated. Therefore, if the air in the organic solvent is removed in advance, the generation of bubbles during mixing can be prevented. However, even if you take the pains to degas it, if the liquid surface is in contact with air, the air will immediately dissolve, so it will not be very effective. The most effective method in this regard is to continuously bubble helium gas, which has low solubility, into an organic solvent, but this method requires special equipment such as gas piping and gas bubbling equipment. This complicates the equipment and poses a risk of evaporation of the solvent along with bubbling of helium gas. Furthermore, when a mixed solvent is used as the solvent, there is a concern that the composition may change due to evaporation of the solvent.

The present invention has been made in view of the above points,
The purpose is to provide a liquid chromatograph in which liquid can be smoothly transferred even when using a solvent system that generates bubbles during mixing.

That is, the present invention provides a first suction side check valve connected to a first eluent reservoir through a flow path, and a second suction side check valve connected to a second eluent reservoir through another flow path. The pump is characterized in that a side check valve is provided, and the first and second suction side check valves are connected so as to communicate with a pump chamber of the pump.

The present invention was achieved as a result of studies on the generation of air bubbles and the effects of the generated air bubbles on check valves. The generation of bubbles is explained in Figure 1, which shows the relationship between the solvent polarity index of various solvents and the solubility of air, with the horizontal axis representing the solvent polarity index and the vertical axis representing the solubility of air. It depends on the type of solvent to be mixed. As shown in the figure, the solubility of a solvent in air varies depending on the type of solvent. Generally, the lower the polarity of the solvent, the higher the solubility of air. For example, the solubility of organic solvents such as hexane and methanol in air is higher. ,
That of water is about 1/10 to 1/100 compared to organic solvents.
And small. When solvents with a large difference in solubility for air, such as water and methanol, are mixed, bubbles are generated, and even when solvents with a small difference in solubility for air, for example, ethanol and methanol are mixed, there are almost no bubbles. Does not occur. In other words, bubbles are generated when water is mixed with a so-called polar organic solvent such as methanol, which is most commonly used in this type of liquid chromatograph, and bubbles are almost always generated when organic solvents or aqueous solutions are mixed. It was confirmed that it did not.

This malfunction of the check valve due to air bubbles is caused by the malfunction of the check valve 1 on the suction side of the pump, as shown in FIG. That is, as shown in the figure, a plunger 3 and a suction side check valve 1 are driven by a cam 2 and move back and forth as indicated by arrows at both ends in the figure.
By working with the discharge-side check valve 4, suction and discharge operations of the mixed eluent P are repeated as indicated by arrows in the figure, and the liquid is fed. When the plunger 3 moves to the right in the figure, the suction side check valve 1 opens, the discharge side check valve 4 closes, and the mixed eluent P is sucked into the pump chamber 5. When the plunger 3 moves to the left in the figure, the eluent mixture P is sucked into the pump chamber 5. The suction side check valve 1 is closed, the discharge side check valve 4 is opened, and the mixed eluent P is discharged from the pump chamber 5. In this case, if the check valves 1 and 4 are opened and closed reliably, the mixed eluent P can be stably fed, but the bubbles 6
When the air bubbles 6 are sucked in, the air bubbles 6 stagnate between the ball 7 and the valve seat 8 that make up the suction side check valve 1, and prevent the ball 7 from coming into close contact with the valve seat 8, so that the pump enters the discharge stroke. If this happens, the mixed eluent P will flow backwards from the suction side check valve 1, making the liquid feeding unstable.

By the way, even if the air bubbles 6 are inhaled, if the air bubbles 6 pass through the suction side check valve 1 and enter the pump chamber 5, the suction side check valve 1 will surely close during the discharge stroke.
The inside of the pump chamber 5 is pressurized, and the bubbles 6 are mixed with the eluent P.
It is dissolved and discharged. Therefore, the air bubbles 6 that enter the pump chamber 5 do not have any adverse effect on the operation of the check valves 1 and 4, so even if a solvent system that generates air bubbles during mixing is used, the air bubbles 6 cannot be mixed in the pump chamber 5. death,
It has been confirmed that it is sufficient to generate bubbles within the pump chamber 5. Therefore, in the present invention, the first
a first suction side check valve connected to the eluent reservoir through a flow path, and a second suction side check valve connected to the second eluent reservoir through another flow path, The first and second suction side check valves were connected to communicate with the pump chamber of the pump. By doing so, it is possible to obtain a liquid chromatograph in which liquid feeding is performed smoothly even when using a solvent system that generates air bubbles during mixing.

Examples in which the present invention is applied to a liquid chromatograph will be described below. One embodiment is shown in FIGS. 3 and 4. Note that the second
Components that are the same as those in the figures are given the same reference numerals, and therefore their explanations will be omitted. Pump 11 of liquid feeding section 14 in FIG.
includes the cam 2, plunger 3, discharge side check valve 4, pump chamber 5, check valves 1a and 1b, and pressure sensor 13 in FIG. In this embodiment, at least two check valves 1a and 1b on the suction side are provided so as to correspond to each eluent, and predetermined eluents A and B are mixed in the chamber 5 of the pump. By doing so, bubbles are generated within the pump chamber 5, and a liquid chromatograph in which liquid can be smoothly delivered can be obtained.

