A method for detecting specific activity of c14 barium carbonate

Abstract

This invention discloses a method for detecting the specific activity of C14 barium carbonate, belonging to the field of radioactivity detection technology. The method includes: dissolving a C14 barium carbonate sample in a weak acid solution to generate a test solution containing bicarbonate ions; then directly mixing the test solution with a scintillation fluid to obtain a scintillation sample; finally, measuring its radioactivity activity using a liquid scintillation counter and calculating the specific activity based on a standard curve. This invention uses a weak acid to dissolve the C14 barium carbonate sample to generate a test solution containing bicarbonate ions that is directly mixed with the scintillation fluid, omitting the alkaline absorption step and simplifying the detection process from four steps in existing methods to two steps. Furthermore, it eliminates the need for a sealed gas absorption device, removing accumulated errors during sample transfer and the additional background introduced by the alkaline solution. Therefore, this invention reduces equipment requirements and improves detection accuracy and ease of operation.

Description

Technical Field

[0001] This application belongs to the field of radioactive detection technology, specifically relating to a method for detecting the specific activity of C14 barium carbonate. Background Technology

[0002] Carbon-14 is a radioactive isotope with an extremely long half-life, making it widely used in archaeological dating, environmental monitoring, and biomedical tracing. Barium carbonate (C14) is a common compound form of C14, and accurate determination of its specific activity is of great significance for related research and applications.

[0003] In existing technologies, the specific activity of C14 barium carbonate is typically detected using the hydrochloric acid dissolution-alkaline absorption-liquid scintillation counting method. The basic principle of this method is as follows: the C14 barium carbonate sample is dissolved in hydrochloric acid, releasing CO2 gas in the reaction. The CO2 is then absorbed by an alkaline solution (such as NaOH solution), converting it into carbonate or bicarbonate. Finally, the absorption solution is mixed with a scintillation liquid, and the radioactivity is measured using a liquid scintillation counter.

[0004] However, this method has the following technical drawbacks: First, the detection process is cumbersome, requiring multiple steps such as "hydrochloric acid dissolution, CO2 gas transfer, alkaline absorption, and absorption liquid transfer." Sample transfer is involved between each step, which can easily lead to cumulative errors. Second, the equipment requirements are high, requiring a sealed gas absorption device, which is complex to operate. Third, the alkaline solution itself may contain radioactive impurities, leading to increased background levels. Furthermore, chemical quenching may occur when the alkaline solution is mixed with the scintillation liquid, affecting the counting efficiency.

[0005] Therefore, developing a simplified, highly accurate, and low-requirement method for detecting the specific activity of C14 barium carbonate is of significant practical importance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting the specific activity of C14 barium carbonate, which solves the technical problems of high equipment requirements, cumbersome operation, and additional measurement errors introduced by the alkali solution due to the need for an alkaline absorption step in the prior art.

[0007] To achieve the above objectives, the present invention provides a method for detecting the specific activity of C14 barium carbonate, the method comprising the following steps: S100. Dissolve the C14 barium carbonate sample with a weak acid solution to obtain a test solution containing bicarbonate C14. The dissolution process is carried out in an open system and does not require a gas absorption device. S200: The test liquid obtained in step S100 is directly mixed with the pre-prepared scintillation liquid to obtain a scintillation sample; S300. Place the scintillation sample obtained in step S200 into a liquid scintillation counter to determine its radioactivity, and calculate the specific activity of C14 barium carbonate according to the standard curve.

[0008] As a preferred technical solution, in step S100, the weak acid is acetic acid, and the concentration of the weak acid solution is 0.3-2 mol / L, preferably 0.5-1.5 mol / L, and more preferably 1 mol / L. In this technical solution, if the acetic acid concentration is too low, the C14 barium carbonate sample will not dissolve completely; if the acetic acid concentration is too high, it may cause the generated barium bicarbonate to further decompose, thereby producing CO2.

[0009] As a preferred technical solution, the volume-to-mass ratio of the weak acid solution to the C14 barium carbonate sample is controlled at 1-5 mL / mg.

