JPH06213882A - Ion chromatograph - Google Patents

Abstract

PURPOSE:To solve problems of diffusion of a sample and stability of temperature and to obtain a signal with stable conductivity by providing a cell of a conductivity detector immediately after the suppresser of ion chromatograph. CONSTITUTION:A sample is injected from a sample injection valve 3. A sample loop 8 at this time is as shown by a solid line. A certain amount of sample is stored at the sample loop 8 mounted to the sample injection valve 3 and a surplus is unloaded. An eluent is sent from a pump 2 to an isolation column 4. When the sample loop 8 of the sample injection valve 3 is switched as shown by a broke line, the sample stored in the sample loop 8 is introduced to the isolation column 4, where ion constituent within the sample is isolated and further the eluent is neutralized by a suppresser 5, and the conductivity value (background) of the eluent is reduced. Then, the conductivity of ion within the sample liquid is detected by a cell 21 of a conductivity detector 20 which is provided within an ELOUT joint 12 of the suppresser 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an ion chromatograph for analyzing a sample liquid by separating the ions in the sample liquid, chromatographically separating the ions in a column, and detecting the ions with a conductivity detector. And, more particularly, to improvements in conductivity detectors.

[0002]

2. Description of the Related Art Generally, the following two types of conductivity detectors are known for use in ion chromatography. That is, the cell part and the electric circuit as one integrated detector,
Type with integrated display The electric circuit and display circuit are externally arranged, and in the non-suppressed ion chromatograph, only the cell part is kept in the thermostatic chamber containing the separation column. In the case of a type in which only the cell part is placed in a thermostatic chamber containing a suppressor

[0003]

However, the conductivity detector having the above structure has the following problems. Sample diffusion problem In the ion chromatograph, the conductivity detector and the separation column (suppressor) are connected by a pipe with a small inner diameter. The sample exiting the separation column (suppressor) is sent to the cell part of the conductivity detector through the pipe, but diffusion occurs by all means while passing through the pipe.

At present, the reason why the inner diameter of the pipe is made thin and the cell part is arranged in the same thermostatic chamber as the separation column (suppressor) is to prevent this diffusion as much as possible. Column size is inner diameter φ 4.6 mm, total length is 75 ~ 150 mm
In a system in which the flow rate of the eluent is 1 ml / min, the pipe length between the separation column (suppressor) and the cell can be reduced by using a pipe with an inner diameter of φ0.3 mm. Up to several tens of centimeters, the influence of diffusion in the pipe on the separation of chromatograms is small, but if it exceeds that, it becomes a problem.

Furthermore, for the purpose of high-speed and high-sensitivity analysis by suppressing the diffusion of the sample, the semi-micro IC (the injection volume of the sample, the volume of the column, and the flow rate of the liquid sent by the pump are suppressed to ½ to 1/10 or less). Ion chromatograph) and micro IC
In the (ion chromatograph), if the above-mentioned pipe is used between the separation column or suppressor and the conductivity detector, the diffusion of the sample is large and the separation of the chromatogram becomes poor, resulting in a semi-micro IC or micro IC. Can not exert the performance of.

Further, not only the piping of the pipe but also the diffusion of the sample in the stagnation part of the joint between the separation column or suppressor and the cell of the conductivity detector cannot be ignored. Cell temperature stability issues Conductivity detectors are extremely temperature sensitive, so even small temperature fluctuations in the temperature of the liquid entering the cell or the ambient temperature can change the conductivity signal, resulting in a chromatogram. Appears as noise. Also, since the detection sensitivity is determined by the S / N ratio,
Even if the output signal with respect to the concentration of the detector is the same, the smaller the noise, the higher the detection sensitivity.

The rate of change in conductivity with temperature increases as the conductivity value of the liquid increases. In the case of ion chromatography, in order to separate an ionic sample using a separation column containing an ion exchange resin, an eluent with a strong ionic property is inevitably required, and as a result, the conductivity value of the eluent is high. Become.

By the way, in the case of a non-suppressed type ion chromatograph, after the eluent and the sample have left the separation column, they enter the cell through a pipe, so that the pipe is inevitably affected by the ambient temperature and the detector The temperature of the incoming sample changes slightly. The fluctuation of the conductivity value due to this temperature fluctuation appears as noise in the signal of the detector.

Further, in the case of the suppressed type ion chromatograph, it has a role of lowering the conductivity value of the eluent after the separation by the column, that is, the conductivity background, by utilizing the ion exchange reaction. It is not possible to lower the conductivity value. Therefore, compared with the non-suppressed type ion chromatograph, the conductivity value has less fluctuation, but the conductivity value still fluctuates due to the fluctuation of the ambient temperature.

