JPH0219426B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement for accurately maintaining the solvent mixture ratio at a set value in a liquid chromatograph that uses two or a mixture of two or more solvents as a developing agent. .

In conventional seed liquid chromatographs, a reciprocating plunger pump is often used as a liquid pump, and two solvents, for example, liquid A and liquid 2, are alternately fed into a solvent mixing chamber, and after mixing are sent to a column analysis system. Although a method of sending liquid is used, there is usually an error between the set value and the actual value of the mixing ratio, and this error will eventually give a measurement error to the liquid chromatograph.

The reason for this mixing ratio error is partly due to the difficulty of completely eliminating the pulsating liquid flow in liquid sending plunger pumps, and also due to the positional displacement of the plunger of the plunger pump and the actual change in flow rate. This is based on the fact that there is a misalignment, and it is also based on the fact that the flow rate fluctuations differ depending on the type of solvent.

This invention aims to eliminate these drawbacks and eliminate the error between the solvent mixture ratio setting value and the actual measurement value.
In a liquid chromatograph that mixes two or more types of solvents and uses one reciprocating plunger pump to send the mixture as a developing agent, there is an electromagnetic opening/closing system between each solvent storage chamber and the solvent mixing chamber. A valve is provided and a solvent mixing ratio measuring section is provided at the subsequent stage, and the suction characteristics are set based on the shape of the cam of the plunger pump etc. and the suction characteristics are assumed from the time displacement of the plunger based on the measured value signal from this measurement mechanism. The present invention relates to a liquid chromatograph solvent mixing apparatus that is provided with a control section that calculates and stores a suction characteristic value determined by actual measurement based on the value, and controls the opening time of the electromagnetic on-off valve based on this suction characteristic value.

The electromagnetic opening/closing valve is selectively opened alternately at a set time ratio for each solvent to be mixed, and each opening is usually completed during one suction stroke of the plunger pump. There are two types of electromagnetic on-off valves: one is to simply control the opening time to change the flow rate, and the other is to change the flow rate by changing the number of opening pulses within a unit time, which is a fixed amount pulse opening method. However, any of these can be applied to the case of this invention.

The control unit for the electromagnetic on-off valve selectively opens and closes the electromagnetic on-off valve for each solvent, and controls the opening time or the number of opening pulses by inputting parameters. Furthermore, it is also possible to control by supplementarily considering the flow velocity coefficient. A commonly used reciprocating plunger pump is driven reciprocatingly by a cam and a spring, and suctions the solvent from the storage chamber and discharges it to the measurement column system. As shown in Figure 3. In other words, the shape of the cam is set so that it becomes an isosceles trapezoid. In the figure, the horizontal axis represents time and the vertical axis represents flow velocity.

As mentioned above, the setting division position of the suction process (2
For example, at the 50% position when the liquids are uniformly mixed, the open components of the electromagnetic switches for the A solvent and the B solvent are switched, so that the A and B liquids are switched at the phase of the A line shown by the dotted line.

In reality, the flow rate of liquid delivery changes from the set value due to the reasons mentioned above, so as shown in Figure 4,
This causes an imbalance in the left and right areas of the line, and the mixing ratio changes. This invention detects an error between a set mixture ratio and an actual measurement value, and controls the opening time of an electromagnetic on-off valve. That is, the set suction characteristic values shown in Fig. 3 are a, b, c, d, e (=0).
After measuring and calculating the error at multiple points using the solvent mixture ratio measurement mechanism, new parameters a', b', c', d', and e' are calculated. The parameters are then stored in the control unit and controlled by the parameters. Among the parameters, e' is a flow velocity correction value. By doing this, it is possible to obtain a liquid mixture with a more accurate solvent mixing ratio than when the electromagnetic switch is controlled based on the suction characteristics assumed from the time displacement of the plunger.

A UV detector or a flow meter placed in each flow path is used as a measurement mechanism for the solvent mixture ratio.

