JP2012008070A - SEPARATION METHOD OF CHLORIDE ION CONTAINING 36Cl AND MANUFACTURING METHOD OF SAMPLE FOR ACCELERATOR MASS SPECTROMETRY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separation method for accurately separating chloride ion containingCl from chloride ion containingS in a shorter time than that required for a conventional barium sulfate method; with high reproducibility not depending on the subjectivity, ability, or skill of an operator; even in a case that a chloride ion concentration of a sample to be tested is low.SOLUTION: Chloride ion containingCl in a sample to be tested is separated from chloride ion containingS by allowing a sample to be tested to be subjected to column chromatography using a strong basic anion exchange resin in which counter ion thereof is composed of an anion other than chloride ion as a filler.

Description

The present invention relates to a method for separating ³⁶ Cl-containing chloride ions and a method for preparing a sample for accelerator mass spectrometry using the same. In more detail, the present invention is, when analyzed by the residence time of the groundwater accelerator mass spectrometry ^{36 Cl} is one of the important radioisotope in evaluating (groundwater age) (Accelerator Mass Spectrometry), ³⁶ Separation method of ³⁶ Cl-containing chloride ions suitable for pretreatment to remove ³⁶ S that becomes a measurement interference component of Cl, and further a sample for accelerator mass spectrometry from which ³⁶ S that becomes a measurement interference component of ³⁶ Cl is removed It relates to a manufacturing method.

  In the safety assessment of radioactive waste disposal and environmental issues, clarifying the flow of groundwater is important in clarifying the migration of radioactive materials and heavy metals. However, since the flow of groundwater is extremely slow, it is extremely difficult to measure this directly. Therefore, a method for evaluating the flow of groundwater by measuring the isotope ratio of ions dissolved in the groundwater and evaluating the residence time (groundwater age) of the groundwater has been proposed (Non-Patent Documents 1 to 3). ).

Here, ³⁶ Cl, which is a radioisotope of chloride ion, is that the chloride ion exists in groundwater relatively stably, and the half-life of ³⁶ Cl is as long as 300,000 years, and the groundwater age is about 1.8 million years. Therefore, it is reported that it is one of radioisotopes that are extremely important in evaluating the age of groundwater (Non-Patent Documents 4 to 6).

For analysis of ³⁶ Cl dissolved in groundwater, accelerator mass spectrometry (hereinafter, also referred to as AMS) is usually used (Non-patent Document 7). AMS is an analysis method that utilizes the fact that the radius of the charged particles in a magnetic field depends on the mass number, and the proportion of ³⁶ Cl in the total chloride ions dissolved in groundwater ( ³⁶ Cl / Cl). ^Can be quantified to a small value of the order of 1 × 10 ⁻¹⁵ .

Thus, AMS is an analytical method having excellent quantitativeness, but it also has certain drawbacks. That is, since this analysis method uses an element mass difference, the presence of isobaric bodies having the same or very close mass number can affect the analysis value. ^In the analysis of ³⁶ Cl / Cl, ³⁶ S, which is a radioactive isotope of sulfur, can affect the analysis value.

Therefore, in the analysis of ³⁶ Cl / Cl using AMS, conventionally, the analysis accuracy was improved by separating ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions in advance by chemical treatment ( Non-Patent Documents 7 to 10, and in the following description, this conventional method is referred to as a barium sulfate method).

The barium sulfate method utilizes the difference in solubility between barium sulfate and barium chloride. The specific procedure will be roughly described with reference to FIG. First, silver nitrate is added to a test sample (for example, an AMS measurement sample such as groundwater) to generate a precipitate (S101), and this precipitate is collected (S102). Next, ammonia water is added to the precipitate to dissolve the precipitate (S103), and barium sulfate is added to the precipitate to generate a barium sulfate precipitate (S104). And barium sulfate precipitation is removed and supernatant liquid is collect | recovered (S105), and also the sulfate ion concentration reduction process of this supernatant liquid is performed (S106). Conventionally, the supernatant obtained by the above-described series of steps is used as a solution from which ³⁶ S-containing sulfate ions have been removed, and nitric acid and silver nitrate are added to this solution to form a silver chloride precipitate (S107). Was collected (S108), and this was subjected to accelerator mass spectrometry as a sample for analysis.

  The series of steps will be described in more detail.

  In the precipitation generating step (S101) by adding silver nitrate to the test sample, nitric acid is added to the collected test sample such as ground water to adjust the pH to 2.0 or less, and then an aqueous silver nitrate solution is added thereto to generate a precipitate. Let In this step, an excessive amount of silver nitrate is added to the dissolved chloride ions in order to minimize the loss of chloride ions. Therefore, the precipitation includes not only silver chloride precipitation but also silver sulfate precipitation. Further, this step is performed under light shielding to prevent the formation of silver oxide. The test sample to which silver nitrate has been added is allowed to stand for about 48 hours in the dark to allow the precipitate to grow and become large so that the precipitate can be easily recovered by solid-liquid separation.

  In the precipitation recovery step (S102), the precipitate obtained in the precipitation generation step (S101) by adding silver nitrate is transferred to a centrifuge tube, centrifuged, and the supernatant is removed (solid-liquid separation). Rinse and apply to the next step. Rinsing is performed by adding ultrapure water to the collected precipitate and shaking it, and centrifuging to remove the supernatant (solid-liquid separation) and collect the precipitate. After rinsing, the collected precipitate is used for the next step without drying.

  In the precipitation dissolution step (S103) by adding aqueous ammonia, aqueous ammonia is added to the undried precipitate recovered in the precipitation recovery step (S102) to dissolve the precipitate. This step utilizes the fact that silver ions are complexed with thiosulfate ions, cyanide ions, and ammonium ions, and therefore dissolve when ammonia is added to the silver chloride / silver sulfate precipitates. The precipitation solution containing the dissolved precipitate is appropriately diluted with pure water.

  In the barium sulfate precipitation generation step (S104) by addition of barium nitrate, the barium nitrate solution is added to the precipitation solution obtained in the precipitation dissolution step (S103) by addition of aqueous ammonia to generate a barium sulfate precipitation. This process utilizes the fact that the solubility of barium sulfate (0.22mg / 100mL) is lower than that of barium chloride (1.7g / 100mL), so sulfate ions are preferentially precipitated as barium sulfate. It is. In order to make the precipitate grow large so that the precipitate can be easily recovered by solid-liquid separation, the precipitate solution added with the barium nitrate solution is allowed to stand for 2 to 7 days with occasional shaking.