[0010] As a preferred technical solution, the weak acid solution is prepared using analytical grade or superior grade reagents.

[0011] As a preferred technical solution, the C14 barium carbonate sample is dissolved in a weak acid solution at room temperature for 5-30 minutes, supplemented by stirring or ultrasonic treatment.

[0012] As a preferred technical solution, the pre-prepared scintillation fluid is a scintillation fluid suitable for water-soluble samples, and the volume ratio of the test solution to the scintillation fluid is 1:5-20, preferably 1:5-10.

[0013] As a preferred technical solution, the liquid scintillation counter is a Tri-Carb series or LSC-LB7 type liquid scintillation counter with a counting time of 10-60 minutes.

[0014] As a preferred technical solution, the standard curve establishment steps are as follows: take a C14 barium carbonate standard with known specific activity, and perform the test according to the same steps as the sample to be tested, and establish a standard curve based on the correspondence between radioactivity and specific activity.

[0015] As a preferred technical solution, the weak acid is ammonium acetate buffer. The method includes: dissolving the C14 barium carbonate sample in 5%-10% ammonium acetate buffer and preparing a test solution with a concentration of 0.01-0.02 mg / mL; then mixing 50-100 μL of the test solution with 5-10 mL of scintillation fluid, so that the mixing volume ratio of the test solution to the scintillation fluid is 1:100-1:200; finally, measuring the radioactivity using a liquid scintillation counter for a counting time of 30-120 seconds.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: (1) The present invention uses a weak acid instead of the traditional hydrochloric acid to dissolve the C14 barium carbonate sample, and reacts to generate a test solution containing barium bicarbonate that is directly mixed with the scintillation liquid. This effectively simplifies the detection process and integrates the original multiple steps of "dissolution, gas transfer, alkaline absorption and absorption liquid transfer" into two steps of "dissolution and direct detection". This eliminates the loss and pollution risk during the sample transfer process and improves the detection accuracy and efficiency.

[0017] (2) The detection method provided by the present invention does not require a sealed gas absorption device, thereby reducing equipment requirements; at the same time, no alkali solution needs to be added during the detection process. Since the alkali solution itself may contain radioactive impurities, and chemical quenching may occur when the alkali solution is mixed with the scintillation liquid, the additional error source introduced by the alkali solution absorption is eliminated from the source, and the detection accuracy and stability are further improved.

[0018] (3) Optionally, the present invention may also use ammonium acetate buffer as a weak acid, which can further shorten the detection time and improve the counting efficiency. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for detecting the specific activity of C14 barium carbonate according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and technical effects of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings, multiple embodiments, and comparative examples.

[0022] like Figure 1 As shown, this invention provides a method for detecting the specific activity of C14 barium carbonate, the method comprising the following steps: S100. Dissolve the C14 barium carbonate sample with a weak acid solution to obtain a test solution containing bicarbonate C14. The dissolution process is carried out in an open system and does not require a gas absorption device. S200: The test liquid obtained in step S100 is directly mixed with the pre-prepared scintillation liquid to obtain a scintillation sample; S300. Place the scintillation sample obtained in step S200 into a liquid scintillation counter to determine its radioactivity, and calculate the specific activity of C14 barium carbonate according to the standard curve.

[0023] In the above embodiments, the weak acid is acetic acid, and the concentration of the weak acid solution is 0.3-2 mol / L. The weak acid solution is prepared using analytical grade or superior grade reagents, and the C14 barium carbonate sample is dissolved in the weak acid solution at room temperature for 5-30 minutes. The dissolution process is supplemented by stirring or ultrasonic treatment.

[0024] In the above embodiments, the scintillation fluid is a scintillation fluid suitable for water-soluble samples, the volume ratio of the test solution to the scintillation fluid is 1:5-20, the liquid scintillation counter is a Tri-Carb series or LSC-LB7 type liquid scintillation counter, and the counting time is 10-60 minutes.

