Suppressor formed of emulsified ion exchange resin

Abstract

To provide a suppressor continuously analyzed without restricting ion exchange capacity.SOLUTION: In an ion chromatograph consisting of at least an eluent 1, a pump 3 for sending the eluent, a sample injection mechanism 4 for injecting a sample and an analysis column 5, a method comprises: joining an emulsified suppression ion exchange resin to an elution solution from the analysis column at a fixed flow rate; passing a coil for mixing the emulsified ion exchange resin with the elution solution to reduce the electrical conductivity of the mixed fluid; and measuring the concentration change of a component separated by the analysis column by a conductivity detector 7.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a suppressor using a suspended ion exchange resin in ion chromatography.

Background Art

[0002] Suppressors in ion chromatography have been put into practical use in a plurality of forms. The most common form is the "membrane permeation suppressor" (see Fig. 1). In this method, the eluent is passed through one of two flow paths separated by an ion exchange membrane, and the regeneration liquid is fed to the other. Ions in the eluent are dialyzed and removed to the flow path on the regeneration liquid side chemically or by electrodialysis.

[0003] Since ion removal and regeneration are performed simultaneously, it is possible to perform measurements under a stable baseline even in long-term analysis. However, it also has the drawback that contamination of the ion exchange membrane is likely to occur and regular maintenance is required.

[0004] Also, the "column removal type (cartridge type, etc.)" is a method of reducing the background electrical conductivity by filling a mini column with an ion exchange resin and capturing the counter ions of the eluent with an ion exchange group. Since analysis and regeneration are performed in separate processes, it is said that noise generation due to regeneration does not occur and operation with low noise is possible. However, it is regarded as a drawback that "regeneration" for removing the captured ions by stopping the analysis becomes necessary because ion removal becomes impossible when the ion exchange group is saturated.

[0005] To compensate for this, a method has also been devised in which mini columns filled with a plurality of ion exchange resins are switched to perform analysis and regeneration in parallel (see Fig. 2). In addition, a method has been proposed in which the mini column filled with the ion exchange resin is replaced with a new one for each analysis (see Fig. 3) (Prior Art Document 1). Any "column removal type" suppressor has a drawback that there is a limit to the ion exchange capacity and it cannot cope with measurements with a long analysis time.

Prior Art Documents

Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-195301 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2011-53174 Patent Document 3: Japanese Unexamined Patent Application Publication No. 2018-9943

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made to solve the above problems, and provides a suppressor that has no restriction on ion exchange capacity and can perform continuous analysis.

Means for Solving the Problems

[0008] The present invention provides a method characterized in that, in an ion chromatograph including at least an eluent, a pump for feeding the eluent, a sample injection mechanism for injecting a sample, and an analytical column, an ion exchange resin for suppression in an emulsion state is caused to merge with an eluate from the analytical column at a constant flow rate, the eluate and the ion exchange resin in the emulsion state are passed through a coil for mixing them, after reducing the electric conductivity of the mixed fluid, a change in concentration of components separated by the analytical column is measured by a conductivity detector.

[0009] Further, the present invention provides an apparatus characterized in that, in an ion chromatograph including at least an eluent, a pump for feeding the eluent, a sample injection mechanism for injecting a sample, and an analytical column, an ion exchange resin for suppression in an emulsion state is caused to merge with an eluate from the analytical column at a constant flow rate, the eluate and the ion exchange resin in the emulsion state are passed through a coil for mixing them, after reducing the electric conductivity of the mixed fluid, a change in concentration of components separated by the analytical column is measured by a conductivity detector.

[0010] The coil for mixing the eluate from the analysis column and the ion exchange resin in emulsion state is not limited in terms of its material, but fluorine-based resins such as polytetrafluoroethylene (PTFE) and "inert materials" such as polyetheretherketone (PEEK) are suitable, and it is preferable to use PEEK which has high hardness and is difficult to deform.