  In the step of removing the barium sulfate precipitate and collecting the supernatant (S105), the solution containing the barium sulfate precipitate obtained in the barium sulfate precipitation generation step (S104) by adding barium nitrate is centrifuged to remove the barium sulfate precipitate. Remove and collect supernatant.

  In the step of reducing the sulfate ion concentration in the supernatant (S106), the steps S104 to S105 are repeated for the supernatant to remove as much sulfate ions as possible in the supernatant. That is, the barium nitrate solution is again added to the supernatant, and the operator visually confirms whether or not barium sulfate white precipitates are formed. If barium sulfate precipitates are generated, the series of steps S104 to S105 follows. Remove the barium sulfate precipitate and collect the supernatant. This operation is repeated until no production of barium sulfate from the supernatant occurs.

Through the above steps (S101~S106), ³⁶ S-containing sulfate ions from the test sample is removed.

  Then, nitric acid and silver nitrate are added to the supernatant liquid which has been confirmed to be free from the production of barium sulfate to produce a silver chloride precipitate (S107). Heat with a hot plate until the supernatant is clear.

  In the silver chloride precipitation recovery step (S108), the liquid phase is collected and removed from the solution containing the silver chloride precipitate obtained in the step (S107) of generating the silver chloride precipitate, thereby recovering the silver chloride precipitate. Is rinsed (washed) with ultrapure water and dried at 60 ° C to 70 ° C.

  Through the above steps (S107 to S108), a sample for accelerator mass spectrometry is obtained.

Teruaki Iwatsuki, Xu-Katsu, Shigeru Ito, Masato Abe, Masato Watanabe, “Estimation of groundwater flow using 14C isotopes”, cycle mechanism technique, (1999) No.4 93-100 Kotaro Nakata, Takuma Hasegawa, Yuichi Tomioka, “Examination of the relationship between 87Sr / 86Sr and dissolved water age in dissolved Sr ions”, Proceedings of Autumn Lecture Meeting of the Groundwater Society of Japan, 42 Eggenkamp M., and Coleman L., The effect of aqueous diffusion on the fractionation of chlorine and bromine stable isotopes, Geochimica et Cosmochimica Acta 73 (2009) 3539-3548. Cresswell R., Bauld J., Jacobson G., Khadka M., Jha M., Shrestha M., and Regmi M., A first estimate of ground water ages for the deep aquifer of the Kathmandu Basin, Nepal, using the radioisotope chlorine-36, Ground Water, 39, (2001) 449-457. Davis S., Cecil L., Zreda M., and Moysey S., Chlorine-36, bromide, and the origin of spring water, Chem. Geol., 179, (2001) 3-16. Bentley H., Phillips F., Davis S., Harbermehl M., Airey P., Calf G., Elmore D., Gove H., and Torgersen T., Chlorine 36 dating of very old groundwater 1. The Great Artesian Basin , Australia, Water Resources Research, 22, (1986) 1991-2000. Elmore D., Fulton B., Clover M., Marsden J., Gove H., Naylor H., Purser K., Kilius L., Beukens R., and Litherland A., Analysis of 36Cl in environmental water samples using an electrostatic accelerator, Nature, 277 (1979) 22-25. Torgersen T., Habermehl M., Phillips F., Elmore D., Kubik P., Jones B., Hemmick T., and Gove H., Chlorine 36 dating of very old groundwater 3. Further studies in the Great Artesian Basin, Australia, Water Resources Research, 27 (1991) 3201-3213. Nagashima Y., Seki R., Takahashi T., and Arai D., Status of the 36Cl AMS system at the University of Tsukuba, Nucl. Instr. And Meth. B, (2000) 129-133. Phillips F. (2000): Chloribe-36. In Environmental tracers in subsurface hydrology. Chapter-10 P299-348. Kluwer Academic Publishers.

  However, the barium sulfate method has a number of problems.

  The first problem is that many processes that require a long period of time for processing are included, so that it takes at least a long period of 1 to several weeks until all processes are completed. Specifically, in step 101, a period of about 2 days is required for growing silver chloride and silver sulfate precipitates, and in step S104, a period of 2-7 days is required for growing barium sulfate precipitates. In addition, in step S106, in order to reduce the sulfuric acid concentration of the supernatant as much as possible, a considerable period may be required by repeating step S104 several times. By including these steps, there is a problem that it takes a long period of time of at least one to several weeks until all the steps are completed.

As a second problem, in step S106, since the sulfate ion concentration of the supernatant cannot be lowered below the solubility product of barium sulfate, the final amount of ³⁶ S-containing sulfuric acid corresponding to the solubility of barium sulfate is obtained. It is mentioned that ions can remain.

  The third problem is that it is difficult to expect reproducibility due to the operations that can be perceived by the worker and operations that depend on the skill and skill level of the worker. Specifically, in step S106, the presence or absence of the formation of barium sulfate precipitates is confirmed by visual confirmation that the subjectivity of the operator can enter, so there is a problem that reproducibility is difficult to expect. Further, in steps S105 and S106, there may be a barium sulfate suspended matter in the supernatant, so that the operator is required to have a skill to collect the supernatant without sucking it up. Therefore, there is a problem that the reproducibility is likely to depend on the skill and skill level of the operator.

As a fourth problem, when a barium sulfate colloid is produced in steps S104 and S106, it takes time to remove the colloid. ^This is because it is difficult to separate the ³⁶ Cl-containing chloride ion and the ³⁶ S-containing barium sulfate colloid, and as a result, it is difficult to separate the chloride ion and the sulfate ion.

  As a fifth problem, when a dilute solution having a chloride ion concentration of 1 ppm or less is used as a test sample, it is difficult to form a silver chloride precipitate even when a silver nitrate solution is added. In some cases, the conventional method cannot be applied.

From the above, it has been desired to establish a new method for separating ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions, which can solve the above problems. In addition, it has been desired to establish a new method for preparing a sample for accelerator mass spectrometry from which ³⁶ S that is a measurement interference component of ³⁶ Cl is removed.

The present invention has been made in view of such a demand, and has a shorter time than the barium sulfate method, high reproducibility without depending on the subjectivity, skill, and skill level of the operator, and the chloride of the test sample. It is an object of the present invention to provide a method capable of reliably and accurately separating ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions even when the ion concentration is dilute.

Further, the present invention is a case where the quality is equal to that in a shorter time than the barium sulfate method, without depending on the subjectivity, skill, and skill level of the worker, and the chloride ion concentration of the test sample is low. Another object of the present invention is to provide a method for producing a sample for accelerator mass spectrometry in which ³⁶ Cl-containing chloride ions are reliably and accurately separated from ³⁶ S-containing sulfate ions.

