JP2011013044A - Electric conductivity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric conductivity detector which has a good output linearity for an ion concentration contained in liquid eluted from a separation column and whose measuring cell capacity is small.SOLUTION: The electric conductivity detector includes two working electrodes arranged in parallel, two measuring electrodes arranged so as to be parallel to and sandwiched by the two working electrodes, an insulator for filling a space between the two working electrodes, a channel which is arranged so as to contact with the two working electrodes and the two measuring electrodes and brings the liquid to flow therein, and a measuring cell which brings current flowing into/out of the measuring electrodes to be extremely small, thereby solving the problem.

Description

  The present invention relates to an electrical conductivity detector, and more particularly to an electrical conductivity detector used in liquid chromatography.

  Among liquid chromatography, ion chromatography is a method mainly used for separation and quantification of inorganic cations, inorganic anions, organic acids or amines. The amount of ions eluted by the conductivity detector is measured.

  Although the analysis time of ion chromatography has been shortened by improving the performance of column separation agents and increasing the pressure resistance of the entire system, the conductivity detector used to detect the eluted ions has low output linearity. Therefore, it is necessary to measure with many samples of known concentration to create a calibration curve. Therefore, the merit of shortening the analysis time by the separating agent and system cannot be fully utilized. Therefore, in order to further shorten the analysis time of ion chromatography, an electrical conductivity detector having good output linearity with respect to the eluted ion concentration and a small cell capacity is required.

  The electrical conductivity detector usually has a measuring cell (10) having a structure in which a liquid eluted from a separation column flows between two electrodes (11) installed in parallel, and a voltage is applied between the two electrodes. The current value at the time of applying is measured as the electric conductivity (FIG. 1). At this time, when a DC voltage is applied between the electrodes, polarization occurs around the electrodes and the electric conductivity of the solution cannot be detected correctly. Therefore, measurement is usually performed by an AC impedance method in which an AC voltage of about 1 kHz is applied. Since the impedance of the liquid eluted from the separation column is related to the ion concentration in the eluate, the alternating current impedance method measures the ion concentration using the above relationship.

  In an electric conductivity detector (Fig. 1) having a measurement cell consisting of two commonly used electrodes, the measured impedance depends on the electrode / electrolyte interface impedance in addition to the impedance due to the electric conductivity of the mobile phase. . Since the ratio of the interfacial impedance increases as the ion concentration increases, the measurement responsiveness decreases, causing a decrease in the linearity of the calibration curve.

  As a method for reducing the influence of the electrode / electrolyte interface impedance, there is a method using a measurement cell (FIG. 2) comprising two working electrodes (12) and two measurement electrodes (13), and the measurement cell is used for liquid chromatography. By applying it to an electrical conductivity detector, the current flowing into and out of the measurement electrode is reduced, so that the influence of the interface impedance can be reduced (Patent Document 1). However, even when the measurement cell of Patent Document 1 is used, since the current flows in and out (70) to the measurement electrode (13) (FIG. 2), the path through which the current flows changes depending on the ion concentration.

  Moreover, when trying to reduce the measurement cell capacity of Patent Document 1 for the purpose of performing microanalysis and / or high sensitivity analysis, there are the following problems. When attempting to reduce the cell capacity by narrowing the inner diameter of the flow path, the working electrode (12), the measuring electrode (13), and the working electrode (12) -measuring electrode (13) or measuring electrode (13)- There is a problem that it becomes difficult to align the center of the flow path (15) through which the liquid eluted from the separation column passes through the insulator (14) between the measurement electrodes (13), and the peak expands inside the measurement cell. . Also, when trying to reduce the cell capacity by reducing the distance between the electrodes (12, 13), there is a problem of the influence of the electrode / electrolyte interface impedance due to the shortening of the length between the measurement electrodes (13). .

JP-A-57-189052

  An object of the present invention is to provide an electric conductivity detector for liquid chromatography having good output linearity with respect to ion concentration contained in a liquid eluted from a separation column and a small measuring cell capacity.

The present invention made in view of the above problems includes the following inventions:
The first invention is
Two working electrodes installed in parallel,
Two measuring electrodes placed parallel to and between the two working electrodes, and
An insulator filling between the two working electrodes;
A flow path for flowing a liquid, placed in contact with the two working electrodes and the two measuring electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
It is an electrical conductivity detector for liquid chromatography, characterized in that current flows into and out of the measurement electrode very little.