[0011] Also, the volume (capacity) of the coil may be optimized according to the analysis column, eluent composition, salt concentration, flow rate of the eluent, etc., and does not specify the inner diameter, length, and shape. Generally, it is preferable to use one with an outer diameter of 1 / 16 inch which is commonly used in HPLC, and the inner diameter may be selected within a range where the ion exchange resin in emulsion state does not cause clogging and does not reduce the performance of the analysis column, but an inner diameter of 0.5 to 1.0 mm is preferable. Also, the form of the coil may be random, but by making it into a spiral shape of about 20 mmφ to 100 mmφ, the mixing property of the ion exchange resin for suppression and the eluate from the column is improved, the suppression effect is likely to be improved, and the storage property is also good, which is preferable.

[0012] The ion exchange resin for suppression may be the counter ion of the exchange group of the ion exchange resin used in the analysis column, and the ion exchange capacity only needs to be sufficient for the salt concentration and sample concentration of the eluent, and is not limited. Also, the ion exchange resin for suppression has a granular or crushed shape, and it is sufficient that the particle size is at least in the range of 5 to 150 μm.

[0013] Due to the relationship of specific gravity, the ion exchange resin for suppression will settle after a while even when it is put into pure water and stirred. Uniformity cannot be ensured in the settled state. Therefore, in the present invention, it is characterized in that a dispersant (additive) is added so that the ion exchange resin for suppression is adjusted to an emulsion state and a uniform state can be maintained. The dispersant (additive) needs to satisfy at least the following conditions.

[0014] First, it should be soluble in pure water and the suppressor gel can be easily dispersed. Second, it should not have an adverse effect on the performance of the detector used in ion chromatography when added to pure water. The adverse effect means, for example, not increasing the background when using a conductivity detector, and not having absorption in the wavelength region used when using an ultraviolet-visible detector. Also, it is important not to affect the suppression effect.

[0015] It is not easy to stably deliver the liquid in the state where the suppressor gel is dispersed (emulsion gel), and solving this problem is also one of the elements of the present invention.

[0016] As a result of intensive studies to achieve this object, it has been found that a nonionic surfactant is effective as a dispersant (additive). The nonionic surfactant does not have absorption in the ultraviolet absorption region from 220 nm to 380 nm, and may be one kind or a combination of two or more kinds selected from the following types of nonionic surfactants, and is not particularly limited. (i) Polymer of ethylene oxide with an average molecular weight of 1000 to 10000 (ii) Higher alcohol ethylene oxide adduct (iii) Polyoxyethylene fatty acid ester (fatty acid ethylene oxide adduct and polyethylene glycol fatty acid ester) (iv) Higher alkylamine ethylene oxide adduct and fatty acid amide ethylene oxide adduct (polyoxyethylene alkylamine and polyoxyethylene fatty acid amide) (v). Polypropylene glycol ethylene oxide adduct (Registered trademark Pluronic type nonionic surfactant, polyoxyethylene polyoxypropylene glycol) (vi) Fatty acid esters of glycerin and pentaerythritol (vii) Fatty acid esters of sorbitol and sorbitan (viii) Fatty acid esters of sucrose (ix) Alkyl polyglycoside (x) Fatty acid alkanolamide Among these, Bridge 35 (Japanese name), which has an average molecular weight of about 1200 and is also an adduct of higher alcohol and ethylene oxide, is particularly suitable. Japanese name: Bridge 35 Alternative Japanese name: Polyoxyethylene 23 lauryl ether English name: Brij 35 Alternative English name: Polyoxethylene lauryl ether CAS No.: 9002-92-0 The emulsion gel is in a state where the ion exchange resin is suspended in pure water. The method of stably feeding the liquid containing fine particles in the suspended state is limited. For example, in the case of the "plunger type" pump with a check valve generally used in HPLC, it is difficult to perform stable liquid feeding because the fine particles inhibit the operation of the check valve (see Figure 4).

