JPH0456152B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a liquid chromatograph, and particularly to a liquid chromatograph that uses a reciprocating plunger pump as a liquid feeding pump, and that the pump is equipped with a pressure sensor for monitoring liquid feeding pressure. Related to liquid chromatographs.

(B) Prior Art One of the important conditions in high-performance liquid chromatography analysis is stable liquid feeding, and the pressure of the liquid feeding pump is one guideline for the stability of liquid feeding. Conventional high-performance liquid chromatographs often use pressure gauges or upper (and lower) pressure limiters (which can automatically stop liquid feeding when the pressure exceeds a set value). However, although this method can detect blockages and leaks in the flow path, it is also possible to detect increases in pulsation due to the inclusion of air bubbles and drift in pressure values, which can have a major impact on analysis. Cannot be detected immediately. In particular, automatic operation of analytical equipment,
Today, when unmanned driving is becoming a social demand, the inability to detect such conditions could be a fatal flaw.

(c) Purpose of the Invention This invention was made in view of the above circumstances, and one of its main objectives is to prevent not only clogging and leakage in the flow path, but also pulsation caused by air bubbles, etc. The purpose of the present invention is to provide a liquid chromatograph that can instantly self-diagnose pressure increases and drifts in pressure values.

(D) Structure of the Invention The present invention provides a liquid chromatograph in which a reciprocating plunger pump is used as a liquid pump and the pump is equipped with a pressure sensor. A pressure change rate detecting means for detecting a change, a pressure change rate integrating means for integrating a pressure change rate detected by this means, and a pressure change rate obtained by these means and its integral value are each set. A liquid chromatograph equipped with a state determination means for determining the state of a pump by comparing the value with the value, and a control means for issuing a control signal such as interrupting analysis or warning when at least one of the rate of pressure change and its integral value is abnormal. It is a graph.

(e) Examples This invention will be described in detail below based on examples shown in the figures. Note that this invention is not limited by this.

First, in FIG. 1, a high-performance liquid chromatograph 1 basically includes a carrier liquid tank 2, a reciprocating plunger pump 3, a sample introduction device 4, an analytical column 5 in a column oven 8, a detector 6, and a data processing device 7. In preparation for this, a pressure sensor 9 is further installed on the discharge side of the plunger pump 3. 10 to 15 are interfaces; the interface 10 sends a flow rate setting value, that is, an on/off signal, from the microprocessor 16 to the plunger pump 3; the interface 11 sends a sample value of pressure at a certain point in time from the pressure sensor 9; (signal) can be read into the microprocessor 16. Further, the interfaces 12 to 15 can send control signals from the microprocessor 16 to each of the devices 4 to 7 according to analysis conditions. Note that 17 is a memory, A is the hardware of the microcomputer, and B is the hardware of its application equipment.

Next, the microprocessor 16 and memory 17
To explain in detail the relationship between this and the basic configuration of the device 1, in FIG.
19 is a pressure change rate integrating means that integrates the pressure change rate; 20 is a pressure change rate and its integral value obtained by both of these means, which are set in advance; The control means includes a state determining means for determining the state of the plunger pump by comparing the set values with the set values determined, and a control means for issuing a control signal to each device 4, 8, . . . , 7 based on the result of the state determination. 21 is a plunger pump driving means;
22 is the flow rate setting means.

Here, the operation of each of the above-mentioned means will be explained, and the structure of each means will be clarified in more detail.

First, the pressure change rate detection means 18 samples the pressure signal from the pressure sensor 9 at predetermined time intervals (sampling period T _S ), and determines the upper and lower limits of pulsation from the sampled values, although it can be specifically configured with an electronic circuit. Calculate the pressure fluctuation range close to . The specific sampling period T _S is desirably set to be slightly larger or slightly smaller than 1/2 of the period T of one stroke of the pump so as not to be synchronized with the suction-discharge stroke of the pump. For example, if the discharge amount V in one discharge stroke of the plunger is 0.1ml, and the set flow rate F is 0.5ml/min,
T=60V/F=12 seconds. On the other hand, if T _S is set to 4 seconds, a value close to the upper and lower pressure limits will be obtained at some point during several measurements. Of course, a method may also be adopted in which the pressure waveform is differentiated at high speed and the true upper and lower limit pressures are read.

By reading the pressure at the timing determined in this way and examining the rate of change in the pressure, especially the fluctuation range, it is possible to detect not only when the upper and lower limits are exceeded, but also the rapid changes leading up to them.

Next, the rate of pressure change thus detected is integrated by the integrating means 19. Specifically, this means can be constituted by an integrating circuit. After all, by integrating the rate of pressure change, it is possible to detect pressure drifts and waviness due to changes in the state of the column over a relatively long period of time, which cannot be detected using only the rate of pressure change.

As described above, the pressure change rate and its integral value detected by both means are compared with each set value by the state determination means and control means 20 consisting of a microcomputer, and if stable, the series of analyzes is continued. Alternatively, a signal to start the analysis can be sent, and if unstable (abnormal), a signal to stop, interrupt, or alarm the analysis can be sent to each device.

A flowchart of the software that implements these functions is shown in FIG. Here, △p is the pressure change rate, p ₁ is the current pressure sample value, p ₀ is the previous pressure sample value, s is the integral value of the pressure change rate,
N is the number of samplings. Further, a, n, and b are set values for the rate of pressure change, the number of sampling times, and the integral value, respectively, which are determined from the characteristics of the liquid pump and are either fixed or set to be changed depending on the operating conditions.

Note that, although the state determining means and the control means 20 are constituted by one microcomputer, they may be constituted by two computers corresponding to both means.

(f) Effects of the Invention This invention is configured to detect the rate of change in the pressure fluctuation range of the pump and the integral value of the rate of change, and control each device accordingly. It is possible to detect increases in pressure values, drifts or undulations in pressure values, and to prevent analysis under such unstable liquid feeding conditions, ensuring highly accurate and reliable analysis. Of course, this invention is suitable for automatic and unmanned operation of liquid chromatographs.

[Brief explanation of the drawing]

FIG. 1 is a functional explanatory diagram showing one embodiment of the liquid chromatograph of the present invention, FIG. 2 is a functional explanatory diagram of its main parts, and FIG. 3 is a flowchart thereof. DESCRIPTION OF SYMBOLS 1... High-speed liquid chromatograph, 3... Plunger pump, 9... Pressure sensor, 18... Pressure change rate detection means, 19... Pressure change rate integration means, 2
0...Status determination means and control means.

Claims (1)

[Claims] 1. In a liquid chromatograph in which a reciprocating plunger pump is used as a liquid pump and the pump is equipped with a pressure sensor, a change in the pressure fluctuation width of the pump is detected based on a pressure signal from the pressure sensor. A pressure change rate detecting means for detecting a pressure change rate, a pressure change rate integrating means for integrating a pressure change rate detected by this means, and comparing the pressure change rate obtained by these means and its integral value with each set value. A liquid chromatograph comprising: a state determination means for determining the state of a pump; and a control means for issuing a control signal such as an interruption of analysis or an alarm when at least one of the rate of pressure change and its integral value is abnormal. 2. The liquid chromatograph according to claim 1, wherein the change in pressure fluctuation width is detected at a time interval shorter than one reciprocating time of the plunger.