JPH04110760A - Electroconductivity sensor with double temperature regulation - Google Patents

Abstract

PURPOSE:To provide practicability of decreasing change of the baseline with abrupt varying environmental temp. by furnishing two joints on the two sides of a replaceable preheat tube of double tube construction, supplying a measuring fluid to an electroconductivity sensor through the inner tubing, and exhausting it from the sheath tubing. CONSTITUTION:In a device to separate and analyze 14 the object component in a liquid to be measured chromatographically, the electroconductivity is sensed by a sensor 16. Therein the liquid introduced is passed through a joint 2 at the inlet and the inner tubing 1a of a preheat tube 1, and fed from a joint 3 at the outlet to a conductivity sensor 4. The liquid is sent in the reverse direction through the sheath tubing 1b of the preheat tube 1 and exhausted from the joint 2. Accordingly heat exchange is performed between the liquids flowing in the inner tubing 1a and sheath tubing 1b, and the temp. of the influx liquid to the sensor 4 and the temp. of the flowout liquid become the same substantially. Thus the temp. of the influx liquid to the sensor 4 is kept constant substantially, and the baseline of conductivity sensing signals will be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention is used as a detector in a device for chromatographically separating and analyzing a target component in a liquid to be measured, and detects the conductivity of a fluid. Regarding a conductivity detector with temperature control.

<Prior Art> As is well known, a liquid chromatograph is an apparatus that uses a liquid as a mobile phase to chromatographically separate and analyze target components in a liquid to be measured. In such a liquid chromatograph, a certain amount of the liquid to be measured is sampled and transported to a separation column with a solution of N as a mobile phase, and the separation column extracts the object to be measured (i.e., cations, etc.) in the liquid to be measured. Anions, etc.) are chromatographically separated, and then guided to a conductivity detector to detect conductivity, and the object to be measured in the liquid to be measured is measured from a talomadogram created based on the detection signal. It was like that.

However, in liquid chromatographs (including ion chromatographs), conductivity detectors are extremely temperature sensitive, and even though the conductivity of the fluid is the same, a 1°C change in temperature will result in a change in conductivity. Detector detection signal is approximately 2%
was also changing. Therefore, if the ambient temperature of the conductivity detector changes slightly or the temperature of the mobile phase changes due to pump pulsation, noise or fluctuations occur in the detection signal of the conductivity detector, resulting in highly sensitive detection of conductivity. It was starting to cause major problems.

In addition, in order to achieve high stability and high sensitivity, an attempt was made to minimize peak dispersion and obtain high stability by installing a heat exchange type preheating tube in front of the conductivity detector. Ta. This method has the great feature that high sensitivity and high stability can be easily obtained without providing a special temperature control mechanism in the detection section.

However, this method is not necessarily effective against rapid temperature changes in the environment in which the device is installed, and has the drawback of causing baseline drift and long-term undulation in environments with large temperature changes.

<Problem to be solved by the invention> The present invention was made in view of the above situation, and its purpose is to reduce fluctuations in the baseline even in response to sudden temperature changes in the external environment. An object of the present invention is to provide a conductivity detector with double temperature control.

Means for Solving the Problems> A feature of the present invention that solves the above-mentioned problems is that a double A conductivity detector with temperature control includes a heat exchange type preheating tube with a double tube structure, a first joint provided on the inlet side of the preheating tube, and a second joint provided on the outlet side of the preheating tube. , a conductivity detector for detecting the conductivity of the fluid, a heating box housing the heat exchange preheating tube, the first joint, the second joint, and the conductivity detector, and heating the heating box from both sides. first and second ends are provided, and the fluid supplied to the inner tube of the heat exchange type preheating tube through the first joint is supplied to the conductivity detector through the second joint. and the fluid discharged from the conductivity detector is configured to flow through the second joint into the outer tube of the heat exchange type preheating tube, and then to be discharged via the first joint. It is in.