In order to solve such a problem, the inventor of the present application has intensively studied to separate ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions by a completely different technique. As a result, it is possible to separate ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions by performing column chromatography on a test sample using a strongly basic anion exchange resin with nitrate as the counter ion as a filler. I found out.

Based on this finding, the inventor of the present application conducts column chromatography on a test sample using a strongly basic anion exchange resin whose counterion is an anion other than chloride ion as a filler, and contains ³⁶ Cl. It led to the finding that the possibility of separating the chloride ions from the ^{36 S-containing} sulfate ions is introduced, and have completed the present invention further extensive studies.

That is, the ³⁶ Cl-containing chloride ion separation method of the present invention performs column chromatography on a test sample using a strongly basic anion exchange resin whose counter ion is an anion other than chloride ion as a packing material. Thus, the ³⁶ Cl-containing chloride ions in the test sample are separated from the ³⁶ S-containing sulfate ions.

Here, in the method for separating ³⁶ Cl-containing chloride ions of the present invention, a nitric acid solution is used as an eluent, and the concentration of the nitric acid solution is 500 to 2500 ppm in the liquid phase contacting the packing material in column chromatography. It is preferable that the concentration be maintained. In this case, when the eluent is a nitric acid solution, the counter ion of the strongly basic anion exchange resin is preferably a nitrate ion.

In addition, in the method for preparing a sample for accelerator mass spectrometry of the present invention, ³⁶ Cl-containing chloride ions separated from ³⁶ S-containing sulfate ions by the separation method of the present invention are reacted with silver ions to produce ³⁶ Cl-containing silver chloride. I try to let them.

According to ^{36 Cl-containing} method of separating chloride ions present invention, in a shorter time than the barium sulfate method, which is a conventional method, it can be reliably and accurately separate the ^{36 Cl-containing} chloride ions from ^{36 S-containing} sulfate ions It becomes possible. In addition, since ³⁶ Cl-containing chloride ions can be separated from ³⁶ S-containing sulfate ions only by column chromatography operation, it does not depend on the subjectivity, skill, and skill level of the worker as in the past, and it is complicated. It is possible to easily separate the ³⁶ Cl-containing chloride ion from the ³⁶ S-containing sulfate ion with high reproducibility without going through a process requiring operation. Further, even when the chloride ion concentration of the test sample is dilute, the ³⁶ Cl-containing chloride ions can be separated from the ³⁶ S-containing sulfate ions.

According to the method for preparing a sample for accelerator mass spectrometry of the present invention, accelerator mass in which ³⁶ Cl-containing chloride ions are reliably and accurately separated from ³⁶ S-containing sulfate ions in a shorter time than the conventional method of barium sulfate. It is possible to prepare a sample for analysis. In addition, since ³⁶ Cl-containing chloride ions are separated from ³⁶ S-containing sulfate ions only by column chromatography operation, it does not depend on the subjectivity, skill, and skill level of workers as in the past, and it is complicated. It is possible to easily produce a sample for analysis of equal quality without going through a process that requires. In addition, even when the chloride ion concentration of the test sample is dilute, it is possible to prepare a sample for accelerator mass spectrometry in which ³⁶ Cl-containing chloride ions are reliably and accurately separated from ³⁶ S-containing sulfate ions. It becomes.

It is a process flow figure of the separation method of the present invention, and the preparation method of the sample for accelerator mass spectrometry. It is a figure which shows the result of having plotted the density | concentration of the chloride ion and the density | concentration of a sulfate ion which were not adsorb | sucking to a filler after a batch test with respect to the nitrate ion density | concentration of a liquid phase. It is a conceptual diagram of the column chromatography apparatus used in the Example. It is a figure which shows the relationship (chromatogram) of the dripping amount of the eluent with respect to a chloride ion concentration and a sulfate ion concentration. It is a figure which shows the relationship (chromatogram) of the dripping amount of an eluent with respect to a chloride ion concentration when the quantity of a test sample is 1 mL, 10 mL, and 100 mL. It is a figure which shows the peak shape of a chloride ion when a 100 mL test sample is processed by column chromatography, and a sulfate ion. It is an enlarged view of the enclosure part of FIG. The peak shape of chloride ion and sulfate ion is shown when the test sample is processed by column chromatography with the packing height of the filler fixed at 15 cm and the nitric acid concentration of the nitric acid solution changed to 2000 ppm, 1500 ppm and 1000 ppm. FIG. It is a figure which shows the peak shape of a chloride ion when a test sample is processed as a dilute solution by column chromatography. It is a process flow figure of the preparation methods of the sample for accelerator mass spectrometry by the barium sulfate method which is the conventional method.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

The ³⁶ Cl-containing chloride ion separation method of the present invention is performed by performing chromatography on a test sample using a strongly basic anion exchange resin whose counter ion is an anion other than chloride ion as a filler, The ³⁶ Cl-containing chloride ions in the test sample are separated from the ³⁶ S-containing sulfate ions. The separated ³⁶ Cl-containing chloride ions are reacted with silver ions to produce ³⁶ Cl-containing silver chloride, which is used for AMS analysis.

  In column chromatography, when a solution is passed through a column (acrylic or glass tube) packed with a packing material, the solute is removed from the column due to the strength of the affinity between the packing material and the solute and the size of the solute. This is a technique for separating solutes by using different discharge speeds. Column chromatography has the advantage that it is not easily affected by coexisting ions, and that it can be concentrated simultaneously in the process of separating and recovering the object contained in the test sample.

Hereinafter, based on the process flow diagram of FIG. 1, a manufacturing method of a ³⁶ method of separating ^Cl containing chloride ions and AMS analytical sample of the present invention will be described in detail.

The process flow shown in FIG. 1 generally includes a process for separating ³⁶ Cl-containing chloride ions in steps S1 to S3 and a process for preparing a sample for AMS analysis in steps S4 to S5.

<Process S1>
In step S1, as a preparation for performing column chromatography, the column is filled with a packing material.

As the filler, various type I or type 2 strongly basic anion exchange resins can be used, and type I strongly basic anion exchange resins can be suitably used. However, some strongly basic anion exchange resins have a so-called Cl form in which the counterion at the exchange site is a chloride ion. If the counter ion is a chloride ion, the total chloride ion concentration in the test sample varies depending on the chloride ion of the counter ion, and there is an error in the quantitative analysis value of ³⁶ Cl contained in the total chloride ion. Occurs. Therefore, when the counter ion of the strongly basic anion exchange resin is a chloride ion, the chloride ion is replaced with an anion other than the chloride ion and then subjected to column chromatography. For example, when Dowex (Dowex, manufactured by Dow Chemical Co.), which is a type I strongly basic anion exchange resin, is used as the strong base anion exchange resin, the counter ion at the time of sale of the exchange resin is chloride ion. For this reason, a substance in which this is replaced with an anion other than chloride ion is used.

