JPH02238358A - Method for controlling solvent composition in liquid chromatograph - Google Patents

Abstract

PURPOSE:To control the composition of a solvent highly accurately and precisely and to improve the gradient accuracy in liquid chromatograph by switching control valves based on the non-intake cycle of a liquid feeding pump. CONSTITUTION:Solvents A, B, C and D are arranged in the order of low concentrations. At a starting time point To, the solvent A is switched to B. The intake starting time point immediately after the start is T1. The solvent is changed from B to A during an intake cycle with a pump head P1. A time point T2 is obtained by experiment. The solvent is changed from A to C at the intermediate point of the non-intake cycle immediately after T2. The intake starting time point by the pump head P2 immediately after said switching is T3. The solvent is changed from C to A during the intake cycle. Thereafter, the switching time is obtained by the same way, and control valves 8a, 8b, 8c and 8d are switched. Thus, one period is finished. The concentration accuracy can be made accurate by repeating this procedure.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for controlling solvent composition when a mixed solution of multiple types of solvents is used as a mobile phase, such as in gradient analysis, in analysis using liquid chromatography. (Prior art) As a method of mixing multiple solvents, a plurality of solvent tanks are connected to the inlet of a liquid pump through control valves, and the control valves are sequentially opened and closed to control the liquid feeding pump. Each solvent is supplied at a predetermined ratio to the pump. Switching of the control valve is performed only during the suction process of the liquid pump, and the control valve is switched at the same time as the suction process starts, and the control valve is switched at the same time as the suction process starts. When the control valve operating time corresponding to the set concentration of the solvent that is open is reached, the control valve is switched to close.

(Problems to be Solved by the Invention) In order to improve the accuracy and precision of solvent composition, it is necessary to temporarily close all control valves when switching control valves. When the control valve is switched at the beginning of the suction process and then switched again during that process, the concentration of solvent supplied by the control valve is low, and for example, the time the control valve is kept open is about several hundred milliseconds. In the case of such a short time, the error in the amount of solvent sucked into the liquid pump becomes large.

An object of the present invention is to provide a method for controlling the composition of a solvent that allows accurate inhalation even when a solvent with low concentration components is inhaled.

(Means for Solving the Problems) Conventionally, the control valves were switched at the beginning of the suction process, but in the present invention, the control valves are switched during the non-suction cycle.

Further, in the present invention, the control valve is not switched more than once during one suction stroke.

(Function) Switching the control valve during the first short period of the suction process of the liquid transfer pump increases the error, but in the present invention, the control valve is already switched during the non-suction cycle, and the control valve is switched during the first short period of the suction process of the liquid pump. Minimize control valve switching over time as much as possible.

When the control valve is opened during a non-inhalation cycle and the solvent is switched during the immediately following suction process, the control valve must be opened in the middle of the suction process to avoid switching the control valve again during the remainder of the suction process. The control valves are switched so that the control valve for the solvent with a high concentration component is opened. If the control valve is switched only once during one suction process, it is possible to determine the exact amount of solvent by experimentally determining the relationship between the time from the start of the suction process to the time when the control valve is switched and the suction amount. becomes easier to inhale.

(Example) FIG. 1 shows an example of the present invention in which four types of solvents are mixed at an arbitrary ratio and supplied to a liquid chromatograph.

2 is a liquid sending pump, which has two pump heads P1 and P2.
It is equipped with Each pump head PL, P2 is a type of pump that pumps liquid by reciprocating the plunger, and each pump head P1, P2 is equipped with a check valve 4 on the inflow side and a check valve 6 on the outflow side. We are prepared. On the inflow side of the pump 2, solvent tanks for four types of solvents A, B, C, and D are connected to control valves 8a, 8b, . They are connected via 8c and 8d. A liquid chromatograph 12 is connected to the outlet side of the pump 2 via a mixer 10 that mixes the pumped solvent.

14 is a control means, 16 is a setting means, and the control means 14
is the pump head P according to the flow rate set by the setting means 16.
L and P2 are activated, and at the same time, control valves 8a, 8b, 8c, and 8d are switched based on the control valve switching timing calculated based on the set mixture ratio and the rotational state of pump heads PL and P2.

Next, the operation of this embodiment will be explained. As an example,
The proportions of solvents A, B, C, and D were 47% and 10%, respectively.
Fig. 2 shows the control valve switching timing when the ratio is 13% and 30%, and Fig. 3 shows the algorithm at that time.

Solvents A, B, C, and D are arranged in descending order of concentration (step Sl
). B, C, D, A.

At the start time To, the solvent A is switched to B (step S2).6 The start time To is the midpoint of the non-inhalation cycle.

The inhalation start point immediately after the start is T1. The solvent is switched from B to A during the suction cycle by pump head P1 (step S3). The switching time T2 is determined by T2=Ti+F (B). Here, F (X) is a function that provides the optimum control valve operating time for the set concentration, and is determined by experiment. .

At the midpoint of the non-inhalation cycle immediately after T2, solvent A is switched to C (step S4). Immediately after that, the pump head P2 starts suctioning at T3. Switch from solvent C to A during the inhalation cycle. The switching time T4 is determined by T4=730F (C) (step S5).

Thereafter, while determining the switching time in the same manner, the control valve 8a
, 8b, 8c, and 8d.

When one cycle of switching of the four control valves 8a, 8b, 8c, and 8d is completed, the control valves 8a. The switching control of 8b, 8c, and 8d is repeated.

If the same concentration of mobile phase is used in the next cycle, the second
Repeat the same cycle as shown in the diagram.

In addition, when making the concentrations different, each control valve 8a, 8b, 8c according to the concentration program set in the setting means 16.
, 8d are calculated and the control valves are switched in the same manner.

Although the embodiments are described using examples in which four types of solvents are mixed, the present invention can be similarly applied even if the number of types of solvents is two, three, or five or more.

As shown in Figure 2, the solvent injected after switching the control valve during the inhalation process is the most yielding solvent (A in this case), so the control valve is injected during one inhalation cycle. This eliminates the need to switch over two or more times, making concentration control more accurate.

(Effects of the Invention) In the present invention, the control valve is not switched at the beginning of the suction process, but is switched during the non-suction cycle, making it possible to control the solvent composition with high accuracy and precision. Improves chromatographic gradient accuracy.

In addition, by determining the control valve switching order according to the concentration of the mixed solvent so that the control valve does not need to be switched more than once during one suction process, solvent composition control with higher accuracy and precision can be achieved. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a solvent mixing apparatus to which the present invention is applied, FIG. 2 is a diagram showing a solvent suction cycle in one embodiment, and FIG. 3 is a flowchart diagram showing one embodiment. 2...Liquid pump, PL, P2...Pump head, 12...Liquid chromatograph, 1
4...Control means, 1 6--Setting means, 8a
, 8b, 8c, 8d... control valve, A, B, C,
D...Solvent. Patent applicant: Shimadzu Corporation

Claims (2)

[Claims] (1) Connect multiple solvent tanks to the inlet of the liquid chromatograph's liquid pump through control valves, and sequentially open and close the control valves to supply each solvent to the liquid pump at a predetermined ratio. A method for controlling a solvent structure, characterized in that the supplying method includes switching a control valve during a non-inhalation cycle of a liquid feeding pump. (2) The solvent composition control method according to claim 1, wherein the control valve is not switched more than once during one suction step of the liquid pump.