[0017] Also, the "diaphragm type" pump using membrane expansion / contraction, etc. can relatively stably feed the liquid containing fine particles compared to the above-mentioned "plunger type" pump, but it has a low pressure resistance and is not suitable for use in the low flow rate range. Therefore, as a method of stably feeding the liquid containing fine particles, it is a pump of a type that sends out the fluid in the tube by the peristalsis of a soft tube, such as a sigoki pump, a tube pump, a roller pump, a peristaltic pump, etc. This method is suitable for feeding high-viscosity fluids because a check valve is not required, and it is also possible to feed fluids containing fine particles (see Figure 5).

[0018] Also, as a method of stably feeding the liquid containing fine particles, there is the "pressure feeding method by gas". As shown in Figure 6, the emulsion gel is stored in a sealable container, and a certain pressure is applied with air or an inert gas to extrude the emulsion gel. In this method, stable liquid feeding is possible even if fine particles are contained, but there is also a problem that it is difficult to grasp the actual liquid feeding flow rate.

[0019] In recent years, as a pump without a check valve, a pump classified as a plunger pump, which adds a rotational motion of a plunger to the reciprocating motion of the plunger, has been provided. Since this type of pump does not have a check valve, it is possible to pump high-viscosity fluids and fluids containing fine particles, and it is also possible to transfer gases.

[0020] The structure of this pump is schematically shown in FIG. 7. In a normal plunger pump, check valves are provided above and below the pump chamber, but this pump has a plurality of through ports instead of check valves. The plunger of a normal plunger pump is a smooth cylindrical shape, whereas this pump has one groove in the longitudinal direction of the smooth cylindrical plunger. In addition to linear drive, the plunger can also perform a rotational motion at the position of the through hole in the pump chamber. By aligning the groove of the plunger with the through port position in the pump chamber by rotational motion and sucking the plunger at that position, fluid is sucked from the port. Next, by aligning the groove of the plunger with another through port position by rotational motion and discharging the plunger at that position, fluid is discharged from the port. By performing this operation periodically, it is possible to suck from a specific through port and discharge to another through port.

[0021] Also, at least two or more through ports of this pump chamber can be arranged, and the suction port and the discharge port can be selected according to the purpose. It is possible not only to pump an emulsion gel containing fine particles, but also to wash the inside of the suppressor with pure water or replace it with air. FIG. 8 is a diagram schematically showing the operation of the plunger when there are six ports in the pump chamber, with port 6 as the suction port and port 1 as the discharge port. In addition, in order to make the rotational motion of the plunger easy to understand, a symbol ● is attached to the groove position. The pump for pumping the suppressor gel in the emulsion state in the present invention only needs to be able to stably pump the fluid in the above state, and is not limited to the above-described pump. In any pump type, in order to further ensure the uniformity of the emulsion gel, it is also effective to always stir with a magnetic stirrer / rotor.

Brief Description of the Drawings

[0022]

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Example

[0023] The effects of the present invention were verified by the following method. The ion chromatograph was composed of a built - type HPLC unit manufactured by Tosoh Corporation.

Example 1

[0024] In this example, verification was carried out using a method of separating various anions by "isocratic elution". The configuration is shown in Fig. 9. As the suppressor coil (14), a PEEK pipe with an inner diameter of 0.75 mm or 1.0 mm and a length of 700 cm was used in a coiled shape with a diameter of about 5 cm. For the purpose of eliminating the influence of the outside air temperature, the injected sample preheating coil (31), guard column (30), analytical column (5), and suppressor coil (14) were arranged in one column oven (6). The conditions for basic ion chromatography (anion analysis) are as follows. As the detector, a flow type cell of ES-51 manufactured by Horiba, Ltd. was used (see Fig. 10).

