JP2008215978A - Liquid feed pump and liquid chromatograph using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid feed pump capable of keeping a mass flow rate constant, and a liquid chromatograph using it. <P>SOLUTION: The liquid feed pump 40 is equipped with a pump head 20 having a pump chamber 21 with which an inflow passage for permitting only the inflow of a mobile phase and an outflow passage for permitting only the outflow of the mobile phase communicate and a mechanism 4 for sucking and discharging the mobile phase by reciprocally moving a piston 13 in the pump chamber 21 and further equipped with a memory part 42 for storing a model formula related to the volume expansion coefficient of the mobile phase and the volumetric change of the mobile phase due to temperature and a motor control part 52 outputting a control signal, which controls the moving speed or distance of the piston 13, to the mechanism 4 in order to increase and decrease the feed liquid amount of the mobile phase on the basis of the temperature related to the mobile phase measured by a temperature measuring part 30, the volume expansion coefficient and the model formula. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid feed pump and a liquid chromatograph, for example, a GPC (gel permeation chromatograph) liquid feed pump used for measurement of molecular weight distribution and a liquid chromatograph using the same.

As shown in FIG. 3, the liquid chromatograph includes a reservoir 2 in which a mobile phase is stored, a first pipe 9 a that communicates the reservoir 2 and the degasser 3, a degasser 3 that degass the mobile phase, and a degasser 3. A first pipe 9b that communicates with the liquid feed pump body 4, a liquid feed pump body 4, a second pipe 9c that communicates between the liquid feed pump body 4 and the sample injector 5, and a sample injector into which a sample is introduced 5, a column 6 and a detector 7 are provided in this order along the flow path of the mobile phase.
In such a liquid chromatograph, a reciprocating piston type mechanism (liquid feed pump body) 4 is generally used as a mechanism (liquid feed pump body) 4 for feeding a mobile phase.

FIG. 2A and FIG. 2B are diagrams showing the configuration of a reciprocating piston type mechanism (liquid feed pump main body) 4. The mechanism (liquid feed pump main body) 4 includes a piston drive unit 10 and a pump head 20.
In the piston drive unit 10, the cross head 12 slidably inserted into the body case 11 has a piston 13 at one end and a rotatable disk-shaped bearing 14 at the other end. Yes. Between the end face of the cross head 12 on which the piston 13 is fixed and the end face inside the main body case 11, a spring 15 is disposed so as to separate the end faces. On the other hand, the peripheral edge of the bearing 14 of the cross head 12 is in contact with the peripheral edge of a substantially elliptical plate-shaped cam 16 that is rotated by a motor (not shown).
Thus, when the cam 16 is rotated by driving the motor, the rotational motion is determined by the cam profile of the cam 16 via the bearing 14 pressed against the periphery of the cam 16 by the force of the spring 15. Is converted into a reciprocating motion. That is, the reciprocating motion of the piston 13 in the horizontal direction is created.

  A pump chamber 21 is formed inside the pump head 20. A first check valve 23 is disposed in the inflow path 22 provided on the lower surface of the pump chamber 21, and a second check valve is provided in the outflow path 24 provided on the upper surface of the pump chamber 21. 25 is arranged. Further, the pump chamber 21 is formed with a piston seal attachment port 26 to which a piston seal 27 is attached. The piston seal 27 has a passage on the central axis, and the piston 13 is inserted into the pump chamber 21 through this passage.

  Therefore, the piston 13 is pushed most into the pump chamber 21 as shown in FIG. 2A and the position (discharge start point) most pulled out into the pump chamber 21 as shown in FIG. The mobile phase is sucked into the pump chamber 21 from the inflow path 22 through the first check valve 23 by reciprocating between the position (suction start point) and the mobile phase sucked into the pump chamber 21. Is discharged out of the pump chamber 21 from the outflow passage 24 through the second check valve 25. At this time, the piston 13 moves at a constant moving speed, whereby the mobile phase is discharged at a constant flow rate.

