JPH01232260A - Flow analysis of chloride ion in caustic alkali - Google Patents

Abstract

PURPOSE:To easily or exactly measure the concn. of trace chloride ion in a sample alkaline soln. by executing the neutralization reaction of the above- mentioned soln. by an H type anion exchange resin, the adsorption of the trace chloride ions by an anion exchange resin and the detection and determination of the chloride ions by a halide ion selective electrode. CONSTITUTION:The sample soln. is passed through the H type anion exchange resin-packed column and is subjected to the neutralization treatment; thereafter, the soln. is passed through the anion exchange resin-packed preenriching column where the trace chloride ions are adsorbed to the resin. The soln. contg. the chloride ions eluted by the eluate is then passed through the anion exchange resin-packed column. The separated chloride ions are detected and determined by using the halide ion selective electrode. A series of the operations are carried out within the system of the flow injection analysis. The analysis operations are thereby simplified and speeded up and the problem of stain in the pretreatment operation is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for determining trace chloride ions in concentrated high purity caustic solutions.

(Prior art and issues to be solved) In recent years, the required quality of caustic alkali used in IC manufacturing processes in the electronics industry and purification equipment for nuclear reactor primary cooling water has become stricter, and the chloride content has also increased to 48% by weight, for example. % caustic alkali standard, a value of ippm or less is required.

As methods for analyzing chloride ions in caustic alkali, various titration methods and colorimetric methods have been widely used. However, the titration method cannot be expected to provide sufficient sensitivity for the trace measurement aimed at by the present invention. Although the colorimetric method has sufficient sensitivity, the neutralization operation performed in the pretreatment stage cannot be performed on a blank solution with a different pH under the same conditions as the sample solution, so it was used for neutralization. It is difficult to accurately subtract and correct the amount of chloride ions contained in acids, and since it is affected by salt concentration, variations in the alkali concentration of the sample will appear as variations in the coloring state, resulting in fluctuations in measured values. It has the disadvantage of being large. This becomes a problem as the chloride ion concentration in the sample becomes minute.

(Object of the Invention) In view of the above points, the inventors conducted extensive studies with the aim of obtaining a simple and accurate method for measuring trace chloride ion concentration.

As a result, we discovered that the above objective could be fully achieved by performing a neutralization operation in the pretreatment stage using an H-type cation exchange resin and incorporating a series of analysis operations into a flow analysis method including ion chromatography. This has led to the completion of the present invention.

(Structure of the Invention) The present invention is a method for measuring trace amounts of chloride ions in a high-purity caustic alkaline solution. pass through a pre-concentration column to adsorb trace chloride ions,
Next, the solution containing chloride ions eluted with the eluent is passed through a separation column packed with anion exchange resin, and the separated chloride ions are detected and quantified using a halide ion-selective electrode. This is a flow analysis method characterized by being carried out within an injection analysis system.

The flow injection analysis method is known per se, and involves continuously passing sample solutions and necessary analytical drug solutions into thin tubes to perform various reactions and separations, and using a detector installed at the end to perform rapid detection. This is the method of analysis.

The method of the present invention takes advantage of the characteristics of this system to perform a neutralization reaction of an alkaline sample solution using an H-type cation exchange resin, adsorption of trace chloride ions by an anion exchange resin, and a halide ion selective electrode for chloride ions. By carrying out detection and quantification using this method, it is possible to simplify and speed up the analysis operation and at the same time solve the problem of contamination in the pretreatment operation.

FIG. 1 illustrates a schematic flow of an apparatus used in the method of the present invention, and the following description will be made accordingly. In the diagram, valve A is, for example, a 3-way valve, and valves B and C are 6-way switching valves (in the diagram, the 6-way switching valve is a combination of 3 paths 1-2.3-4.5-6, or 2-way switching valves). -3° 4-5. It is possible to simultaneously pass liquid through a combination of the three routes of 6-1.

Operations with this device include regenerating the neutralizing resin, collecting sample solutions,
It can be roughly divided into five categories: neutralization of sample solution, pre-concentration of chloride ions, and separation detection.

First, in the regeneration operation of the neutralization resin, the regeneration acid is pumped into the neutralization column 2 via the A valve and the B valve (maintaining the flow state of 1-2, 3-4, and 5-6) using the pump 1. Send liquid and close C valve (1-2,
Maintain the fluid flow status of 3-4 and 5-6. ) and is discharged to the outside from the discharge port 3.

Next, by operating only valve A, the pump 4 sends deionized water for cleaning through valves A and B to the neutralization column 2 in the same flow as the regenerating acid to remove excess acid. Clean the neutralizing resin except for the "Example for Neutralization".