[0025] In the above embodiments, the standard curve establishment steps are as follows: take a C14 barium carbonate standard with known specific activity, perform the test according to the same steps as the sample to be tested, and establish a standard curve based on the correspondence between radioactivity and specific activity.

[0026] In some embodiments, when the weak acid is ammonium acetate buffer, the method includes: dissolving the C14 barium carbonate sample in 5%-10% ammonium acetate buffer and preparing a test solution with a concentration of 0.01-0.02 mg / mL; then mixing 50-100 μL of the test solution with 5-10 mL of scintillation fluid to make the volume ratio of the test solution to the scintillation fluid 1:100-1:200; and finally determining the radioactivity using a liquid scintillation counter for a counting time of 30-120 seconds.

[0027] To further illustrate the working principle and technical effects of the present invention, the following example uses the detection method provided by the present invention and the existing technology (hydrochloric acid dissolution-alkaline absorption-liquid flash detection method) to conduct specific activity detection on the same batch of C14 barium carbonate samples.

[0028] Example 1 1. Instruments and reagents The instruments include: Liquid scintillation counter: Model Tri-Carb 4910 TR, technical specifications include: can hold 408 20ml sample vials or 720 4 / 7ml sample vials, fully automated measurement, 24-hour repeatability stability <0.2%; Electronic balance: Model Mettler Toledo XS105DU, accuracy 0.01 mg; Ultrasonic cleaner: 100-200 W power; Micropipette: Volume range 100-1000 μL; Sample vial: 20 mL low-potassium glass scintillation vial; Vortex oscillator.

[0029] The reagents include: C14 barium carbonate sample: 1 mg of the sample to be tested; Acetic acid: Analytical grade glacial acetic acid conforming to GB / T 676-2007 standard (purity ≥99.8%), prepared into a 1.0 mol / L acetic acid solution with deionized water before use; Scintillation fluid (Ultima Gold AB): Suitable for water-soluble samples, with good quenching resistance; Deionized water.

[0030] 2. Testing Steps S100. Dissolve the C14 barium carbonate sample in a weak acid solution to obtain a test solution containing bicarbonate C14. The reaction between the weak acid and the C14 barium carbonate sample does not generate CO2. In this step, the acetic acid solution is prepared as follows: Take 6.0 mL of analytical grade glacial acetic acid (purity ≥99.8%), dilute to 100 mL with deionized water to prepare an acetic acid solution of about 1.0 mol / L, and then use acid-base titration to determine the accurate concentration of the acetic acid solution. The dissolution process is as follows: Weigh 1 mg of C14 barium carbonate sample and place it in a 20 mL scintillation bottle. Add 1 mL of 1.0 mol / L acetic acid solution to the scintillation bottle to make the volume-to-mass ratio of acetic acid solution to C14 barium carbonate sample 1 mL / mg. Then, tighten the cap and place the bottle on a vortex mixer and shake for 10 minutes. Finally, sonicate the sample in an ultrasonic cleaner for 5 minutes to ensure complete dissolution. The dissolution reaction equation is as follows: Ba 14 CO3 + 2CH3COOH → Ba(HCO3)2+ (CH3COO)2Ba Because dilute acetic acid is used instead of hydrochloric acid in the traditional dissolution process, the dissolution reaction produces soluble barium bicarbonate, which does not release CO2 gas. During the dissolution process, no bubbles are observed in the bottle, and the solution is colorless and transparent.

[0031] S200: Mix the test liquid obtained in step S100 with the pre-prepared scintillation liquid to obtain a scintillation sample; The specific steps are as follows: Add 10 mL of Ultima Gold AB scintillation solution to the solution obtained in step S100, so that the volume ratio of the test solution to the scintillation solution is 1:10; then tighten the cap and place it on a vortex shaker to mix thoroughly for 1 minute to ensure that the sample and the scintillation solution are completely mixed and to avoid phase separation. Finally, let the prepared scintillation sample stand for 30 minutes under light-protected conditions to eliminate possible chemiluminescence interference.