That is, eluent reservoirs 9a and 9b in which predetermined eluents A and B are stored, and these eluent reservoirs 9a and 9.
Solenoid valves 10a and 10b respectively connected to
The pump 11 is connected to the pump chamber 5 via these electromagnetic valves 10a, 10b and at least two suction side check valves 1a, 1b, and the eluent A,
Since the eluent B is mixed, the eluent A in the eluent reservoir 9a is sucked into the pump chamber 5 from the solenoid valve 10a via the suction side check valve 1a, and the eluent B in the eluent reservoir 9b is sucked into the pump chamber 5 through the solenoid valve 10a. The eluents A and B are then mixed in the pump chamber 5, and bubbles are generated in the pump chamber 5, causing the suction Side check valve 1
Malfunctions of a and 1b can be prevented. The mixing ratio of eluents A and B is determined by the solenoid valves 10a and 10b.
The control device 12 alternately opens and closes the opening and closing times.
The mixing ratio can be changed by controlling the mixing ratio, and an arbitrary mixing ratio can be obtained. Then, the bubbles generated in the pump chamber 5 are pressurized and dissolved in the mixed eluent, but
While the generated bubbles are being compressed and dissolved, the ejection of the mixed eluent is interrupted and the flow rate is reduced. This can be solved as follows. The pressure sensor 13 detects the drop in pressure when the discharge is interrupted, and the cam 2
is rotated rapidly to instantly compress the air bubbles. After the bubbles disappear, discharge starts and the pressure increases, so the pressure is detected by the pressure sensor 13 and the cam 2
Return it to normal rotation speed. In this way, the mixed eluent can be smoothly discharged, and the discharge of the mixed eluent can be prevented from being interrupted. In addition, in FIG. 3, 14 is a liquid feeding part, 15
1 is a sample injection section, 16 is a separation section (column), and 17 is a detection section (detector).

Another embodiment of the invention is shown in FIG. In this example, three kinds of eluents A, B, and C are used, and three suction side check valves 1a, 1b,
1c was provided to mix the eluents A, B, and C within the pump chamber 5. In this case, the eluent A is supplied from the suction side check valve 1a, and the eluent B is supplied from the suction side check valve 1a.
From b, the eluent C is sucked into the pump chamber 5 from the suction side check valve 1c, and these eluents A, B, and C are mixed in the pump chamber 5, as in the previous case. It is possible to achieve the following effects.
In the figure, 9c is an eluent reservoir for storing the eluent C, and 10c is a solenoid valve.

FIG. 6 shows yet another embodiment of the invention. In this example, three types of eluents A, B, and C are used, and two suction side check valves 1a and 1b are used.
was provided so that the eluents A, B, and C were mixed in the pump chamber 5. In this case, the eluent A is sucked into the pump chamber 5 from the suction side check valve 1a, and the eluents B and C are mixed in advance and then sucked into the pump chamber 5 from the suction side check valve 1b. Since the mixed liquids A, B, and C are mixed, the number of suction side check valves can be reduced by one compared to the above case.

That is, when three types of eluents A, B, and C are used, one of the three types of eluents A, B, and C is
is an organic solvent and the other two B and C are aqueous solutions, or one A is an aqueous solution and the other two B and C
However, as mentioned above, mixing organic solvents or aqueous solutions hardly generates bubbles, so organic solvents B and C or aqueous solutions B and C should be mixed in advance. After that, the suction side check valve 1b is passed through.

As described above, in the present invention, at least two check valves on the suction side are provided and the eluent is mixed in the pump chamber, so that air bubbles are generated in the pump chamber and malfunction of the check valve on the suction side due to air bubbles is prevented. This makes it possible to obtain a liquid chromatograph in which liquid feeding is performed smoothly even when using a solvent system that generates air bubbles during mixing.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the relationship between the solvent polarity index of various solvents and the solubility of air, Fig. 2 is an explanatory diagram illustrating the influence of air bubbles during liquid transfer in a liquid chromatograph,
Fig. 3 is a block diagram of an embodiment of the liquid chromatograph of the present invention, Fig. 4 is a block diagram of a liquid feeding section of an embodiment of the liquid chromatograph of the present invention, and Fig. 5 is a block diagram of the liquid chromatograph of the present invention. Fig. 6 is a block diagram of a liquid sending section of still another embodiment of the liquid chromatograph of the present invention. 1a, 1b, 1c...Suction side check valve, 4...Discharge side check valve, 5...Pump chamber, 9a, 9b, 9c...Eluent reservoir, 10a, 10b, 10c...Solenoid valve, 14...
Liquid feeding section, 15... Sample injection section, 16... Separation section, 17
...detection section, A, B, C... eluent.

Claims (1)

[Claims] 1. In a liquid chromatograph in which an eluent is sent to a separation section by a reciprocating pump, a first suction-side check valve and a second eluent are connected to a first eluent reservoir via a flow path. A second suction side check valve connected to the liquid reservoir via another flow path is provided, and the first and second suction side check valves are connected so as to communicate with the pump chamber of the pump. Characteristic liquid chromatograph.