The second invention is
Two working electrodes installed in parallel,
Two measuring electrodes placed parallel to and between the two working electrodes, and
An insulator filling between the two working electrodes;
A flow path for flowing a liquid, placed in contact with the two working electrodes and the two measuring electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
The length of the contact region between the measurement electrode and the flow channel in the measurement cell is sufficiently shorter than the distance between the two measurement electrodes and / or the inner diameter of the flow channel, for liquid chromatography It is an electrical conductivity detector.

The third invention is
Two working electrodes installed in parallel,
Two flat measurement electrodes installed in a position parallel to and sandwiched between the two working electrodes;
Two insulators filling the gap between the working electrode and the measuring electrode;
An insulator filling between the two plate measuring electrodes;
A flow path for flowing liquid, penetrating the two working electrodes, the two plate measuring electrodes, and the three insulators;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
In the measurement cell, the length of the contact area between the flat plate measurement electrode and the flow path is the length of the contact area between the insulator and the flow path that fills the space between the two flat plate measurement electrodes and / or the flow path. An electric conductivity detector for liquid chromatography characterized by being sufficiently shorter than the inner diameter.

  According to a fourth aspect of the present invention, the length of the contact area between the flat plate measurement electrode and the flow path is the length of the contact area between the insulator and the flow path that fills between the two flat plate measurement electrodes and / or the flow path. The electrical conductivity detector according to the third aspect of the present invention, wherein the electrical conductivity detector is 1/5 or less of the inner diameter of the first invention.

The fifth invention is
Two working electrodes installed in parallel,
Two rod-shaped or needle-shaped measuring electrodes installed at a position parallel to and sandwiched between the two working electrodes,
An insulator filling between the two working electrodes;
A flow path for flowing liquid, penetrating the two working electrodes and the insulator, and being in contact with one end of the two measuring electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
In the measurement cell, the electrical conductivity detector for liquid chromatography is characterized in that an outer diameter of the measurement electrode is sufficiently shorter than an interval between the measurement electrodes and / or an inner diameter of the flow path.

  A sixth aspect of the present invention is the electrical conductivity detector according to the second to fifth aspects of the present invention, further comprising a measuring cell on one side or a pair of electrodes on both sides outside the two working electrodes. It is.

  According to a seventh aspect of the present invention, there is provided an electrical conduction apparatus according to any one of the second to sixth aspects, further comprising a measurement cell further provided with one or two electrodes on the outer surface of the insulator located between the two measurement electrodes. It is a degree detector.

  Hereinafter, the present invention will be described in detail.

  The shape of the working electrode in the measurement cell for an electrical conductivity detector of the present invention is not particularly limited as long as the flow path through which the liquid flows, and as an example, from a block shape including a joint for connecting to other piping. The working electrode can be raised. Also, the shape of the measurement electrode is not particularly limited, but in general, a flat plate electrode having a constant thickness and a through hole, a rod-like electrode having a constant outer diameter, a needle-like electrode having a needle-like end, etc. Used.

  The working electrode and measurement electrode in the measurement cell for electrical conductivity detector of the present invention may be made of any material that has conductivity and resistance to the mobile phase used in liquid chromatography, such as stainless steel, gold And platinum. In addition, the material of the insulator in the measurement cell for electrical conductivity detector of the present invention may be any material that has insulating properties and resistance to the mobile phase used in liquid chromatography, and is generally polytetrafluoroethylene. (PTFE) or the like is used.

  Next, the length of the contact area between the two measurement electrodes and the flow path in the present invention will be described. When a flat plate electrode is used as the measurement electrode, it means the length of the part where the flow path passes through the measurement electrode with respect to the direction in which the liquid flows, and when the plane of the electrode and the direction in which the liquid flows are orthogonal to each other The thickness of the electrode becomes the length of the contact area as it is. When a rod-like or needle-like electrode is used as a measurement electrode, it refers to the length with respect to the direction in which the liquid flows in the portion where the electrode and the flow path are in contact, and the axis of the electrode and the direction in which the liquid flows When orthogonal, the outer diameter of the portion in contact with the electrode becomes the length of the contact area as it is.