[0032] S300. Place the scintillation sample obtained in step S200 into a liquid scintillation counter to determine its radioactivity, and calculate the specific activity of C14 barium carbonate according to the standard curve.

[0033] This step specifically includes: (1) Counting detection (11) Preheat and stabilize the liquid scintillation counter for 30 minutes, set the 14C measurement window to 0-156 keV, put the obtained scintillation sample into the sample transfer tray, set the counting time to 30 minutes, repeat the measurement 3 times for each sample, and take the average value. (12) Set up a blank control group: Mix 1 mL of 1.0 mol / L acetic acid solution with 10 mL of scintillation solution, and measure the count of the blank control group under the same conditions as in step (11); (2) Establishing a standard curve Take a C14 barium carbonate standard with a known specific activity (specific activity value of 1 μCi / mg), weigh 0.5 mg, 1.0 mg, 1.5 mg and 2.0 mg respectively, and perform the detection according to the above steps S100, S200 and step (11). Plot a standard curve with radioactivity (cpm) as the vertical axis and specific activity (μCi / mg) as the horizontal axis.

[0034] (3) Calculate specific activity The specific activity of the test sample is calculated based on the net count rate of the test sample.

[0035] Example 2 Example 2 is basically the same as Example 1, except that: The concentration of the acetic acid solution is 0.3 mol / L; The amount of C14 barium carbonate sample used was 0.5 mg; The time for dissolving the C14 barium carbonate sample in acetic acid was 5 minutes. The volume-to-mass ratio of acetic acid solution to sample is 2 mL / mg (i.e., 1 mL of acetic acid solution is added). The volume ratio of the test solution to the scintillation fluid is 1:5 (the amount of scintillation fluid added is 1.25 mL). The counting time is 10 minutes.

[0036] Example 3 Example 3 is basically the same as Example 1, except that: The acetic acid solution concentration is 2 mol / L; The amount of C14 barium carbonate sample used was 2.0 mg; The volume ratio of acetic acid solution to sample is 5 mL / mg (i.e., 10 mL of acetic acid solution is added). The volume ratio of the test solution to the scintillation fluid is 1:20 (the amount of scintillation fluid added is 200 mL, and a large-volume scintillation bottle is required). The scintillation fluid counting time is 60 minutes.

[0037] Example 4 This embodiment provides a method for detecting the specific activity of C14 barium carbonate based on an ammonium acetate buffer system. The aim is to maintain a stable pH environment through the buffer solution, and to further reduce the chemical quenching effect caused by the continuous decrease in pH value by high-dilution injection, thereby shortening the detection time and improving the detection efficiency.

[0038] 1. Instruments and reagents Instrumentation: Basically the same as in Example 1, the liquid scintillation counter is model Tri-Carb 4910 TR.

[0039] The reagents include: C14 barium carbonate sample: 1.5 mg of the sample to be tested; Ammonium acetate: Analytical grade ammonium acetate conforming to GB / T 1292-2008 standard (purity ≥98.0%). When using, prepare a 7% ammonium acetate solution (approximately 0.91 mol / L) with deionized water. Scintillation fluid: Ultima Gold AB, suitable for water-soluble samples; Deionized water.

[0040] 2. Testing Procedures S100. Dissolve the C14 barium carbonate sample in ammonium acetate buffer solution to obtain a test solution containing bicarbonate ions. Specifically, 1.5 mg of C14 barium carbonate sample was accurately weighed and placed in a 100 mL volumetric flask. 7% ammonium acetate buffer was added to dissolve and dilute to the 100 mL mark. The solution was then shaken well to obtain a test solution with a concentration of 0.015 mg / mL. In this step, the acetate ions in the ammonium acetate buffer react with the barium carbonate to form soluble barium bicarbonate. Simultaneously, ammonium ions and bicarbonate ions form a buffer pair, thus maintaining the pH stability of the solution and preventing CO2 release. No bubbles were observed during the dissolution process.