<Example> Hereinafter, the present invention will be described in detail using the drawings. 1st
The figure is an explanatory view of the structure of the embodiment of the present invention, and FIG. 2 is a sectional view of the structure showing the stored state of the embodiment of the present invention. In Figures 1 and 2, 1 is a heat exchange type preheating tube with a double pipe structure;
a is the inner tube of the preheating tube, 1b is the outer tube of the preheating tube, 2 is the joint on the inlet side, 2a is the joint body, 2b to 2d are the first to third sockets for connecting the tube to the joint body 2a, 3 is a joint on the outlet side, 3a is a joint body, 3b to 3d are first to third sockets for connecting the tube to the joint body 3a, 4 is a conductivity detector, 4a is an electrode part, and 4b is an electrode part A resin cylinder covering 4a,
4c, 4c- are holders for fixing the electrode part 4a via the tube 4b; 4d, 4e are tubes la; oscines for connecting 5a to the conductivity detector 4; 6a, 6b are heaters; 7
A7b is a lead wire, 8 is an aluminum box, 9 is a heat insulating material, and 10 is an aluminum cover.

In the embodiment of the present invention having such a configuration, the first
The fluid introduced from the direction of the bold line arrow in the figure and FIG. It flows through the flow path from the inside of the inlet side joint 2 to the tube 5b, and is discharged in the direction of the thick arrow. Therefore, the liquid flowing in the inner tube 1a of the heat exchange type preheating tube 1 having a double tube structure (i.e., the liquid flowing into the conductivity detector 4) and the liquid flowing in the outer tube 1b (i.e., the liquid flowing into the conductivity detector 4). A heat exchange takes place between the temperature of the inflow liquid to the conductivity detector 4 and the temperature of the inflow liquid to the conductivity detector 4.
The temperature of the effluent from the two is approximately the same. Therefore, the temperature of the liquid flowing into the conductivity detector 4 is kept approximately constant, and as a result, the baseline of the conductivity detection signal is stabilized.

FIG. 3 shows an ion chromatograph (a type of liquid chromatograph) incorporating the embodiment of the present invention as described above,
FIG. 2 is an explanatory diagram of a usage example configuration of the present invention.

In this figure, = 11a is a tank in which an eluent consisting of, for example, 5mM HNO3 solution is stored, 12a is a pump that delivers the eluent, which is a mobile phase, at a constant flow rate, and 13 is a sample for collecting a fixed amount of sample (for example, 100 μm). 14 is a separation column filled with, for example, a cation exchange resin; 15 is a suppressor; 1
6 is a double tube type conductivity detector according to the present invention.

The conductivity detector 16 according to the present invention is housed in a heating box 17 and kept at a constant temperature (for example, 45'C).
is maintained. Also, sample injector 132 separation force ram 14 → suppressor, preheating tube 1. Conductivity detector 4. The heating box 17 is often housed in a constant temperature bath and kept at a constant temperature.

In the ion chromatograph having the configuration shown in FIG. 3, when the liquid feed pump 12a is driven, the eluent in the tank 11a flows from the liquid feed pump 12a to the sample injection at a flow rate of, for example, 2 ml/min. Vessel 13 - Separation force ram 1
4→The double tube type conductivity detector 16 according to the present invention is reached via the inner chamber of the suppressor 15, that is, the inner tube of the preheating tube 1→
conductivity detector 4 - the outer tube of the child heat tube 1), and finally flows to a waste liquid tank (not shown).

On the other hand, when the sample injector 13 is turned on, the liquid to be measured is injected into the eluent line, carried by the eluent, and reaches the separation column 14, where the ionic species in the liquid to be measured are chromatographed. Separated into Tsuku. The ionic species separated in this way are transported to the eluent again, pass through the inner chamber of the suppressor 15 - the inner tube of the preheating tube 1 → the conductivity detector 4 → the outer tube of the preheating tube 1, and finally Flows into a waste liquid tank (not shown).