  The length of the contact region is preferably as short as possible. In particular, when the distance between the two measurement electrodes and / or the inner diameter of the flow path is sufficiently short, the distance between the measurement electrodes is smaller than that of the conventional measurement cell disclosed in Patent Document 1. Current in / out can be reduced. In particular, when a flat plate electrode is used as the measurement electrode, the length of the contact region is set to the length of the contact region between the insulator and the channel filling the gap between the electrodes and / or the inner diameter of the channel passing through the electrode. On the other hand, when it is 1/5 or less, when a rod-like or needle-like electrode is used as the measurement electrode, the outer diameter of the electrodes is relative to the distance between the electrodes and / or the inner diameter of the flow path in contact with the electrodes. When it is 1/5 or less, it is preferable because the current flowing between the measurement electrodes can be further reduced.

  Another aspect of the measurement cell for an electrical conductivity detector according to the present invention is a measurement cell in which two measurement electrodes of the measurement cell are arranged at positions recessed with respect to the direction of liquid flow. it can. As an example of the measurement cell, when the measurement electrode is a flat plate electrode, the measurement is made such that the inner diameter of the flow path penetrating the flat plate measurement electrode is larger than the inner diameter of the flow path penetrating the insulator filling the space between the two flat measurement electrodes. In the case where the measurement electrode is a rod-like or needle-like electrode, examples of the cell include a measurement cell having a branch channel that branches from a channel (main channel) through which a liquid flows and contacts the measurement electrode.

As still another aspect of the measurement cell for electrical conductivity detector of the present invention,
Two working electrodes installed in parallel,
Two measuring electrodes placed parallel to and between the two working electrodes, and
An insulator filling between the two working electrodes;
A flow path for flowing a liquid placed in contact with the two working electrodes and the two measuring electrodes;
The two measurement electrodes are installed at positions that are recessed with respect to the flow direction of the liquid in the flow path,
An example of the measurement cell for an electrical conductivity detector is that the length of the contact region between the measurement electrode and the flow path is sufficiently shorter than the distance between the two measurement electrodes and / or the inner diameter of the flow path that penetrates the insulator.

  In the measurement cell for an electrical conductivity detector of the present invention, an insulator is provided on the outside of the two working electrodes, one electrode on one side or a pair of electrodes on both sides, and / or located between the two measuring electrodes. It is further preferable that one or two electrodes are further installed on the outer surface and a predetermined voltage is applied, since the influence of leakage current flowing outside the flow path can be reduced.

  The electrical conductivity detector for liquid chromatography of the present invention is characterized in that it has two working electrodes and two measuring electrodes, and has a measuring cell in which current flows into and out of the measuring electrodes. Compared to a conventional measurement cell having two working electrodes and two measurement electrodes, the change in the current path due to the change in ion concentration is reduced. Therefore, compared with the conventional measuring cell with two working electrodes and two measuring electrodes, the output linearity when measuring a high concentration ionic solution is improved, and as a result, the linearity of the calibration curve is improved. A degree detector can be provided.

  In addition, the electrical conductivity detector of the present invention does not decrease the linearity of the calibration curve even if the flow path for flowing the liquid is shortened, so that the measurement cell can be downsized without reducing the inner diameter of the flow path. Can do. Therefore, it is possible to provide an electrical conductivity detector that does not have a problem of a peak spreading inside the measurement cell and that can be analyzed with a very small amount and high sensitivity.

  Furthermore, on the outer side of the two working electrodes of the measurement cell, one electrode on one side or a pair of electrodes on both sides is further installed, or on the outer surface of the insulator located between the two measurement electrodes of the measurement cell. If one or two electrodes are further installed, the influence of leakage current flowing outside the flow path can be reduced, so that an electrical conductivity detector capable of further high sensitivity / high accuracy analysis is provided. be able to.

The schematic diagram of the conventional electrical conductivity detector which has the measurement cell provided with two electrodes. The schematic diagram of the measuring cell used for the conventional electrical conductivity detector provided with two working electrodes and two measuring electrodes (patent document 1). The figure which shows the one aspect | mode of the electrical conductivity detector of this invention. The figure which shows the one aspect | mode of the electrical conductivity detector of this invention. The figure which shows the one aspect | mode of the electrical conductivity detector of this invention. The figure which shows the one aspect | mode of the electrical conductivity detector of this invention. The graph which shows the result of having measured KCl aqueous solution using the detector of FIG. 3 or FIG.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  A first embodiment of the electrical conductivity detector of the present invention is shown in FIG.