[0041] S200: Mix the test liquid obtained in step S100 with the pre-prepared scintillation liquid to obtain a scintillation sample; Specifically, measure 7 mL of scintillation fluid into a 7 mL scintillation bottle, accurately add 60 μL of the above-mentioned test solution, so that the volume ratio of the test solution to the scintillation fluid is 1:117, and shake well to obtain the scintillation sample.

[0042] S200' Preparation of blank solution: Measure 7 mL of scintillation fluid into a 7 mL scintillation bottle, accurately add 60 μL of 7% ammonium acetate buffer, and shake well to obtain the blank solution.

[0043] S300, Liquid Scintillation Detection (1) Instrument parameter settings: Preheat and stabilize the liquid scintillation counter for 30 minutes, set the C14 measurement window to 0-156keV, set the coincidence time to 35 ns, and select the C-14 isotope mode for detection; (2) Counting detection: Take the prepared scintillation sample and blank solution and put them into the sample transfer tray respectively. Set the counting time to 60 seconds. Repeat the measurement 3 times for each sample, take the average value, record the count rate of the scintillation sample and the count rate of the blank solution, and calculate the net count rate. (3) Specific activity calculation: Calculate the specific activity of the sample based on the standard curve.

[0044] Comparative Example 1 The existing technology (hydrochloric acid dissolution-alkaline absorption-liquid scintillation detection method) was used to test the C14 barium carbonate sample (from the same batch as the C14 barium carbonate sample in Example 1). The specific steps are as follows: (1) Accurately weigh 1 mg of C14 barium carbonate sample, place it in a reaction flask, add 1 mL of 1 mol / L hydrochloric acid solution, and the reaction releases CO2 gas; (2) The released CO2 gas was absorbed with 5 mL of 0.5 mol / L NaOH solution; (3) Take 1 mL of the absorption solution and mix it with 10 mL of scintillation solution for liquid scintillation detection; (4) Repeat the measurement 3 times and calculate the specific activity.

[0045] Test results The detection results of Examples 1-4 and Comparative Example 1 are shown in Table 1 (Note: The parameter optimization of Example 4 is aimed at improving stability, and its recovery rate should be similar to that of Examples 1-3 and better than that of Comparative Example 1).

[0046]

[0047] As shown in Table 1, the measured specific activities of Examples 1-4 all reached above 0.96, indicating that the detection method provided by this invention is significantly superior to the 0.92 μCi / mg of the prior art (Comparative Example 1). Furthermore, the absolute values ​​of the relative deviations of Examples 1-4 are also significantly lower than those of Comparative Example 1. This demonstrates that by using a weak acid (acetic acid or ammonium acetate) instead of the hydrochloric acid dissolution of the prior art, this invention completely eliminates the alkaline absorption step, removes the additional errors introduced by the alkaline solution, and effectively improves the detection accuracy.

[0048] The measured specific activity of Example 1 (acetic acid concentration of 1.0 M) was 0.99 μCi / mg, with a relative deviation of -1.0%. In contrast, the measured specific activities of Examples 2 (acetic acid concentration of 0.3 M) and 3 (acetic acid concentration of 2.0 M) were 0.97 μCi / mg and 0.96 μCi / mg, respectively, with relative deviations of -3.0% and -4.0%. This indicates that Example 1 exhibited the highest measured specific activity and the lowest relative deviation compared to Examples 2 and 3. This demonstrates that when acetic acid is chosen as the weak acid, incomplete dissolution occurs at excessively low concentrations (0.3 M), while excessively high concentrations (2.0 M) may lead to further decomposition of barium bicarbonate, proving that a 1.0 M acetic acid concentration is the preferred concentration. The deviations of Example 1 (counting time of 30 min) and Example 2 (counting time of 10 min) were -1.0% and -3.0%, respectively, indicating that appropriately extending the counting time can improve statistical accuracy. The specific activity measured in Example 4 (weak acid selected ammonium acetate buffer) was 0.99 μCi / mg, with a relative deviation of -2.0%, which was comparable to the accuracy of the optimal Example 1 (acetic acid concentration of 1.0M). However, the counting time in Example 4 was only 60 seconds, much less than the 30 minutes in Example 1. Compared with Example 1, the detection efficiency of Example 4 was improved by 30 times, which fully demonstrates the technical advantages of the ammonium acetate buffer system combined with high dilution (significantly increased organic phase ratio) for sample introduction. At the same time, Example 4 adopted a coincidence time parameter of 35 ns, which further optimized the signal recognition accuracy.