To collect the sample solution, use a syringe or the like to transfer the sample solution from the sample line (not shown) to valve B (1-2゜3-4.5-
Maintain the fluid flow state of 6. ) A certain amount of sample solution is collected and held by sending it to the sample collection tube 5 through the IN of the B valve, and the excess sample is discharged from the OUT of the B valve to the sample line.

Neutralization of the sample solution and preconcentration of chloride ions are performed with valve A in the state of the neutralizing resin washing operation described above.

Operate the C valves to the flow state of 2-3.4-5.6-1, respectively, and pump deionized water for cleaning to the A valve with pump 4.

The liquid is sent to the sample collection tube 5 through the B valve, and a certain amount of the sample solution is pushed out and introduced into the neutralization column 2 through the B valve to neutralize the sample solution. Next, it is introduced into a pre-concentration column 6 through a C valve to adsorb chloride ions, and excess deionized water for washing is disposed of outside through a discharge port 3 through a C valve.

In the separation and detection operation, the C valve is operated in the flow state of 1-2.3-4.5-6, and the eluent is sent to the preconcentration column 6 via the C valve by the pump 7, and the eluted trace chloride is removed. A solution containing ions is introduced into separation column 8 via C-valve. The chloride ion separated from other anions is detected by the halide ion selective electrode of the detector 9, and the potential change measured by the potential measuring device 10 is converted into a chromatogram by the recorder 1.
Record by 1.

By using six-way switching valves such as B and C valves, this device can regenerate the neutralizing resin in parallel with the separation detection operation, and can also perform operations other than separation detection. Even in this case, since the liquid can be passed through the halide ion selective electrode of the detector 9, the baseline (base potential) can be stabilized.

The cation exchange resin used in the present invention has a gel type or porous type structure based on a copolymer of styrene, methacrylic acid, acrylic acid, etc. and divinylbenzene, and has a sulfonic acid group and a carboxylic acid group. Alternatively, examples include those having an iminodiacetic acid group, an aminophosphoric acid group, etc. as an exchange group. Among these, the strongly acidic sulfonic acid type is more preferable because it can be rapidly regenerated.

The amount of cation exchange resin used depends on the caustic concentration and volume of the sample to be analyzed. For example, the exchange capacity of commercially available cation exchange resins is usually 2 to 4 milliequivalents/7! Since it is about the same as a resin, 1 ml of caustic soda with a concentration of 10 mol/j
When neutralizing, 2.5 to 5 ml of resin is equivalent.

However, if neutralization is incomplete, the hydroxide ions will elute before the chloride ions during the elution operation, and will respond to the halide ion-selective electrode, so the finger will be sensitive to the amount of chloride ions. On the other hand, if a large amount of chloride ions remain, it will affect the measured value of chloride ions. Moreover, if the amount of cation exchange resin is excessive, neutralization will be completed, but the washing time in the pre-concentration operation will take a lot of time, so the speed of analysis will be lost. From this point of view, the amount of cation exchange resin for neutralization is preferably 1.5 to 2 times the theoretically required amount. Although the particle size of the cation exchange resin is approximately 10 to 100 mesh, it is possible to sufficiently achieve the purpose, but a particle size of 20 to 60 mesh is more preferably used.

As the regenerating acid for converting these cation exchange resins into H-type, inorganic acids or organic acids other than those obtained by salting can generally be used. In this case, if the cleaning in the regeneration operation is insufficient, the anion exchange resin will adsorb the remaining anion (conjugate base) of the regeneration acid in the preconcentration operation for the next analysis. Therefore, if this resin adsorbs the anion more strongly than chloride ion, the adsorption of chloride ion will be hindered. Also, since the adsorbed anions are guided to the detection section during the elution operation, they will affect the measured value if they respond to the halide ion selective electrode.

For these reasons, it is preferable to use nitric acid or acetic acid as the regenerating acid.

The anion exchange resin for preconcentration used in the present invention is required to quickly and reliably adsorb trace amounts of chloride ions. The anion exchange resin suitable for the purpose of the present invention has a gel type or porous type structure based on a copolymer of styrene, acrylic acid ester, etc. and divinylbenzene, and has a quaternary ammonium base, primary to Examples include those with triamines or phenolic weak bases as exchange groups,
Preferably, one having a strongly basic quaternary ammonium base having exchange ability in a wide 1)H region is used. It is desirable that the amount of these resins has an exchange capacity that is at least 1000 times greater than the amount of raw chloride ions in the sample to be analyzed by the present invention. For example, the chloride ion concentration is 3.5 μ
When processing 1 ml of caustic alkali that is 'J/rd,
The chloride ion contained in this is 3.5μ3. i.e. 1x
Since the exchange capacity of commercially available anion exchange resins is usually 1 to 2 mm/ffi/mi resin, a resin amount of 0.1 d is sufficient. In addition, it is thought that the smaller the resin particle size, the faster the adsorption reaction will proceed, but on the other hand, the column pressure loss will increase and elution will be difficult.
00 mesh is more preferred.