However, for example, when acetone is used as the mobile phase used in the liquid chromatograph, the volume expansion coefficient per 1 ° C. is 0.143%, and the mass flow rate of the liquid feed pump is constant. The flow rate depends greatly on the temperature. Generally, the following formula (1) is established in the relationship between the volume V of the liquid (mobile phase) and the temperature t.
V = V ₀ (1 + βt) (1)
Here, V ₀ is the volume of the liquid at 0 ° C., and β is a volume expansion coefficient specific to the liquid.
Table 1 shows an example of the liquid used as the mobile phase and its volume expansion coefficient β.

Therefore, in the conventional GPC used for measuring the molecular weight distribution, even if the volume flow rate is always 1.000 ml / min with a liquid feed pump using a mobile phase having a volume expansion coefficient β of 1 × 10 ⁻³ , When the temperature increased by 1 ° C., the mass flow rate changed, and as a result, the elution time (elution time) of the obtained sample component varied from, for example, 10.00 min to 10.01 min.
Therefore, in GPC, in order to obtain good reproducibility of the elution time, the mobile phase and the pump head are kept at a constant temperature (see, for example, Patent Document 1). Specifically, the temperature of the heat balance coil 61 for passing the mobile phase and the aluminum block 62 connected to the pump head as shown in FIG. Is provided with a circulation thermostat 63 for keeping the temperature constant. Accordingly, the mass flow rate from the mechanism (liquid feed pump main body) is always kept constant by keeping the mobile phase and the pump head at a constant temperature.
Japanese Patent No. 2516332

However, in order to keep the mobile phase and the pump head at a constant temperature, a heat retention control mechanism is required, and the liquid chromatograph apparatus itself becomes complicated and the cost is increased.
Then, an object of this invention is to provide the liquid feeding pump which can keep a mass flow rate constant, and a liquid chromatograph using the same.

  The liquid delivery pump of the present invention, which has been made to solve the above-described problems, has a pump head having a pump chamber in which an inflow passage that allows only inflow of a mobile phase and an outflow passage that allows only outflow of the mobile phase as a pump head. A liquid feed pump having a mechanism for sucking and discharging the mobile phase by reciprocating a piston in the pump chamber, and further, volumetric expansion coefficient of the mobile phase or volume change of the mobile phase due to temperature Based on the temperature related to the mobile phase measured by the temperature measurement unit, the volume expansion coefficient, or the model formula, the mechanism is controlled to A motor control unit that outputs a control signal for controlling the moving speed or moving distance of the piston.

According to the liquid feed pump of the present invention, for example, the temperature measurement unit constantly measures the temperature change of the mobile phase in the reservoir. When the mechanism (liquid pump main body) is activated, the piston reciprocates, thereby moving the mobile phase from the reservoir to the sample injector.
At this time, for example, when a mobile phase having a volume expansion coefficient β of 1 × 10 ⁻³ is used, when the temperature measurement unit senses that the temperature of the mobile phase has increased by 1 ° C., the motor control unit If the volume flow rate V _ts of the mobile phase at the start of measurement is 1.000 ml / min, the current volume flow rate V _tg of the mobile phase is 1. The piston moving speed was increased so as to be 001 ml / min (= 1.000 [ml / min] × (1 + 1 × 10 ⁻³ × 1 [° C.]), and conversely, the temperature decreased by 1 ° C. When the temperature measurement unit senses, the motor control unit determines that the volume flow rate V _tg is 0.999 ml / min (= 1.000 [ml / min] based on the volume expansion coefficient β of the mobile phase according to the following equation (2). ] × (1 + 1 × 10 ⁻³ × (−1) [° C.])) Then, a control signal for slowing the moving speed of the piston is output to the mechanism (liquid feed pump main body).
V _tg = V _ts + V _ts × β × (tg−ts) (2)
Here, ts is the temperature of the liquid (mobile phase) at the start of measurement, and tg is the current temperature of the liquid.