[0025] Anion Chromatography Analysis Conditions

Table 1

[0026] In this example, as the pump for suppressor gel liquid feeding, DP-11 manufactured by From Co., Ltd., a plunger pump without a check valve, was used. The structure of the pump is shown in Fig. 7.

[0027] This pump is composed of a pump chamber with six liquid passing ports at 60° intervals and a plunger capable of reciprocating linear drive and rotational motion. In addition, the plunger has a groove through which liquid can pass in the linear drive direction. In the case of a normal plunger type pump, check valves are arranged above and below the pump chamber, and as the plunger reciprocates, the liquid flows from the bottom to the top of the pump chamber. In the case of this pump, the groove of the plunger performs a suction / discharge operation in accordance with the groove position of the pump chamber. When the suction operation of the plunger is performed at the position of a specific liquid passing port, the fluid is sucked from that liquid passing port. Next, when the plunger is rotated to another port position and the plunger is made to perform a discharge operation, it is discharged to the said port. That is, since the suction port and the discharge port can be selected, liquid feeding is possible even without a check valve. In addition, since this pump has no check valve, it is possible to feed highly viscous fluids, fluids containing fine particles, and gases.

[0028] This pump was used as the liquid delivery mechanism for the suppressor gel in ion chromatography. Also, as described above, since the suction / discharge ports can be freely selected, there is also the advantage that the cleaning operation and replacement operation after measurement can be performed simultaneously.

[0029] In this example, the flow path arrangement of the suppressor gel liquid delivery pump was as follows (see Fig. 11). Port 1: Discharge port to the suppressor (coil) Port 2: Suction port for pure water Port 3: Not used (blocked by a stop plug) Port 4: Not used (blocked by a stop plug) Port 5: Suction port for air (a sintered filter is arranged for the purpose of preventing dust from mixing in) Port 6: Suction port for emulsion gel When delivering the emulsion gel, the emulsion gel is sucked from Port 6 and delivered to the suppressor through Port 1. That is, pull the plunger at Port 6 and rotate it counterclockwise by 60°, then push the plunger at Port 1. After that, rotate it clockwise by 60° and repeat the operation of pulling the plunger at Port 6, and the emulsion gel will be delivered (Fig. 12a, Fig. 14). The delivered emulsion gel merges with the eluate from the analytical column at the T-joint (39), is mixed in the suppressor coil, reduces the background of the eluent, and is led to the detector. This state becomes the flow path for actual analysis.

[0030] Also, after the actual analysis is completed, it is desirable to replace the inside of the flow path with pure water or air. This is to suppress troubles such as clogging of the piping due to the sedimentation of the gel when the emulsion state suppressor gel remains in the flow path for a long time. When cleaning the suppressor, pure water is pumped. Suction pure water from port 2 and pump it to the suppressor through port 1. That is, pull the plunger at port 2, rotate it 60°C clockwise, and push the plunger at port 1. Then, rotate it 60° counterclockwise and repeat the operation of pulling the plunger at port 2 to pump pure water (Figure 12b, Figure 15). The pumped pure water merges with the eluate from the analytical column at the T-joint (39), flushes the suppressor gel remaining in the suppressor coil, and cleans the area after the suppressor coil. At this time, the eluent can be in the pumping state or the pumping stop state.

[0031] Also, when replacing the air inside the suppressor, air is pumped. Suction air from port 5 and pump it to the suppressor through port 1. That is, pull the plunger at port 5, rotate it 120°C counterclockwise, and push the plunger at port 1. Then, rotate it 120°C clockwise and repeat the operation of pulling the plunger at port 5 to pump air (Figure 12c, Figure 16). The pumped air merges at the T-joint (39) to replace the air inside the suppressor coil. At this time, the eluent preferably has the pumping stopped state.