The anion exchange resin for separation used in the present invention includes the same anion exchange resin for preconcentration as described above. The appropriate amount of resin is 3 to 20 times the amount used for pre-concentration. The appropriate particle size is 60 to 300 mesh, and 100 to 300 mesh.
~250 meshes is more preferred.

Examples of the halide ion selective electrode used in the present invention include a silver electrode, a chloride electrode, a bromide electrode, an iodide electrode, and a silver sulfide electrode.

In the present invention, deionized water is used as washing water in carrying out the analysis. Following the neutralization of the sample solution, wash water is used to introduce trace chloride ions into the preconcentration column.
If the amount of washing water is small, all of the chloride ions cannot be adsorbed to the preconcentration column. Therefore, the amount of washing water used in the present invention needs to be at least twice, preferably at least 5 times, the amount of cation exchange resin for neutralization.

In the present invention, an ion-selective electrode is used as a detector, but since the response of the electrode is usually unstable in dilute solutions with low ionic strength such as deionized water, the response of the electrode is It is common practice to perform measurements by adding a fixed amount of a solution containing ions unrelated to the ion. In the present invention, by using an ion species unrelated to the response of the halide ion selective electrode as an eluent, it simultaneously serves as an ionic strength regulator. Compounds that meet this condition include nitrates and acetates of alkali metals such as potassium and sodium. The concentration of the eluent is the adsorption capacity of the anion exchange resin.

Although it is determined appropriately depending on conditions such as the length of the separation column and the flow rate of the eluent, the concentration is usually 0.1 mol/l! By using the above eluent, it is possible to stabilize the response behavior of the ion-selective electrode.

When eluent is passed through a pre-concentration column, the initial eluate portion that has passed through the column contains residual deionized water, but the separation column separates this initial eluate portion with a dilute salt concentration and chloride ions. Can be separated. Furthermore, even if some hydride ions remain during the neutralization operation, they can be separated from chloride ions using a separation column.
Chloride ions can be determined without any problem.

The materials for each line and valve used in the device used in the present invention include polytetrafluoroethylene and polypropylene, which are chemically stable because acids and concentrated salts are passed through and trace amounts of chloride ions are to be measured. Synthetic resins such as are preferred.

In the pre-concentration operation, chloride ions are adsorbed in a downward flow from the top of the resin, and in the elution operation, conversely, in an upward flow from the bottom, the chloride ions adsorbed on the top of the resin are quickly removed. It can be eluted.

(Effects of the Invention) In the method for measuring trace chloride ions in a high-purity caustic solution, the present invention uses an H-type cation exchange resin-packed column to neutralize a sample solution and then before filling it with an anion exchange resin. The above series of steps involves adsorbing trace amounts of chloride ions on a concentration column, then introducing the eluted chloride ions into a separation column packed with anion exchange resin, and detecting and quantifying chloride ions using a halide ion-selective electrode. By performing this operation within a flow injection analysis system, it is possible to eliminate the problem of chloride ion contamination during sample pretreatment and the problem of chloride ion in the acid used for neutralization, which was a problem with conventional colorimetric methods. The effect of ions has been resolved.

The present invention can accurately quantify trace chloride ion concentrations in caustic alkali with quick and easy operations, and online analysis is also possible. Useful for testing for chloride ions.

EXAMPLES The present invention will be explained in detail below using examples. In this example, a special grade amount of raw sterilizing chemicals was used, and ultrapure water was used as deionized water for concentration adjustment and washing.

Example 1 An analysis of a trace amount of chloride in a 30% by weight caustic soda solution was carried out under the following conditions using an apparatus having the flow shown in FIG. 1.

Cation exchange resin with sulfonic acid group as a functional group (
“Dowex 50W J 100” manufactured by Dow Chemical Company
~200 mesh, exchange capacity 4.5 meq/wet resin) neutralizing column (inner diameter 12 mm x length 50 mm)
In addition, an anion exchange resin having a quaternary ammonium base as a functional group (Dowex 1x8 J
100 to 200 meshes, exchange capacity 1.2 meq/wet resin) to a pre-concentration column (inner diameter 6 mm x length 15 mm)
), add 0.3 ml to a separation column (inner diameter 6 mm x length 100
mm) to 2.5m! Each was filled.