  The measuring cell (10) of the detector shown in FIG. 3 includes two working electrodes (12) and two flat plate measuring electrodes (13), and is between the working electrode (12) and the measuring electrode (13). And the space between the two measurement electrodes (13) is filled with an insulator (14). One of the two working electrodes (12) has a block shape including a joint for connecting to a pipe through which the liquid eluted from the separation column flows, and the other passed through the measuring cell (10). It has a block shape including a joint for connecting with a pipe for flowing the liquid eluted from the separation column to a waste liquid tank or another analyzer / analytical column. The two working electrodes (12) are provided with a flow path (15) for flowing the liquid eluted from the separation column. The flow path (15) includes two working electrodes (12), two measurement electrodes ( 13) and the insulator (14) are installed so as to penetrate in the coaxial direction so that the liquid eluted from the separation column flows into the measurement cell (10). The two measurement electrodes (13) are installed in a direction orthogonal to the direction in which the liquid eluted from the separation column flows. In addition, it is preferable that the measurement electrode (13) in FIG. 3 has a smaller contact area with the flow path (15), and the length of the contact area between the measurement electrode (13) and the flow path (15), that is, the measurement electrode (13). It is particularly preferable that the thickness of the flat plate used in the above is 0.1 mm or less.

  Among the detectors shown in FIG. 3, the differential amplifier (20) and the current detection amplifier (50) are amplifiers having a sufficiently high input impedance with respect to the liquid eluted from the separation column flowing through the measurement cell (10), for example, an amplifier. A instrumentation amplifier may be used.

  Among the detectors shown in FIG. 3, the voltage oscillation unit (30) is not particularly limited as long as the electrical conductivity can be measured, but when a sine wave transmission circuit having a frequency of about 1 kHz is used, the measurement cell (10) is provided. This is preferable because the influence of the polarization of the flowing liquid eluted from the separation column can be reduced. The oscillation amplitude of the voltage oscillation unit (30) is fed back so that the potential difference between the measurement electrodes becomes constant, so that the voltage across the current detector resistor (40) is a value proportional to the electrical conductivity of the electrolyte. It becomes.

  A second embodiment of the electrical conductivity detector of the present invention is shown in FIG. In FIG. 4, the configuration other than the measurement cell (10) is the same as that of the detector of FIG.

The measuring cell (10) of the detector shown in FIG. 4 includes two working electrodes (12) and two needle-shaped measuring electrodes (13), and an insulator is provided between the two working electrodes (12). (14) and the measurement electrode (13) is also covered with the insulator (14). One of the two working electrodes (12) has a block shape including a joint for connecting to a pipe through which the liquid eluted from the separation column flows, and the other passed through the measuring cell (10). It has a block shape including a joint for connecting with a pipe for flowing the liquid eluted from the separation column to a waste liquid tank or another analyzer / analytical column. The two working electrodes (12) are provided with a flow path (15) for flowing the liquid eluted from the separation column, and the flow path (15) includes two working electrodes (12) and an insulator (14). By installing so as to penetrate in the coaxial direction, the liquid eluted from the separation column flows into the measurement cell (10). Moreover, it installs so that the said flow path (15) and the end of two measurement electrodes (13) may contact. The two measurement electrodes (13) are installed so that their axes are orthogonal to the direction in which the liquid eluted from the separation column flows. In addition, the measurement electrode (13) in FIG. 4 is so preferable that the length of a contact region is small, and it is especially preferable that the contact area of a measurement electrode (13) and a flow path (15) shall be 0.01 mm < ² > or less.

  A third embodiment of the electrical conductivity detector of the present invention is shown in FIG. In FIG. 5, the configuration other than the measurement cell (10) is the same as that of the detector of FIG.