  Here, it is preferable to match the counter ion of the strongly basic anion exchange resin with the anion that is the main component of the eluent dropped into the column in step S3. In this case, it is possible to prevent a change in the volume of the packing material due to the dropping of the eluent and prevent the column from being damaged or the separation performance from being lowered.

In order to make the anion of the strongly basic anion exchange resin coincide with the anion contained in the eluent, the anion concentration in the eluent is set to a high concentration (for example, about 2 mol / L), and the resin-filled partial volume of 20 Add more than double the solution to the resin packed in the column. Moreover, you may make it incorporate the washing | cleaning process by a neutral salt etc. as needed. As a specific example, a method for substituting an opposite ion of a strongly basic anion exchange resin from a salt ion to a nitrate ion will be described. First, a wet resin is packed into a column, and a high-concentration nitric acid solution (for example, 2.0 mol / L) is dropped into the column and brought into contact with the filler. Next, sodium nitrate (for example, 1.0 mol / L), which is a neutral salt, is dropped into the column and brought into contact with the packing material. Then, a highly concentrated nitric acid solution (for example, 2.0 mol / L) is again dropped into the column and brought into contact with the packing material. After performing these series of treatments, the resin is taken out from the column, put in a high concentration nitric acid solution (for example, 2.0 mol / L), and immersed for example overnight. At this time, it is preferable to exchange the high-concentration nitric acid solution one or more times (for example, twice). Finally, by washing with pure water, the counter ions of the strongly basic anion exchange resin can be replaced with nitrate ions from the salt ions. In this way, after the separation treatment of the present invention is performed by a method in which a high-concentration anion solution is brought into contact with a filler to make the counterion of the strongly basic anion exchange resin coincide with the anion of the eluent. The ³⁶ S-containing sulfate ions adsorbed on the filler can be desorbed from the filler and replaced with the anion of the eluent again, and the filler can be reused.

The inner diameter of the column, the packing height of the packing material, and the particle size (packing density) of the packing material take into account the time required for separation by column chromatography and the separability of ³⁶ Cl-containing chloride ions and ³⁶ S-containing sulfate ions. Can be determined. That is, the smaller the inner diameter of the column, the higher the packing height, and the smaller the particle size of the packing material, the higher the separability, but the longer the separation takes. Conversely, the larger the inner diameter of the column, the lower the packing height, and the larger the particle size of the packing material, the shorter the separation, but the lower the separation. In addition, if the inner diameter of the column is too large, it becomes difficult to bring the test sample or the eluent into contact with the entire packing material. Therefore, taking these into account, the inner diameter of the column, the packing height of the packing material, and the particle size (packing density) of the packing material can be appropriately determined. As an example, the inner diameter of the column is about 1 cm, the packing height is 10 to 15 cm, and the particle size of the packing is 200 to 400 mesh, so that the test sample such as 1 mL to 10000 mL of ground water contains ³⁶ Cl. It is possible to separate chloride ions from ³⁶ S-containing sulfate ions.

  As a filler having a particle size of 200 to 400 mesh, for example, Dowex 1x8 200-400 (manufactured by Dow Chemical Co., Ltd.) can be used. However, the present invention is not limited to this, and packing of the filler into the column is possible. In consideration of the density, strong basic anion exchange resins having various particle sizes, or strongly basic anion exchange resins adjusted to various particle sizes by pulverization or the like can be used.

<Process S2>
In step S2, the test sample is dropped into the column prepared in step S1. As a result, the test sample comes into contact with the filler, and ³⁶ Cl-containing chloride ions and ³⁶ S-containing sulfate ions contained in the test sample are adsorbed by the filler. When the test sample is dropped into the column, the test sample splashes on the inner wall of the column, or the test sample adheres to a flow path (pipe, tube, etc.) that leads the test sample to the column. Therefore, it is preferable that the flow path after the sample introduction is appropriately washed with pure water or the like, and the washed pure water is guided into the column. Thereby, the loss of ³⁶ Cl containing chloride ions contained in the test sample can be minimized.

Examples of test samples include, but are not limited to, various environmental samples such as groundwater that are required to separate ³⁶ Cl-containing chloride ions from ³⁶ S-containing sulfate ions for use in AMS analysis. It is not a thing.

<Process S3>
In step S3, an eluent is added dropwise to the filler, and ³⁶ Cl-containing chloride ions are removed from the filler by using the difference in adsorption force between the ³⁶ Cl-containing chloride ions and the ³⁶ S-containing sulfate ions on the filler. And is separated from the ³⁶ S-containing sulfate ion.

The eluent is not limited to a specific one because it can be separated even with an ion having a weak adsorptive power, but it has a weaker adsorptivity to a strongly basic anion exchange resin than a sulfate ion. A solution mainly composed of anions stronger than ions can be expected to be advantageous for separation (good separation performance and high efficiency). For example, iodide ions (I ⁻ ), nitrate ions (NO ₃ ⁻ ), A solution mainly containing chromate ions (CrO ₄ ²⁻ ) and bromide ions (Br ⁻ ), and particularly a solution mainly containing nitrate ions (nitric acid solution) is preferably used. In this case, ³⁶ Cl-containing chloride ions and ³⁶ S-containing sulfate ions can be separated with high separability. Further, since silver nitrate produced together with silver chloride is soluble in water when the sample for AMS analysis is brought into contact with silver ions, the nitrate ions are not mixed into the silver chloride precipitate. In contrast, iodide ions, chromate ions, and bromide ions react with silver ions to form silver iodide precipitates, silver chromate precipitates, and silver bromide precipitates that have low solubility, and can be mixed with silver chloride precipitates. . Therefore, by using a nitric acid solution as an eluent, high-purity silver chloride can be provided as an analytical sample. In this respect, it can be said that it is preferable to use a nitric acid solution as an eluent.

When the eluent is a nitric acid solution, the concentration of the nitric acid solution is preferably set to a concentration at which the concentration of nitrate ions in the liquid phase in contact with the filler in column chromatography can be maintained at 500 to 2500 ppm. If the nitrate ion concentration is lower than 500 ppm, it is highly possible that the ³⁶ Cl-containing salt ions and the ³⁶ S-containing sulfate ions are not detached from the filler and cannot be separated. Further, when the nitrate ion concentration is higher than 2500 ppm, the desorption of ³⁶ Cl-containing salt ions and the desorption of ³⁶ S-containing sulfate ions occur almost simultaneously, and there is a high possibility that separation is impossible. Although the separation of ³⁶ Cl-containing salt ions and ³⁶ S-containing sulfate ions is ensured by maintaining the concentration of nitrate ions in the liquid phase at 500-2500 ppm, it is more preferably 700-2000 ppm. It is more preferably 2000 ppm, still more preferably 1000 to 1500 ppm, and most preferably 1250 ppm. In this case, while obtaining more reliable separability, the amount of the eluent used can be reduced to reduce the amount of waste liquid finally generated, and the processing time can be shortened.