One sample of the sample solution was collected using a sample collection tube made of a Teflon tube with an inner diameter of 2 mm and a length of 33 cm.

A 1.0 mol/j nitric acid solution was used as an acid solution for regenerating the cation exchange resin for neutralization, and a 1.0 mol/g nitrified sodium solution was used for elution. In addition, a chloride ion selective electrode was used as the halide selective electrode of the detector.

First, a nitric acid solution was passed through the neutralization column for 5 minutes at a flow rate of 1 ml/min, and then deionized water for washing was passed at a flow rate of 5 d/min for 5 minutes, and the pH of the effluent from the outlet 3 was was confirmed to be neutral.

Next, a 30% by weight caustic soda solution containing a trace amount of chloride ions was collected in a sample collection tube, and extruded using deionized water for washing at a flow rate of 1 force/min for the first 3 minutes to perform a neutralization reaction. Subsequently, washing and adsorption of chloride ions onto the preconcentration column were performed for 5 minutes at a flow rate of 3 ml/min.

Finally, the eluate was passed through a preconcentration column and a separation column at a flow rate of 1 m/min to detect and quantify chloride ions.

The solution for the calibration curve is 0.0% from the 100100O chloride ion standard solution. 1. 2. Chloride ion solutions of 3 mg/Q were each prepared using deionized water and analyzed in the same manner as for the sample solution, except that the neutralizing resin was not regenerated.

From the chromatogram obtained by the above procedure, a calibration curve shown in Figure 2 is created, and the specific gravity (
The chloride concentration in the sample solution (N
The 10 measurement values obtained (as aCU) are O, d3.0
147.0.50.0.45.0.44.0.52゜0
．． 45.0.46.0.43. and 0.45 ppm. The average value of these was 0.460 ppm, and the coefficient of variation was 6.1%, so results with good reproducibility were obtained.

Next, 95 volumes of the sample solution were collected into four polyethylene volumetric flasks, and 1 mCl/1 mCl/11 chloride ion standard solution was added to each of the 4 polyethylene volumetric flasks. 1. 2. 3 d was added and deionized water was added to make a total of 100 d. These solutions were analyzed in the same manner as for the sample solution, and the standard addition line shown in Figure 2 was obtained. The chloride concentration in the sample solution (as NaCl) was determined to be 0.50 ppm by applying the standard addition method to these measured values. It can be seen that there is good agreement with the measured values obtained by the method described above.

Example 2 The trace chloride concentration in a 48% by weight caustic potassium solution was measured under the same column conditions as in Example 1.

The amount of sample to be collected is 2ml1, so the inner diameter is 3mm,
.

A sample collection tube was constructed using a Teflon tube with a length of 29 cm.

95 d of sample solution was taken into four polyethylene volumetric flasks, 0.1, 2. 3 d of 1 m(]/N chloride ion standard solution were added to each flask, and deionized water was added for a total of 100 mI!). These solutions were analyzed in the same manner as in Example 1, and the standard addition line shown in FIG. 3 was obtained.

Based on these measured values, the chloride concentration (as Kα) in the sample solution was determined by applying the standard addition method and was found to be 1.36 pp.
It was m.

Comparative Example Each sample solution measured in Examples 1 and 2 was neutralized using reagent-grade nitrification, and then the standard addition method was performed using a conventional colorimetric method using mercuric thiocyanate. The chloride concentration in the sample solution was 0.81 pf)m (as NaCf7) for the sample of Example 1.
, the sample of Example 2 was 1.64 ppm (KCf!)
Met. It can be seen that this is considerably excessive compared to the results of the previous example.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic flow of an apparatus used in an embodiment of the method of the present invention. Figures a and b in Fig. 2 are diagrams showing a, a calibration curve, and a standard addition curve obtained in Example 1. FIG. 3 is a diagram showing the standard addition line obtained in Example 2.

Claims (1)

[Claims] In the method for measuring trace amounts of chloride ions in high-purity caustic alkaline solutions, the sample solution is passed through an H-type cation exchange resin-filled column for neutralization, and then passed through an anion-exchange resin-filled preconcentration column. After adsorbing chloride ions, the solution containing chloride ions eluted with an eluent is passed through a separation column packed with anion exchange resin, and the separated chloride ions are detected and quantified using a halide ion-selective electrode. A flow analysis method characterized in that the series of operations described above are performed within a flow injection analysis system.