Therefore, in order to reduce the temperature change after coming out of the separation column or suppressor, try putting the separation column or suppressor and the cell part of the detector in the same thermostatic chamber, or by using an integrated detector. When the separation column and the cell are separated, a preheating mechanism is provided to keep the temperature of the liquid entering the cell at a constant temperature in advance. By doing so, the temperature stability is improved, but the structure becomes complicated because an additional preheating mechanism or the like is required. Further, there is a limit that can be stabilized in order to control the temperature that has once changed with the ambient temperature.

The present invention has been made in view of the above problems, and an object thereof is to solve the problems of sample diffusion and temperature stability, and to obtain an ion chromatograph with high sensitivity and stable conductivity signal. To provide a graph.

[0012]

In order to solve the above-mentioned problems, the present invention according to claim 1 conveys a predetermined amount of sample liquid as an eluent and injects it into a separation column filled with an ion exchange resin,
In an ion chromatograph in which ions in the sample solution are detected by a conductivity detector via a suppressor that separates ions in the sample solution and neutralizes the eluent, the conductivity detection is performed immediately after the suppressor. The cell of the vessel is arranged.

According to a second aspect of the present invention, a predetermined amount of the sample liquid is carried as an eluent and injected into a separation column filled with an ion exchange resin to separate the ions in the sample liquid,
In an ion chromatograph for detecting ions in the sample liquid with a conductivity detector, a cell of the conductivity detector is arranged immediately after the separation column.

[0014]

In the ion chromatograph according to the first and second aspects of the invention, the liquid discharged from the separation column (suppressor) immediately enters the cell of the conductivity detector to prevent the diffusion of the sample and the temperature change.

[0015]

Embodiments of the present invention will be described with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. 1 is a block diagram of the ion chromatograph of the first embodiment, FIG. 2 is a block diagram of the suppressor in FIG. 1, and FIG. 3 is an exploded perspective view of the suppressor in FIG.

In FIG. 1, 1 is an eluent tank for storing the eluent, and 2 is an eluent pump for pumping the eluent.
Reference numeral 3 is a sample injection valve that collects a predetermined amount of the sample liquid and conveys the collected sample liquid to the separation column 4 described later by the eluent from the eluent pump 2.

A separation column 4 is filled with an ion exchange resin and separates and elutes each ion contained in the sample liquid. A suppressor 5 neutralizes the eluent flowing out from the separation column 4 and lowers the conductivity value (background) of the eluent.

Reference numeral 6 denotes a removing solution tank for storing a removing solution for regenerating the suppressor 5, and 7 denotes a pump for pumping the removing solution to the suppressor 5. In this embodiment, the separation column 4 and the suppressor 5 are arranged in the constant temperature bath 7.

Next, the suppressor 5 will be described with reference to FIGS. 2 and 3. 10 is an ELIN joint 11 for the eluent inlet to the suppressor 5 and an ELOUT joint 1 for the eluent outlet
An upper plate provided with 2 and 11 is a lower plate.

Reference numeral 13 is an SV flow passage block in which an SV flow passage 13a through which the removing liquid flows is formed on the lower plate 11 side surface. Also, this SV flow path block 13 has an ELIN joint 11
An ELIN hole 13b connected to the ELOUT joint 12 and an ELOUT hole 13c connected to the ELOUT joint 12 are formed.

Between the SV channel 13a and the lower plate 11, from the SV channel block 13 side, the ion exchange membrane 14, the EL channel sheet 15 through which the eluent flows, the ion exchange membrane 16 and
The SV flow path plates 17 are stacked. The ion exchange membrane 14 has an ELIN hole 14 connected to the ELIN hole 13b.
a, ELIN hole 14b connected to ELOUT hole 13d, and SV
SVOUT hole 14c connected to the outlet side of the flow path 13a, and SVOUT
An SVOUT hole 14d connected to the inlet side of the flow path 13a is formed. The EL channel sheet 15 has an EL channel 15a.
, SVOUT hole 15b connected to SVOUT hole 14c, and SVI
An SVIN hole 15c connected to the N hole 14d is formed. The ion exchange membrane 16 has an SVOUT hole 16a connected to the SVOUT hole 15b and an SVIN hole connected to the SVIN hole 15c.
The hole 16b is formed. The SV flow path plate 17 is formed with an SV flow path 17a that connects the SVOUT hole 16a and the SVIN hole 16b. Then, these upper plate 10, SV channel block 13, ion exchange membrane 14, EL
Channel sheet 15, ion exchange membrane 16, SV channel plate 1
7 and the lower plate 11 are integrated by using a screw 18.

A conductivity detector 20 is provided in the ELOUT joint 12.
Cell 21 is provided. This cell 21 has an electrode 2
2, 23, a spacer 24 arranged between these electrodes 22 and 23 for maintaining a constant distance between the electrodes, and these electrodes 2
2, 23, and a guide 25 having a spacer 24 accommodated therein. Then, as shown in FIG. 1, the electric circuit 26 and the display unit 27 of the conductivity detector 20 are arranged outside.