  The “liquid phase” in contact with the packing material is a liquid component that can exist in the column while the eluent is dripped into the column, that is, a mixed solution of the test sample and the eluent, or a pure liquid. When water is used, it means a mixed solution of the test sample, eluent and pure water.

Also, when using a solution other than the nitric acid solution as the eluent, as in the case of using the nitric acid solution, if the concentration is too low, the ³⁶ Cl-containing salt ions and the ³⁶ S-containing sulfate ions are not detached from the filler and cannot be separated. . On the other hand, if the concentration is too high, desorption of ³⁶ Cl-containing salt ions and desorption of ³⁶ S-containing sulfate ions occur almost simultaneously, and separation is impossible. Therefore, the concentration of the eluent may be determined in consideration of these points.

After a while after the eluent is dropped into the column, ³⁶ Cl-containing chloride ions are contained in the liquid phase flowing down from the bottom of the column. While the liquid phase contains ³⁶ Cl-containing chloride ions, this liquid phase does not contain ³⁶ S-containing sulfate ions. By recovering this liquid phase, the ³⁶ S-containing sulfate ions are separated. ³⁶ Cl-containing chloride ions can be recovered.

For example, the test sample is groundwater, the inner diameter of the column is about 1 cm, the packing height is 15 cm, the particle size of the filler is 200 to 400 mesh, and the eluent is a 2000 ppm nitric acid solution. can eluent dropping amount is recovered ³⁶ Cl-containing chloride ions in the range of 150～350ML. In this ^condition, the ³⁶ S-containing sulfate ions only flow out in a range amount eluent dripping is over 500 mL, since the ³⁶ S-containing sulfate ions in the range of 150~350mL does not flow ^out, the ³⁶ S-containing sulfate ions The separated ³⁶ Cl-containing chloride ions can be recovered. Further, since this operation is completed in about 6 hours, the time required for the treatment can be greatly shortened as compared with the conventional method of barium sulfate. Moreover, it is possible to collect ³⁶ Cl-containing chloride ions from which ³⁶ S-containing sulfate ions have been separated by simple treatment without requiring visual confirmation of the worker or depending on the skill and skill level of the worker, Reproducibility can also be improved as compared with the conventional method of barium sulfate. For example, by using a fraction collector or the like, it is possible to easily recover the liquid phase flowing down from the lower part of the column within a desired amount of elution droplets.

<Step S4>
A sample for use in AMS analysis is prepared from the ³⁶ Cl-containing chloride ions obtained by the above steps (S1 to S3). Specifically, the ^{36 Cl-containing} chloride ions to produce a ^{36 Cl-containing} silver chloride precipitate is reacted with silver ions.

^The method of reacting ³⁶ Cl-containing chloride ions with silver ions is not particularly limited, but the reaction may be performed so as to obtain high-purity ³⁶ Cl-containing silver chloride containing no anions other than chloride ions. This is suitable for improving the accuracy of AMS analysis.

For example, a nitric acid solution is added to a solution containing ³⁶ Cl-containing chloride ions to adjust the pH to 2 or less, and an excessive amount of silver nitrate is added thereto, thereby minimizing the loss of chloride ions and increasing the pH. purity can be obtained in ³⁶ Cl-containing silver chloride. As described above, by using a nitric acid solution as an eluent, the solution containing ³⁶ Cl-containing chloride ions recovered in step S3 contains only nitrate ions as an eluent component. Even if it reacts, it becomes water and soluble silver nitrate, and the ³⁶ Cl-containing silver chloride is substantially free of nitrate ions.

<Step S5>
In step S5, the ^{36 Cl-containing} silver chloride precipitate obtained in step S4 is recovered, which is washed, dried and samples for AMS analysis. Specifically, for example, a sample for AMS analysis can be prepared by rinsing the recovered ³⁶ Cl-containing silver chloride precipitate with pure water or the like and drying at about 60 to 70 ° C.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, silver ions are reacted with ³⁶ Cl-containing chloride ions obtained by the separation method of the present invention to form a ³⁶ Cl-containing silver chloride precipitate. When a sample for use is required, a metal ion other than silver ions may be reacted with ³⁶ Cl-containing chloride ions obtained by the separation method of the present invention to form a precipitate.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
Separation of chloride ion and sulfate ion by column chromatography was examined by batch test.

(1) Test sample Sodium chloride and sodium sulfate were dissolved in water to prepare a simulated treatment solution having a chloride ion concentration and a sulfate ion concentration of 100 ppm, respectively, and this was used as a test sample. In the deep groundwater, the chloride ion concentration is mostly higher than the sulfate ion concentration (Japanese Groundwater Society (ed.), Groundwater quality basics-from famous water to groundwater contamination, 2000, published by Riko Books) . Therefore, the simulated treatment solution used in this example has conditions that make it more difficult to separate chloride ions and sulfate ions than actual groundwater, and it is possible to separate chloride ions and sulfate ions in this simulated treatment solution. If so, the separation technique is applicable to most groundwater.

(2) Eluent A nitric acid solution was used.

(3) Filler Ion-type strongly basic anion exchange resin, Dowex 1x8 (Dow Chemical Co., particle size 200-400 mesh, Cl form) exchange ion counter ion (chloride ion) Was used as a filler.

  Specifically, a filler was prepared according to the following procedure. First, 50 cc of resin (wet state) is filled in an acrylic column tube having an inner diameter of 1 cm, and 1000 mL of a 2.0 mol / L nitric acid solution is dropped at a flow rate of 2.5 mL / min, and then 500 cc of 1.0 mol / L sodium nitrate is added. The solution was added dropwise at a flow rate of 2.5 mL / min. Then, 1000 mL of a 2.0 mol / L nitric acid solution was dropped again at a flow rate of 2.5 mL / min. After these series of treatments, the resin was taken out from the column, and 200 cc of a 2.0 mol / L nitric acid solution was added to 50 cc of the resin and immersed overnight. Thereafter, the operation of replacing the supernatant with a new nitric acid solution was repeated twice. Next, 200 cc of pure water was added to 50 cc of resin, shaken well, waited for 5 minutes until the resin precipitated, and the operation of exchanging the supernatant was repeated 10 times to obtain a filler.