Next, an embodiment of the present invention will be explained with reference to FIG. In FIG. 1, numerals 1 and 2 are a storage chamber for solvent A and a storage chamber for solvent B, respectively, which are led to a solvent mixing chamber 5 via electromagnetic on-off valves 3 and 4. Reference numeral 6 indicates a reciprocating plunger pump, a UV detector 7 is connected to the downstream thereof, and a liquid feeding path to the measurement column system is configured. Reference numeral 8 indicates a control section of the electromagnetic on-off valve. The solid connecting lines between these indicate flow paths and the dotted connecting lines indicate electrical control connections.
The control unit 8 controls the opening time of the electromagnetic on-off valves 3 and 4 for each solvent based on set values. Fig. 3 shows an example of a suction curve of the suction process assumed from the change in position of the plunger of the plunger pump 6 over time.From the suction start time 0, there is a period a in which the plunger is displaced but the flow rate is delayed and the flow rate is not generated. Separate valve opening times are set for a period b during which the flow rate increases linearly, a period c during which the flow rate remains constant, and a period d during which the flow rate decreases. The dotted line at the center of this isosceles trapezoid indicates the point at which liquid A and liquid B are switched.

However, this set suction curve differs from the actual one as described above. FIG. 4 is an example of a suction curve calculated from the actual measurement values of the solvent mixture ratio measuring section.

Compared to the curves in Figure 3 above, the deviations are a′,
The time intervals are b', c', and d', and at the end of c', e indicates a value other than 0. This suction curve is, for example, a curve calculated from actual measured values from the mixture ratio measurement units at several points indicated on the curve. Therefore, if the opening times of the valves a, b, c, and d in FIG. This makes it possible to obtain a mixture of B liquid. Note that e, which was 0 in FIG. 3 but shows a value in FIG. 4, may be added separately as a correction coefficient to the control element.

FIG. 2 is a block diagram showing another embodiment. The difference from the one in FIG.
This shows the case where it is placed after 4. By actually measuring the flow rates of liquids A and B before entering the mixing chamber 3, the solvent mixing ratio can be determined, thereby obtaining the same actual measurement results as the actual measurement with the UV detector 5 described above. It is something that can be done.

As explained above, with this invention, it is possible to create a liquid mixture with a more accurate solvent mixing ratio than in the past, and this makes it possible to find optimal constant composition conditions using a liquid chromatograph that has a solvent mixing function. The results obtained have made it possible to replace liquid chromatographs without mixing functions with high reproducibility. In other words, high reproducibility can be obtained even if a solution with a constant composition is prepared in advance according to the settings of this device and analyzed using a device that does not have a mixing function.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a block diagram showing the configuration of another embodiment, and Fig. 3 is an example of a suction curve assumed from changes in the position of the plunger of a plunger pump over time. FIG. 4 is a diagram showing an example of a suction curve corrected by actual measurement by the solvent mixture ratio measuring section. 1, 2...Solvent storage chamber, 3, 4...Solenoid on-off valve, 5...Solvent mixing chamber, 6...Reciprocating plunger pump, 7...Solvent mixing ratio measuring section, 8...Solenoid on-off valve control section.

Claims (1)

[Claims] 1. 1 by mixing two or more types of solvents.
In a liquid chromatograph that uses two reciprocating plunger pumps to supply liquid as a developing agent,
An electromagnetic on-off valve is provided between each solvent storage chamber and a solvent mixing chamber, and a solvent mixing ratio measuring section is provided at the rear stage, and the measured value signal from this measuring mechanism is used to control the cam of the plunger pump. Calculates and stores a suction characteristic value obtained through actual measurement based on a suction characteristic value assumed from the time displacement of the plunger with suction characteristics measured based on the shape, etc., and controls the opening time of the electromagnetic opening/closing valve based on this suction characteristic value. A liquid chromatograph solvent mixing device equipped with a control unit.