[0049] In summary, this invention, by employing a weak acid dissolution method and omitting the alkaline absorption step, significantly simplifies the operation process, reduces equipment requirements, and eliminates additional errors introduced by the alkaline solution while ensuring detection accuracy. Furthermore, the ammonium acetate buffer solution scheme can substantially shorten the detection time, achieving unexpected technical benefits. Therefore, the detection method provided by this invention is characterized by its ease of operation, low equipment requirements, high detection accuracy, and fast detection speed.

[0050] The above provides a detailed description of a method for detecting the specific activity of C14 barium carbonate. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of these embodiments are merely for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for detecting the specific activity of C14 barium carbonate, characterized in that, The method includes the following steps: S100. Dissolve the C14 barium carbonate sample with a weak acid solution to obtain a test solution containing bicarbonate C14. The dissolution process is carried out in an open system and does not require a gas absorption device. S200: The test liquid obtained in step S100 is directly mixed with the pre-prepared scintillation liquid to obtain a scintillation sample; S300. Place the scintillation sample obtained in step S200 into a liquid scintillation counter to determine its radioactivity, and calculate the specific activity of C14 barium carbonate according to the standard curve.

2. The method for detecting the specific activity of C14 barium carbonate according to claim 1, characterized in that, In step S100, the weak acid is acetic acid, and the concentration of the weak acid solution is 0.3-2 mol / L, preferably 0.5-1.5 mol / L, and more preferably 1 mol / L.

3. The method for detecting the specific activity of C14 barium carbonate according to claim 2, characterized in that, In step S100, the volume-to-mass ratio of the weak acid solution to the C14 barium carbonate sample is controlled to be 1-5 mL / mg.

4. The method for detecting the specific activity of C14 barium carbonate according to claim 3, characterized in that, In step S100, the weak acid solution is prepared using analytical grade or superior grade reagents.

5. The method for detecting the specific activity of C14 barium carbonate according to claim 1, characterized in that, In step S100, the C14 barium carbonate sample is dissolved in a weak acid solution at room temperature for 5-30 minutes, with the addition of stirring or ultrasonic treatment.

6. The method for detecting the specific activity of C14 barium carbonate according to claim 1, characterized in that, In step S200, the pre-prepared scintillation fluid is a scintillation fluid suitable for water-soluble samples, and the volume ratio of the test solution to the scintillation fluid is 1:5-20, preferably 1:5-10.

7. The method for detecting the specific activity of C14 barium carbonate according to claim 1, characterized in that, In step S300, the liquid scintillation counter is a Tri-Carb series or LSC-LB7 type liquid scintillation counter, and the counting time is 10-60 minutes.

8. The method for detecting the specific activity of C14 barium carbonate according to claim 5, characterized in that, In step S300, the standard curve establishment step is as follows: take a C14 barium carbonate standard with known specific activity, and perform the test according to the same steps as the sample to be tested, and establish a standard curve based on the correspondence between radioactivity and specific activity.

9. The method for detecting the specific activity of C14 barium carbonate according to claim 1, characterized in that, The weak acid is ammonium acetate buffer. The C14 barium carbonate sample is dissolved in 5%-10% ammonium acetate buffer to prepare a test solution with a concentration of 0.01-0.02 mg / mL. The mixing volume ratio of the test solution to the scintillation fluid is 1:100-1:

200. The volume of scintillation fluid is 5-10 mL, and the volume of the test solution is 50-100 μL. The counting time is 30-120 seconds.

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