[0032] As described above, even when the inside of the suppressor is replaced with pure water or air, the emulsion gel remains in the suction pipe of the gel pump. When recovering this emulsion gel, reverse the pure water flow into the emulsion gel container. Suction pure water from port 2 and pump it to the emulsion gel container through port 6 (Figure 13a, Figure 17). That is, pull the plunger at port 2, rotate it 120° clockwise, and push the plunger at port 6. Then, rotate it 120° counterclockwise and repeat the operation of pulling the plunger at port 2 to recover the emulsion gel in the suction pipe into the container.

[0033] When it is desired to replace the air in the emulsion gel suction pipe with air in the same manner, the air is made to flow backward into the emulsion gel container. Air is sucked from port 5 and the liquid is sent to the emulsion gel container through port 6. That is, the plunger is pulled at port 5 and rotated counterclockwise by 60°, and the plunger is pushed at port 6. Thereafter, by repeating the operation of rotating 60° clockwise and pulling the plunger at port 5, the inside of the suction pipe is replaced with air (Figs. 13b, 18).

[0034] The selection of the dispersant (additive) for the suppressor gel for ion exchange will be described. In this example, polyoxyethylene 23 lauryl ether (hereinafter referred to as Bridge 35, Brij35) was used as the dispersant (additive). Bridge 35 has the structure of Chemical Formula 1. Since it does not have a carbonyl group, a carboxy group, multiple bonds or an aromatic ring, it is a substance that does not have ultraviolet-visible absorption. Fig. 20 shows the ultraviolet absorption spectra of 0.1, 1, and 10% aqueous solutions of Bridge 35. Absorption cannot be confirmed even with 10% Bridge 35 in the ultraviolet region of 210 nm or more, which is the usually used region. Since it is not dissociated and does not have a carboxy group or the like, it can be presumed to be a surfactant with low conductivity. Table 2 shows the main physical properties and hazards. It is highly safe, has excellent solubility in water and the like, and is suitable as a dispersant (additive) for the suppressor gel for ion exchange.

[0035] [Chemical formula]

[0036] Physical properties of Bridge 35 (extracted from SDS) [Table 2]

[0037] First, the dispersibility of the "Bridge 35" selected above in the gel for ion exchange was verified. The composition of the emulsion gel for ion exchange is as shown in Table 3.

[0038] Suppressor emulsion gel and suppression conditions

Table 3

[0039] In the case without an additive (pure water), gel sedimentation starts within less than 5 minutes after adjustment and is completely sedimented in about 15 minutes. When the "dispersant (additive)" of the present invention is added, the sedimentation rate is significantly slowed down, and a well - dispersed state can be maintained even after 30 minutes.

[0040] When feeding the gel for ion exchange, in the state after 5 minutes without an additive (Fig. b), stable feeding is difficult with any form of feeding mechanism. Even if feeding is possible, gel sedimentation occurs immediately, and obstacles such as clogging occur in the feeding channel.

[0041] When the "dispersant (additive)" of the present invention is added, the time during which the ion - exchange gel can be dispersed can be significantly extended. Even in the state after 30 minutes (Fig. f), stable feeding is possible by using a feeding mechanism in the form of a peristaltic pump, a gas - pressure feeding method, or a plunger - type pump without a check valve as described above. Also, a more stable emulsion state can be maintained by constantly stirring with a stirrer / magnetic stirrer, etc., and suitable feeding can be performed.

[0042] Next, the suppression effect was verified when the bridge 35 adjusted above was used as a dispersant (additive). As the pump for feeding the emulsion gel, the aforementioned check - valve - less plunger - type pump was used (the emulsion gel was sucked from port 6 and fed to the suppressor through port 1). The suppression conditions and the like are as shown in Table 3.