Figures 4 to 7 are characteristic diagrams showing the degree of baseline improvement when using the embodiment of the present invention in comparison with the conventional example. In each figure, the horizontal axis represents the retention time T (unit: minutes). The vertical axis indicates the conductivity S (μS/C1rL). Furthermore, Fig. 4 shows the stability of the baseline over a long period of time (specifically, about 400 minutes) in an ion chromatograph incorporating the embodiment of the present invention, and Fig. 6 shows an ion chromatograph incorporating the conventional example. Long-term (specifically 40
(approximately 0 minutes) This shows the stability of the baseline. Furthermore, Fig. 5 shows the short-term (specifically, about 9 minutes) baseline stability of an ion chromatograph incorporating the embodiment of the present invention, and Fig. 7 shows the stability of the baseline of the conventional example. The baseline stability was observed using the built-in ion chromatograph over a short period of time (specifically, about 9 minutes).

As is clear from the characteristic diagrams of FIGS. 4 to 7, it can be seen that the baseline waviness is significantly smaller in the device incorporating the embodiment of the present invention. By the way, in Figure 6, 10n
The long-term undulation that was S/CIrL is 5 in Figure 4.
nS/Cm, and the waviness itself is smooth.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, if it is a liquid chromatography detector that is susceptible to temperature changes, it may be applied to a detector other than a conductivity detector. can also be applied.

<Effects of the Invention> According to the embodiments of the present invention as described in detail above, the second embodiment is used as a detector of an apparatus for chromatographically separating and analyzing a target component in a liquid to be measured, and detects the conductivity of a fluid. A conductivity detector with heavy temperature regulation includes a heat exchange type preheating tube with a double tube structure, a first joint provided on the inlet side of the preheating tube, and a second joint provided on the exit side of the preheating tube. , a conductivity detector, the heat exchange type preheating tube, and a first
A heating box that accommodates a joint, a second joint, and a conductivity detector, and first and second heaters that heat the heating box from both sides are provided, and the heat is supplied through the first joint. The fluid supplied to the inner pipe of the exchangeable preheating tube is supplied to the conductivity detector through the second joint, and the fluid discharged from the conductivity detector is passed through the second joint. It is configured to flow inside the jacket tube of the heat exchange type preheating tube and then be discharged via the first joint.

Therefore, a conductivity detector with dual temperature control is realized that can reduce baseline fluctuations caused by external temperature fluctuations and can perform stable and highly sensitive measurements over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional diagram of the configuration showing the storage state of the embodiment of the present invention, FIG. 3 is an explanatory diagram of the configuration of an example of use of the present invention, and FIGS. 4 to 7 is a characteristic diagram showing the degree of improvement of the baseline when using the embodiment of the present invention in comparison with the conventional example. 1... Preheating tube, 1a... Inner tube, 1b.
...--Outer tube, 23... Joint, 4... Conductivity detector, 4a... Electrode part, 4b... Tube, 4c, 4c-...Holder 4d, 4e...Osine, 6a, 6b...
... Heater, 7a, 7b ... Lead wire, 8.
...Box, 9...Insulation material, 10...
...Hippo 11a, 1 l b------tank, 2a, 12b...Liquid pump 3...Sample injector, 14...Separation Column 5...Suppressor, 6...Double tube conductivity detector 7 according to the present invention
・・・・・・Heating box

Claims (1)

[Claims] A conductivity detector with dual temperature control used as a detector for a device that chromatographically separates and analyzes target components in a liquid to be measured includes a heat exchange type preheating tube with a double tube structure,
a first joint provided on the inlet side of the preheating tube, a second joint provided on the outlet side of the preheating tube, a conductivity detector that detects the conductivity of the fluid, and the heat exchange type preheating tube, a heating box that accommodates a first joint, a second joint, and a conductivity detector, and first and second heaters that heat the heating box from both sides, Fluid supplied to the inner tube of the heat exchange type preheating tube is supplied to the conductivity detector through the second joint, and fluid discharged from the conductivity detector is supplied through the second joint. A conductivity detector with dual temperature regulation configured to flow inside the jacket tube of the heat exchange type preheating tube and then be discharged through the first joint.