  The measuring cell (10) of the detector shown in FIG. 5 includes two working electrodes (12) and two flat measuring electrodes (13), and is between the working electrode (12) and the measuring electrode (13). And the space between the two measurement electrodes (13) is filled with an insulator (14). One of the two working electrodes (12) has a block shape including a joint for connecting to a pipe through which the liquid eluted from the separation column flows, and the other passed through the measuring cell (10). It has a block shape including a joint for connecting with a pipe for flowing the liquid eluted from the separation column to a waste liquid tank or another analyzer / analytical column. The two working electrodes (12) are provided with a flow path (15) for flowing the liquid eluted from the separation column. The flow path (15) includes two working electrodes (12), two measurement electrodes ( 13) and the insulator (14) so as to penetrate, and the liquid eluted from the separation column flows into the measurement cell (10). The two measurement electrodes (13) are installed in a direction orthogonal to the direction in which the liquid eluted from the separation column flows. The inner diameter of the flow path (15) passing through the two measurement electrodes (13) penetrates the insulator between the working electrode (12) and the measurement electrode (13) and between the two measurement electrodes (13). It is larger than the inner diameter of the flow path (15). Compared with a conventional measurement cell having two working electrodes and two measurement electrodes, the configuration described above reduces the current flow into and out of the individual measurement electrodes (13). Can be reduced. Note that the inner diameter of the flow path (15) passing through the measurement electrode (13) in FIG. 5 is larger than the inner diameter of the flow path (15) passing through the insulator (14) filling the gap between the two measurement electrodes (13). It is more preferable that the thickness of the flat plate used in the measurement electrode (13) is 1/2 or more. Furthermore, it is preferable that the measurement electrode (13) in FIG. 5 has a smaller contact area with the flow path (15), and the length of the contact area between the measurement electrode (13) and the flow path (15), that is, the measurement electrode (13). It is particularly preferable that the thickness of the flat plate used in the above is 0.1 mm or less.

  A fourth embodiment of the electrical conductivity detector of the present invention is shown in FIG. In FIG. 6, the configuration other than the measurement cell (10) is the same as that of the detector of FIG.

The measuring cell (10) of the detector shown in FIG. 6 includes two working electrodes (12) and two needle-shaped measuring electrodes (13), and an insulator is provided between the two working electrodes (12). (14) and the measurement electrode (13) is also covered with the insulator (14). One of the two working electrodes (12) has a block shape including a joint for connecting to a pipe through which the liquid eluted from the separation column flows, and the other passed through the measuring cell (10). It has a block shape including a joint for connecting with a pipe for flowing the liquid eluted from the separation column to a waste liquid tank or another analyzer / analytical column. The two working electrodes (12) are provided with a main channel (15) for flowing the liquid eluted from the separation column, and the main channel (15) passes through the two working electrodes (12) and the insulator (14). As a result, the liquid eluted from the separation column flows in the measurement cell (10). Further, a branch channel (16) for connecting one end of the two measurement electrodes (13) and the main channel (15) is also provided. The axes of the two measurement electrodes (13) and the branch channel (16) are installed so as to be orthogonal to the axis of the main channel (15). Compared with a conventional measurement cell having two working electrodes and two measurement electrodes, the configuration described above reduces the current flow into and out of the individual measurement electrodes (13). Can be reduced. In addition, it is more preferable that the length of the branch channel (16) in FIG. 6 is 1/2 or more of the outer diameter of the measurement electrode (13). Furthermore, the measurement electrode (13) in FIG. 6 is preferably as the contact region length is small, and the contact area between the measurement electrode (13) and the flow path (15) is particularly preferably 0.01 mm ² or less.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, these are one Embodiment of this invention, and do not limit this invention.

Example 1
Various concentrations of KCl aqueous solutions were measured using the electrical conductivity detector shown in FIG.

  In the detector shown in FIG. 3, the working electrode (12) and the plate measuring electrode (13) are made of 316 stainless steel (SUS316), and the insulator (14) is made of polytetrafluoroethylene (PTFE). The thickness of the insulator (14) filling between the two measurement electrodes (13) is 1.0 mm, and the thickness of the insulator (14) filling between the working electrode (12) and the measurement electrode (13) is 0.2 mm. The internal diameter of the flow path (15) which penetrates a working electrode (12), a measurement electrode (13), and an insulator (14) was 0.8 mm. The voltage oscillation unit (30) output a sine wave having a frequency of 1 kHz so that the amplitude between the measurement electrodes (13) is always constant at 1V.

  In the detector, the measurement cell (10) in which the thickness of the two measurement electrodes (13) is 0.012 mm, 0.1 mm, 0.2 mm, 0.5 mm, and 1.0 mm, and the two shown in FIG. Using a measuring cell composed of two electrodes, the detector output when a KCl solution of a known concentration was passed through the measuring cell (10) was measured.