[0043] Figure 22 shows the difference in conductivity during the passage of the suppressor emulsion gel. Without suppression (no emulsion gel liquid feeding), the background conductivity is 1210.34 μS / cm, while with suppression (emulsion gel liquid feeding), it decreases to 24.91 μS / cm. Also, Figure 23 shows the baseline fluctuations when sulfate ions are injected with "without suppression" and "with suppression". Figure a is the case with suppression, and Figure b is the case without suppression. A peak of sulfate ions can be confirmed around 21.6 minutes with suppression, but it cannot be detected at all without suppression. From this, it is proven that the suppression effect by this method is sufficient. Also, Figure 24 shows the results of measuring multiple ions. Figure a is the result of measuring fluorine, chlorine, nitrite, bromine, phosphate, and sulfate ions individually, and Figure b is the result of measuring the mixture. From this, it can also be seen that the suppression effect by this method is sufficient and does not affect separation.

[0044] Next, verification was conducted regarding the reproducibility (n = 5) of the present invention. As the ion species, a mixture of fluorine, nitrite, and bromine ions was used. Figure 25 is a figure in which chromatograms obtained from 5 measurements are overlapped. Table 4 and Figures 26 and 27 show the variations in the elution time and area value of each peak. As can be seen from the figures and tables, no significant change is observed in the chromatogram in 5 measurements.

[0045] Also, a Cv% of about 0.2% in terms of elution time and a Cv% of about 2% in terms of area are obtained, which is good.

[0046] Measurement reproducibility

Table 4

[0047] Figure 28 shows the calibration curves for each ion, and Table 5 shows the measurement results. As can be seen from the figure, the area value is proportional to the concentration, and there is no problem with the response. For fluoride ions and sulfate ions, they can be approximated by a linear equation that approximately passes through the origin. Regarding nitrite ions, although there is some distortion and the error becomes large when approximated by a linear equation passing through the origin, a good calibration curve can be obtained with a quadratic equation passing through the origin, and there is no particular problem.

[0048] Linearity (area value) [Table 5] The present invention is a method using a suppressor gel for counter ions. Different from the conventional suppressor filled with a counter ion suppressor gel in a "mini column", the fact that it can be used continuously is also one of the great effects. When using a suppressor filled with a conventional counter ion suppressor gel in a "mini column", depending on the conductivity of the eluent used, when the ion exchange groups become saturated, measurement becomes impossible. Table 5 shows the measurement limits of the "gel exchange type suppressor" used in the ion chromatograph IC-8100 manufactured by Tosoh Corporation (a partial extract from the instruction manual). For example, under conditions close to those of this example, Analysis column: TSKgel SuperIC-AZ Eluent: 7.1 mM NaHCO 3 +1.0 mM Na 2 CO 3 the runtime is specified as 28 minutes. This means that a stable suppression effect can be obtained for 28 minutes (the shaded part in Table 6).

[0049] When performing long-term measurements, as shown in Figure 31, it is necessary to replace the suppressor gel during the analysis. The "↓" part in the figure indicates the timing of replacing the suppressor gel.

[0050] Recommended values for flow rate and runtime [Table 6] The method of the present invention uses a suppressor gel for counter ions similar to the aforementioned "gel exchange suppressor", and the ability to perform continuous measurements is also a major feature. Figure 29 shows the measurement results over a long period of time. Figure a shows the results of measuring a mixture of fluorine, nitrous acid, and sulfate ions three times in a row, and Figure b shows the results of measuring a mixture of bromine, sulfate ions, and fumaric acid. It can be seen that the suppression effect can be maintained even in a measurement over a long period of 70 minutes like this.

Example 2

[0051] In Example 1, it was carried out by the "isocratic elution method" in which the eluent composition is constant, but in Example 2, it was carried out by the "gradient elution method" in which the eluent composition is changed so that the elution power gradually increases. The system configuration is shown in Figure 32.

[0052] Basically, it is the same as Example 1, but one more liquid delivery pump was added to make a configuration capable of performing a high-pressure gradient. The suppression conditions and the like are the same as those in Example 1. Table 7 shows the analysis conditions, and Table 8 shows the gradient conditions.