  After this filler was immersed in a nitric acid solution for a long time, the nitric acid solution was subjected to inductively coupled plasma mass spectrometry (manufactured by Agilent Technology, 7500ce, hereinafter referred to as ICP-MS). Was not. From this result, it was confirmed that the counter ion of the resin was substituted from the chloride ion to the nitrate ion by the above treatment.

(4) Batch test method 0.25 g of a filler and 10 mL of a test sample were added to a centrifuge tube made of polypropylene, and a nitric acid solution was further added. The nitric acid solution was added so that the nitrate ion concentration in the liquid phase in the centrifuge tube composed of the test sample and the nitric acid solution was 500 to 20000 ppm (8 to 320 mmol / L).

  Here, as a result of conducting a test in advance to clarify the temporal change in the concentration of chloride ions and sulfate ions in the liquid phase in contact with the filler, the ion exchange between the filler and the liquid phase takes about 1 hour. It was confirmed that a sufficient equilibrium was reached. Therefore, in this example, the centrifuge tube was gently rotated with a tube rotator for 24 hours to ensure that ion exchange reached equilibrium.

  Next, the filler and the liquid phase were separated by a 0.45 μm cellulose mixed ester filter (ADVANTEC, DISMIC25AS045AS), and the liquid was separated by inductively coupled plasma mass spectrometry (manufactured by Agilent Technology, 7500ce, hereinafter referred to as ICP-MS). The chloride ion concentration and sulfate ion concentration of the phase (actually measured is the concentration of sulfur atoms decomposed by plasma).

  FIG. 2 shows the results of plotting the chloride ion concentration and the sulfate ion concentration remaining in the liquid phase without being adsorbed by the filler after the batch test against the nitrate ion concentration in the liquid phase. From the results shown in FIG. 2, it was revealed that chloride ions and sulfate ions can be separated by column chromatography. Moreover, in the adsorption to the filler, sulfate ions are preferentially adsorbed over chloride ions, and the selectivity between chloride ions and sulfate ions is exerted. The concentration of nitrate ions in the liquid phase Is 500 ppm to 2500 ppm (8 to 40.3 mmol / L), and the selectivity between chloride ions and sulfate ions is most exhibited when the nitrate ion concentration of the solution is 1250 ppm (20.2 mmol / L). ) Was also revealed.

  From the above results, it was revealed that chloride ions and sulfate ions can be separated by column chromatography. Further, it is clear that the concentration of nitric acid in the eluent is preferably adjusted so that the concentration of the liquid phase in contact with the filler is 500 ppm to 2500 ppm, and more preferably adjusted to 1250 ppm. It became.

(Example 2)
Column chromatography was performed on the test sample, and the separation of chloride ion and sulfate ion was examined.

(1) Experimental apparatus An experiment was performed using the column chromatography apparatus 1 shown in FIG. Fill the acrylic column tube 2 (inner diameter 1 cm, height 30 cm, hereinafter simply referred to as column) with a filler 3 (same as the filler used in Example 1) so that the packing height is 10 cm. Then, both ends of the column 2 were closed with the filter 4. The filter 4 was an AS resin filter (Daicel Chemical Industries, trade name Pearlcon filter M80) having a pore diameter of 10 to 30 μm. A test sample was stored in the first tank 5, and an eluent or pure water was stored in the second tank 6. By switching the valve 10a, it is selected whether the liquid stored in the first tank 5 or the liquid stored in the second tank 6 is to be sent, the valve 10b is opened, and the metering pump 7 (solenoid-driven metering pump (Takumina) Manufactured, manufactured by PZD-30R)), and the target stored liquid was dropped into the column 2. The liquid phase in the column was allowed to flow down by opening the valve 10c. The liquid phase flowing down from the column was collected by the fraction collector 8 every predetermined amount. In FIG. 3, a valve 10e is a valve for adjusting the liquid level of the liquid phase in the column 2. In addition, when bubbles were generated in the packing region of the packing material 3, the column 2 was shaken lightly to remove the bubbles from the packing region of the packing material 3, and this was extracted by the air bleeding valve 10d. In the present example, considering the workability when removing bubbles, the filter 4 is provided at both ends of the column 2 to prevent the packing material 3 from jumping out of the column 2. Needless to say, the filter 4 provided at the upper end of the column 2 is not necessary in the essential sense of performing the above. In addition, it is important for the filter 4 provided at the lower end of the column 2 that the liquid permeability can be secured and the chemical resistance is ensured while the filler 3 is held in the column 2. Needless to say, the material is not limited to those described above as long as it can withstand 2.0 mol / L nitric acid, which is considered to have the highest influence by the column method.

  In this example and the following examples, when a small amount (about 10 mL) of the test sample was added to the column 2, it was added directly to the column 2 without using the metering pump 7.

(2) Experimental method 2 mL of the same test sample as in Example 1 was directly added to the column 2. At this time, no color change was observed in the filler 3.

  In order to wash away the droplets of the test sample that may have adhered to the inner wall of the column 2 and cause the sample 3 to be adsorbed on the filler 3, the wall surface of the column 2 above the filler 3 was washed with 1.0 mL of pure water. For the pure water accumulated above the filling height of the filler 3, the valve 10 e was opened, and the liquid level was lowered to the level at which the filling height of the filler 3 passed. This operation was repeated three times, and the pure water poured into the fourth time was left in the column 2 as it was.

  A 2000 ppm nitric acid solution was accommodated in the second tank 6 as an eluent, the valve 10 a was switched to the second tank 6 side, the valve 10 b was opened, and the eluent was dropped into the column 2 by the metering pump 7. The dropping flow rate was controlled at 2.0 mL / min. During this time, the valve 10c was opened, and the liquid flowing down from the lower part of the column 2 was collected by the fraction collector 8 for each predetermined liquid amount.

Chloride ion concentration and sulfate ion concentration collected by the fraction collector 8 were analyzed by ICP-MS. In addition, in the concentration evaluation of sulfate ions (the actual measurement is sulfur atoms decomposed by plasma), Xe gas is flowed during measurement to reduce the effect of ¹⁶ O on ³² S and improve detection sensitivity. I let you. The lower limit of quantification of chloride ion and sulfate ion was 50 ppb and 30 ppb (in terms of sulfate ion), respectively.