  Therefore, according to the liquid feed pump of the present invention, for example, by outputting a control signal for controlling the moving speed of the piston to the mechanism (liquid feed pump body) based on the temperature and the volume expansion coefficient or the model formula. The mass flow rate of the mobile phase can be kept constant. Therefore, the elution time of the sample component can be prevented from fluctuating due to a change in temperature related to the mobile phase without complicating the apparatus itself.

(Means and effects for solving other problems)
Further, the liquid chromatograph of the present invention includes a reservoir for storing the mobile phase, a first pipe, a liquid feed pump, a second pipe, a sample injector for introducing a sample, a column, and a detector through the flow path of the mobile phase. The first pipe communicates with the reservoir and the inflow path, and the second pipe communicates with the outflow path and the sample injector. The liquid feed pump includes a pump chamber having a pump chamber communicating with an inflow passage allowing only the mobile phase inflow and an outflow passage allowing only the mobile phase outflow, and reciprocates the piston in the pump chamber. Thus, the mechanism for sucking and discharging the mobile phase, the storage unit for storing the model expression relating to the volume expansion coefficient of the mobile phase or the volume change of the mobile phase due to temperature, and the mobile phase measured by the temperature measuring unit A motor control unit that outputs a control signal for controlling the moving speed or moving distance of the piston to the mechanism in order to increase or decrease the liquid feeding amount of the mobile phase based on the temperature and the volume expansion coefficient or the model equation; I have to prepare.
In the liquid chromatograph of the present invention, the temperature measuring unit includes a group of a room temperature, a mobile phase in the reservoir, a mobile phase in the first pipe, a mobile phase in the second pipe, and a mobile phase in the pump head. At least one temperature selected from the above may be constantly measured.
Furthermore, the liquid chromatograph of the present invention may further include a degasser for degassing the mobile phase, and the temperature measuring unit may measure the temperature of the mobile phase in the degasser.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and it goes without saying that various aspects are included without departing from the spirit of the present invention.

FIG. 1 is a diagram showing a schematic configuration of a liquid chromatograph according to the present invention.
The liquid chromatograph includes a reservoir 2 in which a mobile phase is stored, a first pipe 9a, a degasser 3 for degassing the mobile phase, a first pipe 9b, and a liquid feed pump 40 according to an embodiment of the present invention. The second pipe 9c, the sample injector 5 into which the sample is introduced, the column 6, and the detector 7 are provided in this order along the flow path of the mobile phase. Furthermore, the liquid chromatograph includes a temperature measurement unit 30 that measures the temperature of the mobile phase.

The reservoir 2 stores a mobile phase.
The degasser 3 degass the mobile phase.
The first pipe 9 a communicates the reservoir 2 and the degasser 3. The first pipe 9 b communicates the degasser 3 and the mechanism (liquid feed pump main body) 4. Further, the second pipe 9 c communicates the mechanism (liquid feed pump body) 4 and the sample injector 5.
The first pipe and the second pipe are, for example, polytetrafluoroethylene tubes.

The column 6 is maintained at a constant temperature by the column oven 8. Then, the sample introduced from the sample injector 5 is separated in the time axis direction while passing through the column 6 and reaches the outlet end of the column 6.
The detector 7 is connected to the outlet end of the column 6 and detects the reached sample component.

  The temperature measuring unit 30 constantly measures the temperature change of the mobile phase in the reservoir 2 and, for example, a heat sensitive body such as a platinum resistor or a thermistor is immersed in the mobile phase. Further, the temperature detection signal of the temperature measurement unit 30 is output to a temperature data acquisition unit 54 described later.

The mechanism (liquid feed pump main body) 4 includes a piston drive unit 10 and a pump head 20. In addition, about the same structure as the mechanism (liquid feeding pump main body) 4 shown to Fig.2 (a) and FIG.2 (b), while using the same code | symbol, description is abbreviate | omitted.
In the liquid feed pump 40 according to the embodiment of the present invention, the rotational speed of the motor that rotates the cam 16 is increased so that the moving speed of the piston 13 can be increased or the moving speed of the piston 13 can be decreased. The control is executed when a control signal output from a motor control unit 52 described later is given. Note that a user set value is used as the initial set value (the V _ts ).