[0053] Anion chromatography analysis conditions

Table 7

[0054] Gradient conditions

Table 8

[0055] Thus, even in the case of "gradient elution" where the background (conductivity) of the eluent is different, it can be measured by this method.

[0056] Elution time

Table 9

[0057] In the examples, by using a 6-port non-return valve plunger pump, processes such as feeding the suppression emulsion gel, cleaning the suppressor (coil), and recovering the suppression gel could be realized with a single liquid feeding mechanism. If the same multiple processes were to be carried out with other liquid feeding mechanisms, as shown in Fig. 35, it would be necessary to arrange a "three-way switching valve (40)" for switching to pure water on the suction side of the emulsion gel feeding pump and also add a mechanism for pumping air or an inert gas, which would complicate the structure. Furthermore, the increase in voids around the emulsion gel feeding pump increases the probability of various troubles, which is undesirable.

[0058] In this example, by using a "6-port non-return valve plunger pump", it was verified that the suppression gel in an emulsion state could be fed, the background of the eluent could be reduced, and ion chromatography could be performed. Also, since the "6-port non-return valve plunger pump" is equipped with ports for feeding pure water and ports for feeding air in addition to the suppression gel, as shown in Fig. 30, after performing the analysis, pure water can be fed to clean the flow path, and then air can be fed to replace the inside of the flow path with air. Thus, the entire process from the analysis operation to the stop operation can be realized with a single unit.

[0059] In this example, Bridge 35 was added and used as a dispersant at a ratio of 10%, but there is no particular limitation on the concentration. A range of 2 to 20% is suitable and a range of 5 to 10% is preferred, as it can disperse the ion exchange resin for suppression well, the conductivity after suppression decreases sufficiently, and the viscosity does not increase extremely. Figure 21 is a diagram comparing the chromatogram when Bridge 35 is added at a ratio of 5% as a dispersant with the baseline. It can be seen that reducing the concentration of Bridge 35 has no effect on the results.

[0060] In addition, polyethylene glycol (PEG), which is one of the polymers of ethylene oxide, is also effective as a dispersant. There are many commercially available polyethylene glycols with different molecular weight ranges, and their physical properties such as solubility and viscosity vary depending on the molecular weight. However, polyethylene glycol 4000 (PEG4000) with an average molecular weight of 2700 to 3300 is effective as a dispersant. Table 10 shows the physical properties of PEG4000 for reference (quoted from Fuji Film Wako Pure Chemical SDS).

[0061] PEG4000 Physical Properties

Table 10

Explanation of Symbols

[0062] 1. Eluent 2. Degassing device 3. Liquid delivery pump 4. Sample injection mechanism 5. Analytical column 6. Column thermostat 7. Detector 8. Membrane suppressor 9. Suppression column 10. Regenerant 11. Suppression emulsion gel liquid delivery pump 12. Switching valve 13. Suppression emulsion gel 14. Suppression coil 15. Check valve-less plunger pump 16. Plunger 17. Pump head 18. Pump chamber 19. Motor 20. Screw 21. Suppression valve 22. Suppression gel 23. Pure water 24. Liquid delivery pump (suppression gel) 25. Pressure regulating valve 26. Rotor 27. Magnetic stirrer 28. Roller 29. Tube 30. Guard column 31. Preheat coil 32. Groove 33. Plunger 34. Suction side check valve 35. Discharge side check valve 36. Pump chamber 37. Sintered filter 38. Stop plug 39. T-joint 40. Three-way switching valve 41. Eluent A 42. Eluent B 43. Degassing device (eluent A) 44. Degassing device (eluent B) 45. Liquid delivery pump (eluent A) 46. Liquid delivery pump (eluent B) 47. Liquid delivery pump (regenerant) 48. Electrode part

Claims

1. In an ion chromatograph comprising at least an eluent, a pump for feeding the eluent, a sample injection mechanism for injecting a sample, and an analytical column, an ion exchange resin for suppression in an emulsion state is caused to merge into the eluate from the analytical column at a constant flow rate, the eluate and the ion exchange resin in the emulsion state are passed through a coil for mixing them to reduce the electric conductivity of the mixed fluid, and then a method characterized by measuring a change in the concentration of components separated by the analytical column with a conductivity detector.

