Switching compensation method of low-pressure gradient valve in ultrahigh-pressure pump environment

Abstract

The invention discloses a switching compensation method of a low-pressure gradient valve in an ultrahigh-pressure pump environment, which comprises the following steps of: acquiring a volume to be compensated of a solution; after the ultrahigh pressure pump sucks the solution with the set volume, the solution with the volume to be compensated is continuously sucked. In the liquid conveying process of the ultrahigh pressure pump, compensation is conducted on the ultrahigh pressure pump, and therefore the liquid conveying precision of the ultrahigh pressure pump is improved.

Description

Technical Field

[0001] The invention relates to a liquid chromatography pump infusion technology, and in particular to a switching compensation method for a low-pressure gradient valve in an ultra-high-pressure pump environment. Background Art

[0002] The principle of constant-flow infusion of an ultra-high pressure infusion pump is generally to use two sets of linear motors or cam drive mechanisms to drive the plunger rods of the two pump heads to make them perform alternating uniform linear motion. Generally, when aspirating liquid, the plunger rod retreats in an ascending curve, and when pushing liquid, the plunger rod returns in a descending curve during the process of aspirating and pushing liquid. The two pump heads are respectively called the main pump head and the auxiliary pump head. The main and auxiliary pump heads can achieve zero-pulse fluctuation constant-flow infusion by connecting them in series and parallel.

[0003] The main and auxiliary pumps suck liquid alternately. Before the main pump starts to suck liquid, it is generally believed that the solvent pressure in the main pump is close to the system pressure. At this time, as the main pump starts to suck liquid, the solvent pressure of the main pump is first "decompressed", and the pressure will gradually release to atmospheric pressure, that is, normal pressure. We call this process the "decompression process". During the decompression process, the main pump does not actually perform a real suction operation, so when switching the gradient valve, the decompression factor should be considered first.

[0004] However, under the conditions of ultra-high pressure and micro-flow (such as flow below microliter), only considering the "decompression process" is often no longer accurate and will introduce large errors. Therefore, a pressure sensor is generally added between the main pump and the auxiliary pump to directly detect the pressure of the main pump. When the detected pressure is close to normal pressure, the decompression process is considered to be completed, that is, the actual liquid suction process begins from this point, and instructions are sent to the motor from this point to perform low-pressure gradient valve switching calculations. However, in actual applications, liquid suction does not begin when the pressure is released to atmospheric pressure, because the actual starting point of infusion is actually the opening of the one-way valve, and the moment when the liquid begins to enter the pump cavity is the starting point of infusion.

[0005] The opening of the one-way valve actually requires a negative pressure, that is, the plunger of the main pump enters the liquid suction cycle, and the liquid pressure in the pump chamber gradually drops from high pressure to normal pressure, and the normal pressure becomes negative pressure. The negative pressure generates a thrust to open the gem ball of the one-way valve before infusion. Then when the one-way valve is closed, the ball falls, causing part of the liquid to be squeezed out in front of the valve, which will produce a certain dead volume, thereby reducing the infusion accuracy of the ultra-high pressure pump. Summary of the invention

[0006] In order to solve the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a switching compensation method for a low-pressure gradient valve in an ultra-high pressure pump environment, which method can improve the infusion accuracy of the ultra-high pressure pump.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a switching compensation method of a low-pressure gradient valve in an ultra-high-pressure pump environment, comprising the following steps:

[0008] Obtain the volume V0 of the solution to be compensated;

[0009] After the ultrahigh pressure pump sucks the solution of set volume V4, it continues to suck the solution of volume V0;

[0010] Among them, V0=V1+V2;

[0011] V1 is the decompression volume of the ultrahigh pressure pump, V2 is the dead volume before the valve between the gradient valve and the one-way valve, V3 is the volume of the solution actually sucked into the pump by the ultrahigh pressure pump, and k is the fitting slope.

[0012] Optionally, the decompression volume V1 of the ultra-high pressure pump is obtained by an experimental method; and the volume V3 of the solution actually sucked into the ultra-high pressure pump is obtained by a measurement method.

[0013] Optionally, the process of obtaining the dead volume V2 before the valve between the gradient valve and the one-way valve is as follows:

[0014] In the gradient valve, the first channel is used to pass water, the second channel is used to pass 0.1% acetone-water solution, and the volume of the first channel is Va, and the volume of the second channel is Vb;

[0015] The volume ratio of acetone to water solution introduced into the second channel is set to R1, the actual volume ratio of acetone to water solution introduced into the second channel is R2, and the total liquid volume sucked by the ultrahigh pressure pump is V4, wherein Vb = V3*R1;

[0016] When V2 = 0, Where Va+Vb=V3=V4-V1,

[0017] When V2≠0,

[0018] Subtract R2 from R1 and we get

[0019]

[0020] Perform a linear fit between R1 and ΔR to obtain the fitting slope k, and obtain

[0021] By adopting the above technical solution, the present invention compensates the ultra-high pressure pump during the infusion process, thereby improving the infusion accuracy of the ultra-high pressure pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the operating curve of the pump under ideal conditions;

[0023] Figure 2 It is the actual operating curve of the ultra-high pressure pump. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] like Figure 1 The figure shows the operating curve of the pump under ideal conditions. Under ideal conditions, only the "decompression" volume needs to be considered in the operating curve of the pump. Figure 1 The area of ​​the trapezoid of the "decompression process" is integrated, and the integrated area is the decompression volume, recorded as V1. In the actual operation of the pump infusion, due to different solvents, the load back pressure of the pump is different, resulting in different volumes (i.e., V1) released from the pressure to normal pressure during the decompression process. The current mainstream approach is to use a large number of experiments to find certain empirical values, set compensation parameters for different solvents, and use V1 as a fixed value for flow compensation calculation. This method is generally applicable when the back pressure behind the pump is small and the flow rate is large, because under the conditions of small back pressure and large flow rate, the difference between the pressure of the solvent compressed by the pump and the normal pressure is small and the decompression volume V1 is actually very small, so the error is small.