  FIG. 7 shows the results of plotting the relationship between the KCl aqueous solution concentration and the detector output when the measurement cell is used. In FIG. 7, the horizontal axis indicates the KCl concentration (mM), and the vertical axis indicates the value obtained by normalizing the detector output so that the output of 1 mM is 1. Rather than a measurement cell consisting of two electrodes (bipolar electrode in FIG. 7, 10 in FIG. 1), a measurement cell consisting of two reference electrodes and two measurement electrodes (quadrupole electrode in FIG. 7, 10 in FIG. 3). However, the linearity of the detector output with respect to the KCl concentration was better. Further, the thinner the measurement electrode (13), the better the linearity of the detector output with respect to the KCl concentration. In particular, the thickness of the measurement electrode (13) is between the two measurement electrodes (13). When the thickness of the insulator (14) filling the surface and / or the inner diameter of the flow path (15) is 1/5 or less (0.2 mm or less), it was good.

  The electrical conductivity detector for liquid chromatography of the present invention has a reduced change in current path due to a change in ion concentration, as compared with a conventional detector. As a result, the output linearity when measuring a high concentration ionic solution is improved, and as a result, an electric conductivity detector with improved linearity of the calibration curve can be provided. Moreover, the electrical conductivity detector of the present invention can reduce the size of the measurement cell without reducing the inner diameter of the flow path. From the above, by using the above-mentioned apparatus, it is possible to perform analysis with a small amount and high sensitivity of ion chromatography.

DESCRIPTION OF SYMBOLS 10 Measurement cell 11 Electrode 12 Working electrode 13 Measuring electrode 14 Insulator 15 Flow path 20 Differential amplifier 30 Voltage oscillation part 40 Current detection resistor 50 Current detection amplifier 60 Voltage detection part 70 Electric force line

Claims (7)

Two working electrodes installed in parallel,
Two measuring electrodes placed parallel to and between the two working electrodes, and
An insulator filling between the two working electrodes;
A flow path for flowing a liquid, placed in contact with the two working electrodes and the two measuring electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
An electrical conductivity detector for liquid chromatography, characterized in that current flows into and out of the measurement electrode very little. Two working electrodes installed in parallel,
Two measuring electrodes placed parallel to and between the two working electrodes, and
An insulator filling between the two working electrodes;
A flow path for flowing a liquid, placed in contact with the two working electrodes and the two measuring electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
The length of the contact region between the measurement electrode and the flow channel in the measurement cell is sufficiently shorter than the distance between the two measurement electrodes and / or the inner diameter of the flow channel, for liquid chromatography Electrical conductivity detector. Two working electrodes installed in parallel,
Two flat measurement electrodes installed in a position parallel to and sandwiched between the two working electrodes;
Two insulators filling the gap between the working electrode and the measuring electrode;
An insulator filling between the two plate measuring electrodes;
A flow path for flowing liquid, penetrating the two working electrodes, the two plate measuring electrodes, and the three insulators;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
In the measurement cell, the length of the contact area between the flat plate measurement electrode and the flow path is the length of the contact area between the insulator and the flow path that fills the space between the two flat plate measurement electrodes and / or the flow path. An electrical conductivity detector for liquid chromatography, characterized by being sufficiently shorter than the inner diameter. The length of the contact area between the flat plate measurement electrode and the flow path is 1/5 of the length of the contact area between the insulator and the flow path filling the gap between the two flat plate measurement electrodes and / or the inner diameter of the flow path. The electrical conductivity detector according to claim 3, wherein: Two working electrodes installed in parallel,
Two rod-shaped or needle-shaped measuring electrodes installed at a position parallel to and sandwiched between the two working electrodes,
An insulator filling between the two working electrodes;
A flow path for flowing liquid, penetrating through the two working electrodes and the insulator, and in contact with one end of the two measurement electrodes;
In an electrical conductivity detector for liquid chromatography having a measuring cell comprising:
An electrical conductivity detector for liquid chromatography, wherein an outer diameter of the measurement electrode in the measurement cell is sufficiently shorter than an interval between the measurement electrodes and / or an inner diameter of the flow path. The electrical conductivity detector according to claim 2, further comprising a measurement cell having one electrode on one side or a pair of electrodes on both sides outside the two working electrodes. The electrical conductivity detector according to claim 2, further comprising a measurement cell further provided with one or two electrodes on an outer surface of an insulator located between the two measurement electrodes.

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