(3) Experimental Results FIG. 4 shows the relationship (chromatogram) of the eluent drop amount with respect to chloride ion concentration and sulfate ion concentration. Since the amount of eluent dropped into column 2 was about 250 mL, the peak of sulfate ion could not be completely captured, but the peak top of chloride ion and the peak top of sulfate ion were clearly separated. It became clear that. From this, it was shown that chloride ion and sulfate ion can be separated by column chromatography. In addition, when the total peak amount (entire peak area) was obtained, the chloride ion recovery rate was 100% with respect to the added amount, and it was revealed that the chloride ion recovery rate by this method was extremely high.

(Example 3)
In order to analyze 36Cl / Cl by AMS, about 10 mg of silver chloride precipitate (corresponding to 2.5 mg of chloride ion) is required. In this example, the required amount of silver chloride precipitation was given a margin, and 10 mg of chloride ions was the recovery target. In order to achieve this target amount, it is necessary to process 100 mL of a test sample containing 100 ppm of chloride ions. For this reason, in order to grasp the quantity of the test sample which can be processed with the filler 3 having the inner diameter of 1 cm and the height of 10 cm (same as the filler used in Example 1), the column chromatography is performed according to this quantity. It is necessary to scale up the system. Therefore, a test for comparing the peak shapes of chromatograms was performed using the same experimental method as in Example 2 with the test samples being 1 mL, 10 mL, and 100 mL.

  When the experiment was conducted with 1 mL and 10 mL test samples, the test samples were poured directly onto the column. 100 mL of the test sample is stored in the first tank 5 and dropped onto the column 2 by the metering pump 7, so that all chloride ions and sulfate ions that may remain in the tube flow to the column 2. After dropping, pure water having a volume about 3 times the volume in the tube connecting the pump and the column was poured, and then the eluent was dropped.

  The results are shown in FIG. As is clear from FIG. 5, the peak shape shifts in the direction in which the amount of the eluent increases as the amount of the test sample increases, but the shift is several tens of mL even when 1 mL and 100 mL are treated. It remained to the extent.

  Here, the peak shapes of chloride ions and sulfate ions when 100 mL of the test sample is processed are shown in FIG. FIG. 7 shows an enlarged view of the encircled portion in FIG. The peak of chloride ion and sulfate ion was clearly separated, and it became clear that 100 mL of the test sample could be processed sufficiently.

  From the above results, it was found that in order to obtain a sufficient amount of chloride ions for the analysis of 36Cl / Cl, it is sufficient to pack the packing material 3 in the column 2 having an inner diameter of 1 cm to a packing height of about 10 cm. .

Example 4
Column chromatography tests were conducted under various conditions, and various studies were conducted regarding conditions suitable for separation of chloride ions and sulfate ions.

  First, the same test as in Example 3 was performed by fixing the nitric acid concentration of the nitric acid solution to 2000 ppm and changing the filling height of the filler 3 from 10 cm to 15 cm. As a result, by increasing the packing height of the filler 3, the peak of chloride ions and sulfate ions shifted to the direction in which the eluent increased. As compared with the case where the filling height was 10 cm, no significant improvement was observed.

  Then, the same test as in Example 3 was performed by fixing the filling height of the filler 3 to 15 cm and changing the nitric acid concentration of the nitric acid solution to 2000 ppm, 1500 ppm, and 1000 ppm. The results are shown in FIG. It was found that the lower the concentration of nitric acid in the nitric acid solution, the greater the separation between the chloride ion and sulfate ion peaks, and the better the separation. Also, if the nitric acid concentration in the nitric acid solution is 1000 ppm, the sulfate ion peak is not detected, but the chloride ion peak spreads, and 500 mL or more of eluent is flowed in order to completely recover the chloride ion. It was found that the processing time and the amount of waste liquid increase because of the necessity.

  Therefore, it was determined that it is most appropriate to use a nitric acid solution having a nitric acid concentration of 1500 ppm as an eluent in consideration of improvement in separability and processing time. In addition, as for the filling height of the filler 3, it is advantageous to have a high height in dealing with a dilute solution, and the processing time is about 6 hours even when the height is 15 cm. A test of changing the nitric acid concentration of the nitric acid solution at a length of 10 cm was not performed, and a condition of a height of 15 cm was adopted.

As a result of repeating the above studies, it was found that chloride ions and sulfate ions can be completely separated under the following conditions, the amount of waste liquid can be suppressed, and the processing time can be suppressed to about 6 hours.
-Resin packing height: 15 cm (inner diameter 1 cm column, resin partial volume 11.78 cm3)
・ Resin: Nitrogen ion replacement product of Dowex 1 × 8 (particle size 200-400 mesh) ・ Eluent: 1500 ppm nitric acid ・ Test sample dropping speed: 2.0 mL / min ・ Elution droplet dropping speed: 2.0 mL / min

  When column chromatography is carried out under the above conditions, the peak of chloride ions is completely within the range of 150 to 350 mL of elution droplet amount. On the other hand, the sulfate ion peak appears when the eluent is flowed in an amount of 500 mL or more (FIG. 8). For this reason, when column chromatography is performed, by obtaining a fraction in the range of 150 to 350 mL of elution droplets, sulfate ions can be completely eliminated and chloride ions can be recovered 100%.

(Example 5)
Using a dilute solution having a chloride ion concentration of 1 ppm as a test sample, the applicability of the method of the present invention to the dilute solution was examined. Table 1 shows the test conditions.

  The test results are shown in FIG. It was clarified that there was no significant change in the peak shape of chloride ion and sulfate ion depending on the test conditions, and that the peak appeared at almost the same elution droplet amount. This result shows that 10000 mL of the test sample having a chloride ion concentration of 1 ppm can be processed under the same conditions as when 100 mL of the test sample having a chloride ion concentration of 100 ppm is processed.

  From the above, it was revealed that the separation method of the present invention can be applied to dilute solutions having a chloride ion concentration of about 1 ppm, which could not be applied to the conventional barium sulfate method.

  It is also clear that chloride ions (1 ppm) contained in a 10,000 mL test sample can be recovered 100% as a fraction in the range of 150-350 mL of elution droplets, so that chloride ions can be recovered by concentrating to 50 ppm. It became.

(Example 6)
A simulated sample close to actual groundwater was prepared, and an AMS analysis value of 36Cl / Cl was compared between the conventional method using the barium sulfate method and the method using column chromatography of the present invention.

(1) Preparation of simulated sample In order to make the simulated sample close to the actual groundwater, a liquid obtained by leaching the components of rock pore water was used. A rock core (collection depth 30 m) obtained in the Marlee district of the Australian Otsui Basin was pulverized, and about 200 g of rock particles pulverized to about 1 cm were put in 1 L of polybin. About 1 L of pure water was added to the polybin and allowed to stand for 4 days with a handshake once a day. The inventor of the present application has conducted similar tests in the past (Kotaro Nakada, Takahiro Oyama, Takuma Hasegawa, “Relationship between pressure and water quality in compressed extraction-behavior of major anions and cations”, Autumn Ground Water Society, 2007 From the results of the lecture proceedings, p33), it was speculated that pore water components could be extracted sufficiently by immersion for about 4 days.