Such a liquid feed pump 40 has a calculation unit 41, and further has a volume expansion coefficient storage unit (storage unit) 42 for storing the volume expansion coefficient β of the mobile phase, and a keyboard (not shown) as an input device. Are connected.
The volume expansion coefficient storage unit 42 stores the volume expansion coefficient β of the mobile phase. For example, the volume expansion coefficient β of the mobile phase used for the measurement is previously determined by the user before starting the measurement with the input device. It will be memorized.
The temperature data acquisition unit 54 acquires a temperature detection signal from the temperature measurement unit 30.

Based on the acquired temperature (temperature detection signal) and the volume expansion coefficient β stored in the volume expansion coefficient storage unit 42, the motor control unit 52 determines the rotation speed of the motor of the mechanism (liquid pump main body) 4. A control signal to be controlled is output.
For example, when a mobile phase having a volume expansion coefficient β of 1 × 10 ⁻³ is used, when a temperature detection signal in which the temperature of the mobile phase is increased by 1 ° C. is input, based on the volume expansion coefficient β of the mobile phase, According to the above equation (2), when the volume flow rate V _ts of the mobile phase at the start of measurement is 1.000 ml / min, the volume flow rate V _tg corrected according to the current temperature is 1.001 ml / min. When the temperature detection signal with the temperature decreased by 1 ° C. is input to the motor, the volume flow rate V _ts is set to 0.999 ml / min according to the above equation (2). Try to slow down the rotation speed. As a result, the mobile phase is discharged at a constant mass flow rate.

  As described above, according to the liquid feed pump 40, the control signal for controlling the moving speed of the piston 13 to the mechanism (liquid feed pump body) 4 based on the temperature of the mobile phase in the reservoir 2 and the volume expansion coefficient β. Is output, the mass flow rate of the mobile phase can be kept constant. Therefore, it is possible to prevent the elution time of the sample component from fluctuating due to a change in temperature without complicating the apparatus itself.

(Other embodiments)
(1) In the liquid chromatograph described above, the motor control unit 52 is configured to output a control signal for controlling the rotation speed of the motor of the mechanism (liquid pump main body) 4. A configuration may be adopted in which a control signal for increasing or decreasing the piston movement distance (crosshead movement distance) L is output (see FIG. 5). Specifically, in the mechanism (liquid feed pump main body) such as the ball screw system instead of the cam system described above, the position (discharge start point) most pulled out into the pump chamber as shown in FIG. As shown in FIG. 5A, the position most pushed into the pump chamber (suction start point) is varied. Further, the suction start point may be fixed and the discharge start point may be varied.
(2) In the liquid chromatograph described above, the temperature measuring unit 30 is configured to measure the temperature of the mobile phase in the reservoir 2, but the room temperature, the mobile phase in the first pipes 9a and 9b, the pump head 21, and the like. It is good also as a structure which measures the temperature of the mobile phase in the inside, the mobile phase in the degasser 3, and the mobile phase in the 2nd piping 9c, and it is good also as a structure by which a temperature measurement part is provided in several places (FIG. 1 and FIG. (See FIG. 2).
(3) In the liquid chromatograph described above, the motor controller 52 is configured to output a control signal for controlling the rotational speed of the motor of the mechanism (liquid feed pump body) 4 based on the above equation (2). The control signal for controlling the rotational speed of the motor of the mechanism (liquid feed pump main body) may be output based on the above equation (1).