[0027] However, in an ultra-high pressure pump, any slight change will cause a change in the infusion accuracy. Figure 2 As shown, in the operation curve of the ultra-high pressure pump, there is not only the decompression volume V1, but also the dead volume V2 before the valve between the gradient valve and the one-way valve. During the entire liquid suction process of the ultra-high pressure pump, the set total liquid suction volume V4 is fixed. Therefore, after the ultra-high pressure pump sucks the solution with a volume of V4, it is necessary to compensate for the decompression volume V1 and the dead volume V2 before the valve.

[0028] Based on this, the present invention discloses a switching compensation method for a low-pressure gradient valve in an ultra-high pressure pump environment, comprising the following steps:

[0029] Obtain the volume V0 of the solution to be compensated;

[0030] After the ultrahigh pressure pump sucks the solution of set volume V4, it continues to suck the solution of volume V0;

[0031] Among them, V0=V1+V2;

[0032] V1 is the decompression volume of the ultrahigh pressure pump, V2 is the dead volume before the valve between the gradient valve and the one-way valve, V3 is the volume of the solution actually sucked into the pump by the ultrahigh pressure pump, and k is the fitting slope.

[0033] In the above process, the decompression volume V1 of the ultra-high pressure pump is obtained by an experimental method; and the volume V3 of the solution actually sucked into the pump by the ultra-high pressure pump is obtained by a measurement method.

[0034] The process of obtaining the dead volume V2 before the valve between the gradient valve and the one-way valve is as follows:

[0035] In the gradient valve, the first channel is used to pass water, the second channel is used to pass 0.1% acetone-water solution, and the volume of the first channel is Va, and the volume of the second channel is Vb;

[0036] The volume ratio of acetone to water solution introduced into the second channel is set to R1, the actual volume ratio of acetone to water solution introduced into the second channel is R2, and the total liquid volume sucked by the ultrahigh pressure pump is V4, wherein Vb = V3*R1;

[0037] When V2 = 0, Where Va+Vb=V3=V4-V1,

[0038] When V2≠0,

[0039] Subtract R2 from R1 and we get

[0040]

[0041] ΔR is a linear function of R1, so we can use the gradient error test method to perform a gradient method with a fixed gradient change ratio, perform a linear fit between R1 and ΔR, and obtain the fitting slope k, thus obtaining

[0042] Two sets of comparative data are used below to observe the gradient errors of the compensation method of the present invention and the compensation method of the present invention not being used.

[0043] Table 1

[0044]

[0045] Table 2

[0046]

[0047]

[0048] In the above two sets of data, Table 1 is the gradient error data when the compensation method of the present invention is not adopted, and Table 2 is the gradient error data when the compensation method of the present invention is adopted. From the comparison of the two sets of data, it can be concluded that after adopting the compensation method of the present invention, the gradient error is significantly reduced.

[0049] In the above two sets of data, the calculation of each data is carried out in accordance with the standard "JJG705-2014 Liquid Chromatograph Calibration Procedure".

[0050] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0051] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A switching compensation method for a low-pressure gradient valve in an ultra-high-pressure pump environment, characterized in that: The following steps are included: Obtain the volume V0 of the solution to be compensated; After the ultrahigh pressure pump sucks the solution of set volume V4, it continues to suck the solution of volume V0; Among them, V0=V1+V2; V1 is the decompression volume of the ultrahigh pressure pump, V2 is the dead volume before the valve between the gradient valve and the one-way valve, V3 is the volume of the solution actually sucked into the pump by the ultrahigh pressure pump, and k is the fitting slope.

2. The switching compensation method of the low-pressure gradient valve in an ultra-high pressure pump environment according to claim 1, characterized in that: The decompression volume V1 of the ultra-high pressure pump is obtained by experimental method; the volume V3 of the solution actually sucked into the pump by the ultra-high pressure pump is obtained by measurement method.

3. The switching compensation method of the low-pressure gradient valve in an ultra-high pressure pump environment according to claim 2, characterized in that: The process of obtaining the dead volume V2 before the valve between the gradient valve and the one-way valve is as follows: In the gradient valve, the first channel is used to pass water, the second channel is used to pass 0.1% acetone-water solution, and the volume of the first channel is Va, and the volume of the second channel is Vb; The volume ratio of acetone to water solution introduced into the second channel is set to R1, the actual volume ratio of acetone to water solution introduced into the second channel is R2, and the total liquid volume sucked by the ultrahigh pressure pump is V4, wherein Vb = V3*R1; When V2 = 0, Where Va+Vb=V3=V4-V1, When V2≠0, Subtract R2 from R1 and we get Perform a linear fit between R1 and ΔR to obtain the fitting slope k, and obtain

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