2. In an ion chromatograph comprising at least an eluent, a pump for feeding the eluent, a sample injection mechanism for injecting a sample, and an analytical column, an ion exchange resin for suppression in an emulsion state is caused to merge into the eluate from the analytical column at a constant flow rate, the eluate and the ion exchange resin in the emulsion state are passed through a coil for mixing them to reduce the electric conductivity of the mixed fluid, and then an apparatus characterized by measuring a change in the concentration of components separated by the analytical column with a conductivity detector.

3. The method according to claim 1, wherein the ion exchange resin for suppression has a granular or crushed shape and a particle size of 5 to 150 μm.

4. The apparatus according to claim 2, wherein the ion exchange resin for suppression has a granular or crushed shape and a particle size of 5 to 150 μm.

5. The method according to claim 1, wherein the dispersant for making the ion exchange resin for suppression into an emulsion state is a nonionic surfactant having no absorption in the ultraviolet absorption region from 220 nm to 380 nm in a state where it is added to pure water.

6. The apparatus according to claim 2, wherein the dispersant for making the ion exchange resin for suppression into an emulsion state is a nonionic surfactant having no absorption in the ultraviolet absorption region from 220 nm to 380 nm in a state where it is added to pure water.

7. The dispersant is (i) a polymer of ethylene oxide having an average molecular weight of 1000 to 10000 (ii) a higher alcohol ethylene oxide adduct (iii) a polyoxyethylene fatty acid ester (fatty acid ethylene oxide adduct and polyethylene glycol fatty acid ester) (iv) a higher alkylamine ethylene oxide adduct and a fatty acid amide ethylene oxide adduct (polyoxyethylene alkylamine and polyoxyethylene fatty acid amide) (v) Polypropylene glycol ethylene oxide adduct (Pluronic type nonionic surfactant, polyoxyethylene polyoxypropylene glycol) (vi) Fatty acid esters of glycerin and pentaerythritol (vii) Fatty acid esters of sorbitol and sorbitan (viii) Fatty acid esters of sucrose (ix) Alkyl polyglycoside (x) Fatty acid alkanolamide The method according to claim 5, which is at least one selected from the group consisting of.

8. The dispersant is (i) Polymer of ethylene oxide having an average molecular weight of 1000 to 10000 (ii) Higher alcohol ethylene oxide adduct (iii) Polyoxyethylene fatty acid ester (fatty acid ethylene oxide adduct and polyethylene glycol fatty acid ester) (iv) Higher alkylamine ethylene oxide adduct and fatty acid amide ethylene oxide adduct (polyoxyethylene alkylamine and polyoxyethylene fatty acid amide) (v) Polypropylene glycol ethylene oxide adduct (Pluronic type nonionic surfactant, polyoxyethylene polyoxypropylene glycol) (vi) Fatty acid esters of glycerin and pentaerythritol (vii) Fatty acid esters of sorbitol and sorbitan (viii) Fatty acid esters of sucrose (ix) Alkyl polyglycoside (x) Fatty acid alkanolamide The apparatus according to claim 6, which is at least one selected from the group consisting of.

9. A method characterized in that the liquid feeding mechanism for merging the ion exchange resin for suppressing the emulsion state at a constant flow rate is a liquid feeding mechanism without a check valve.

10. The liquid feeding mechanism according to claim 9 is composed of a pump chamber having two or more through holes and a plunger in a liquid-tight state in the pump chamber. The plunger has grooves in the horizontal direction, and the plunger reciprocates and rotates in the pump chamber so that the grooves of the plunger stop at the positions of the through holes provided in the pump chamber. A plunger type pump without a check valve.

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