(4) In the liquid chromatograph described above, the temperature measurement unit 30 is immersed in the mobile phase. However, the temperature measurement unit 30 is directly attached to the first pipe or the second pipe, or attached to the outside of the pump head block. It is good also as a structure which does not contact liquid.
(5) In the liquid chromatograph described above, the motor control unit 52 is configured to output a control signal for controlling the rotational speed of the motor of the mechanism (liquid feed pump body) 4 based on the above equation (2). The control signal for controlling the rotational speed of the motor of the mechanism (liquid pump main body) may be output based on the following higher-order polynomial (3). Also, when the density change of water etc. changes complicatedly with temperature, it is corrected according to the liquid-specific model formula (model formula related to the volume change of the mobile phase due to temperature), and the mechanism (liquid pump main body) It is good also as a structure which outputs the control signal which controls the rotational speed of this motor.
V = V ₀ (1 + β ₁ t + β ₂ t ² + β ₃ t ³ ) (3)
Here, V ₀ is the volume of the liquid (mobile phase) at 0 ° C., and β _1, β _{2, and} β ₃ are volume expansion coefficients specific to the liquid.

  The liquid feed pump and the liquid chromatograph using the same according to the present invention are used for, for example, GPC used for measurement of molecular weight distribution.

It is a figure which shows schematic structure of the liquid chromatograph concerning this invention. It is a figure which shows the structure of a reciprocating piston type mechanism (liquid feeding pump main body). It is a figure which shows schematic structure of a liquid chromatograph. It is a figure which shows schematic structure of the heat retention control mechanism used for a liquid chromatograph. It is a figure which shows the structure of another example of a reciprocating piston type mechanism (liquid feeding pump main body).

Explanation of symbols

2 Reservoir 3 Degasser 4 Mechanism (Liquid feed pump body)
DESCRIPTION OF SYMBOLS 5 Sample injector 6 Column 7 Detector 9a, b 1st piping 9c 2nd piping 13 Piston 20 Pump head 21 Pump chamber 30 Temperature measurement part 40 Liquid feeding pump 41 Calculation part 42 Volume expansion coefficient memory | storage part (memory | storage part)
52 Motor control unit 54 Temperature data acquisition unit

Claims (4)

The pump head is provided with a pump chamber in which an inflow passage allowing only the mobile phase inflow and an outflow passage allowing only the mobile phase outflow, and the piston is reciprocated in the pump chamber. A liquid feed pump having a mechanism for sucking and discharging
Further, a storage unit for storing a model expression relating to a volume expansion coefficient of the mobile phase or a volume change of the mobile phase due to temperature,
Based on the temperature related to the mobile phase measured by the temperature measuring unit and the volume expansion coefficient or model equation, the moving speed or moving distance of the piston is controlled by the mechanism in order to adjust the liquid feeding amount of the mobile phase. A liquid feed pump comprising: a motor control unit that outputs a control signal. A reservoir in which the mobile phase is stored;
First piping,
Feed pump,
Second piping,
A sample injector into which the sample is introduced,
column,
A liquid chromatograph comprising detectors in this order along the flow path of the mobile phase,
The first pipe communicates the reservoir and the inflow path, and
The second pipe communicates the outflow path and the sample injector,
The liquid feeding pump includes a pump chamber in a pump head that communicates an inflow path that allows only the mobile phase to flow in and an outflow path that allows only the mobile phase to flow out, and reciprocates the piston in the pump chamber. A mechanism for sucking and discharging the mobile phase,
A storage unit for storing a model expression relating to a volume expansion coefficient of the mobile phase or a volume change of the mobile phase due to temperature;
Based on the temperature related to the mobile phase measured by the temperature measuring unit and the volume expansion coefficient or model equation, the moving speed or moving distance of the piston is controlled by the mechanism in order to adjust the liquid feeding amount of the mobile phase. A liquid chromatograph comprising a motor control unit that outputs a control signal.   The temperature measurement unit always has at least one temperature selected from the group consisting of room temperature, a mobile phase in a reservoir, a mobile phase in a first pipe, a mobile phase in a second pipe, and a mobile phase in a pump head. The liquid chromatograph according to claim 2, which is measured. Furthermore, a degasser for degassing the mobile phase is provided,
The liquid chromatograph according to claim 2, wherein the temperature measuring unit measures a temperature of a mobile phase in the degasser.

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