  Four days later, the supernatant solution was filtered through a 0.45 μm filter (ADVANTEC, DISMIC25AS045AS) made of cellulose mixed ester to obtain a filtrate. The chloride ion concentration in the obtained solution was about 1400 ppm. The filtrate was diluted with pure water, and the reagent sodium sulfate was added to adjust the chloride ion and sulfate ion concentrations to 100 ppm. The composition of the simulated sample is shown in Table 2.

(2) Sample preparation for analysis by barium sulfate method Each 200 mL sample was divided into three containers and made acidic by adding nitric acid, and then a silver nitrate aqueous solution was added to each container to obtain a precipitate containing silver chloride. . The obtained precipitate was purified by the conventional barium sulfate method described above to obtain a silver chloride precipitate as a sample for AMS analysis, which was subjected to AMS measurement.

(3) Sample preparation for analysis by the method of the present invention (utilizing column chromatography) 100 mL of the simulated sample was subjected to column chromatography under the following conditions obtained in Example 4, and after dropping into the elution droplet, 0 to 150 mL, 150 to 350 mL Were obtained as samples.
-Resin packing height: 15 cm (inner diameter 1 cm column, resin partial volume 11.78 cm3)
・ Resin: Nitrogen ion replacement product of Dowex 1 × 8 (particle size 200-400 mesh) ・ Eluent: 1500 ppm nitric acid ・ Test sample dropping speed: 2.0 mL / min ・ Elution droplet dropping speed: 2.0 mL / min

  Thereafter, 200 mL of 2.0 mol / L nitric acid was dropped on the column for washing, and this dripping liquid was also collected as a sample. The obtained solution was evaluated for chloride ion concentration and sulfate ion concentration by ICP-MS.

  In addition, 100 mL of the simulated sample was added to the above-treated two samples, and the sample prepared by diluting the simulated sample 100 times and using 10000 mL of the solution having a chloride ion concentration of about 1 ppm for column chromatography was also prepared. did.

  Table 3 shows the results of analyzing the chloride ion concentration and sulfate ion concentration of these samples by ICP-MS. The recoveries in Table 3 are expressed as a percentage of the amount of chloride ions or sulfate ions in the eluent (the fraction flowing down the column 2) relative to the amount of chloride ions or sulfate ions in the added solution. In addition, “-” in Table 3 indicates that it is below the lower limit of quantification of ICP-MS. As can be seen from Table 3, in both cases, neither chloride ion nor sulfate ion was detected in the range of nitric acid dropping amount 0-150 mL, 100% chloride ion was detected in 150-350 mL, and 2.0 mol / Almost 100% of sulfate ion was detected from L nitric acid. From this result, the method of the present invention using column chromatography is sufficiently applicable even in a solution composition close to actual groundwater, and the nitric acid concentration of the eluent is 1500 ppm, and a sample is obtained in a nitric acid dropping amount of 150 to 350 mL. You can see that In addition, almost 100% of sulfate ions were recovered in 200 mL of 2.0 mol / L nitric acid, and it became clear that the column can be reused for separation of chloride ions and sulfate ions by performing this washing. .

  A silver nitrate solution was added to these samples to obtain a silver chloride precipitate as a sample for AMS analysis, which was subjected to AMS measurement.

(4) Analysis result of 36Cl / Cl Table 4 shows the analysis value of 36Cl / Cl obtained by subjecting the sample for analysis to AMS measurement. Column-3 is a measurement result of a sample in which 10000 mL of a solution having a chloride ion concentration of about 1 ppm was subjected to column chromatography. In Table 4, the count value judged to be a count derived from 36S on the detector of the accelerator is also shown.

  The count value derived from 36S shows a stable and lower value in the analytical sample prepared by the method of the present invention than in the analytical sample prepared by the barium sulfate method. It was revealed that 36S contained in the prepared analytical sample was low. From this, it was shown that the present invention is superior to the conventional method of barium sulfate as a method for separating 36Cl-containing chloride ions and 36S-containing sulfate ions.

  In the measurement results of this example, there was no significant difference in the value of 36Cl / Cl between the analytical sample prepared by the method of the present invention and the analytical sample prepared by the barium sulfate method. . This is because the 36Cl / Cl value of the sample used in the measurement in this example was relatively large and the count number of 36Cl was large, so even if there was a component incorrectly counted as 36Cl in 36S, there was an effect. This is presumably due to the small number.

  As described above, the separation method of the present invention can reliably separate the 36Cl-containing chloride ions from the 36S-containing sulfate ions, and the separation ability thereof is superior to that of the conventional barium sulfate method. In addition, according to the method of the present invention, the processing time is about 6 hours, which is overwhelmingly short compared to the conventional method, and does not include processing depending on the subjectivity, skill, skill level, etc. of the worker. Therefore, the reproducibility is extremely high as compared with the conventional method, and it is possible to deal with a dilute solution that cannot be applied by the conventional method. That is, it can be said that this technique is overwhelmingly superior to the conventional method not only in terms of separation performance but also in terms of processing time and work simplicity.

  The separation method of the present invention and the sample preparation method for AMS analysis are more preparatory than the conventional pretreatment for 36Cl / Cl analysis of groundwater in geological formations in various regions around the world whose groundwater age has not yet been clarified. As a simple and highly accurate technology, it is an extremely useful technique for clarifying the groundwater flow state in the geological formations of various regions around the world and for clarifying the mechanism of environmental pollution.

3 Filler

Claims (4)

By performing column chromatography on the test sample using a strongly basic anion exchange resin whose counter ion is an anion other than chloride ion as a filler, ³⁶ Cl-containing chloride ions in the test sample are obtained. ^A method for separating ³⁶ Cl-containing chloride ions, comprising separating from ³⁶ S-containing sulfate ions. 2. The separation method according to claim 1, wherein a nitric acid solution is used as an eluent, and a concentration of the nitric acid solution is set to a concentration at which a concentration of nitrate ions in a liquid phase in contact with the packing material can be maintained at 500 to 2500 ppm in the column chromatography. . The separation method according to claim 2, wherein the counter ion is a nitrate ion. The ³⁶ Cl-containing chloride ions separated from the ³⁶ S-containing sulfate ions are reacted with silver ions by the separation method according to claim 1 to produce ³⁶ Cl-containing silver chloride. To prepare a sample for accelerator mass spectrometry.