Next, the operation of the above configuration will be described. The sample is injected from the sample injection valve 3. At this time, the sample loop 8 is in a solid line. The sample is stored in the sample loop 8 attached to the sample injection valve 3 in a fixed amount, and the excess amount is discharged. The eluent is sent from the pump 2 to the separation column 4.

When the sample loop 6 of the sample injection valve 3 is switched to the broken line state, the sample stored in the sample loop 8 is introduced into the separation column 4, where the ionic components in the sample are separated and the suppressor 5 is further added. Neutralizes the eluent and lowers the conductivity value (background) of the eluent. Then, the cell 21 of the conductivity detector 20 provided in the ELOUT joint 12 of the suppressor 5 detects the conductivity of the ions in the sample liquid.

According to the above construction, the conductivity of ions in the sample liquid is detected immediately after the outlet of the suppressor 5, whereby diffusion in the pipe and the joint portion of the pipe can be prevented.

Further, since the separation column 4, the suppressor 5 and the cell 21 of the conductivity detector 20 are arranged in the thermostat, there is no temperature change. Therefore, a highly sensitive and stable conductivity signal can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram of the ion chromatograph of the second embodiment, and FIG. 5 is an enlarged sectional view of the outlet joint in FIG. In this example, the ion chromatograph of the first example was a suppressed type ion chromatograph, whereas it was a non-suppressed type ion chromatograph. The reference numerals are given and the description thereof is omitted.

In this embodiment, the outlet joint 3 of the separation column 4 is used.
As in the first embodiment, the cell 41 of the conductivity detector 40 is provided in 0. This cell 41 has electrodes 42,
43, a spacer 44 arranged between these electrodes 42, 43 for maintaining a constant distance between the electrodes, and these electrodes 4
2, 43 and a spacer 45 are contained in the guide 45.

Next, the operation of the above configuration will be described. The sample is injected from the sample injection valve 3. At this time, the sample loop 8 is in a solid line. The sample is stored in the sample loop 8 attached to the sample injection valve 3 in a fixed amount, and the excess amount is discharged. The eluent is sent from the pump 2 to the separation column 4.

When the sample loop 6 of the sample injection valve 3 is switched to the broken line state, the sample stored in the sample loop 8 is introduced into the separation column 4, where the ionic components in the sample are separated and the separation column 4 The conductivity of the ions in the sample liquid is detected by the cell 41 of the conductivity detector 40 provided in the outlet joint 30.

According to the above structure, the conductivity of the ions in the sample liquid is detected immediately after the outlet of the separation column 4, so that the diffusion in the pipe and the joint portion of the pipe can be prevented.

Further, since the separation column 4 and the cell 21 of the conductivity detector 20 are arranged in the constant temperature bath, there is no temperature change. Therefore, a highly sensitive and stable conductivity signal can be obtained.

The present invention is not limited to the above embodiment. In the above-mentioned two examples, the explanation was made by using a normal liquid chromatograph, but in addition, semi-micro LC, micro LC
It goes without saying that it can also be applied to.

[0034]

As described above, according to the present invention, by disposing the cell of the conductivity detector immediately after the outlet of the separation column or the suppressor, the problems of sample diffusion and temperature stability are solved. It is possible to realize an ion chromatograph with high sensitivity and a stable conductivity signal.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ion chromatograph according to a first embodiment.

FIG. 2 is a configuration diagram of a suppressor in FIG.

FIG. 3 is an exploded perspective view of the suppressor in FIG.

FIG. 4 is a configuration diagram of an ion chromatograph according to a second embodiment.

5 is an enlarged cross-sectional view of the outlet joint in FIG.

[Explanation of symbols]

 4 Separation column 5 Suppressor 20,40 Conductivity detector 21,41 cell

Claims (2)

[Claims] 1. A predetermined amount of sample liquid is conveyed by an eluent,
It is injected into a separation column (4) filled with an ion exchange resin, the ions in the sample solution are separated, and a conductivity detector (2) is passed through a suppressor (5) for neutralizing the eluent.
0) in the ion chromatograph for detecting ions in the sample liquid, the conductivity detector (2) is provided immediately after the suppressor (5).
An ion chromatograph characterized in that the cell (21) of 0) is arranged. 2. A predetermined amount of sample liquid is conveyed by an eluent,
In an ion chromatograph for injecting into a separation column (4) filled with an ion exchange resin, separating ions in the sample liquid, and detecting ions in the sample liquid with a conductivity detector (40), Immediately after the separation column (4), the conductivity detector (4
An ion chromatograph characterized in that the cell (41) of 0) is arranged.