Methanol quenched inhibition type scintillation liquid and its application

Abstract

The present application relates to the technical field of radioactivity detection, and particularly relates to a methanol quenching inhibition type scintillation liquid and application thereof, the methanol quenching inhibition type scintillation liquid comprising: a solvent, an anti-quenching scavenger, a pH buffer, a first scintillator and a second scintillator, wherein the solvent comprises a non-polar main solvent and a polar composite cosolvent; and the anti-quenching scavenger comprises a semicarbazide hydrochloride and a molecular sieve powder.The methanol quenching inhibition type scintillation liquid provided by the present application has good compatibility with a methanol sample, can be directly mixed with the methanol sample for scintillation counting, can effectively inhibit the quenching effect caused by the methanol and sample impurities, and can improve the detection accuracy, while simplifying the detection process and reducing the detection cost.

Description

Technical Field

[0001] This invention relates to the field of radioactivity detection technology, and in particular to a methanol-quenched scintillation suppressor fluid and its application. Background Technology

[0002] Methanol, a commonly used organic liquid, is widely used in fuels, solvents, and chemical raw materials. Green methanol, produced from renewable carbon sources such as biomass, can effectively reduce carbon emissions and has good application potential in the fuel sector. Currently, the industry mainly detects radioactive carbon in methanol samples. 14 C. Determine the proportion of renewable carbon sources in the sample to quantify the blending ratio of green methanol.

[0003] Currently used for 14 The mainstream methods for detecting carbon dioxide are liquid scintillation counting and accelerator mass spectrometry. Traditional liquid scintillation counting requires the combustion of methanol fuel to generate carbon dioxide, which is then mixed with the scintillation liquid after multiple conversion processes. The sample pretreatment process is cumbersome and time-consuming. Although accelerator mass spectrometry has excellent detection sensitivity, the purchase and maintenance costs of the supporting equipment are high, the detection process is complex, and the cost of single-sample analysis remains high, making it difficult to be used in routine detection scenarios with large batches of samples.

[0004] Meanwhile, methanol itself has a chemical quenching effect on conventional scintillation fluids. Directly mixing methanol with general-purpose scintillation fluids for detection can easily cause signal deviation and affect the detection results. 14 The accuracy of C content determination results is crucial. Current technologies lack dedicated scintillation solutions and rapid detection methods that are directly compatible with methanol samples and effectively suppress alcohol quenching effects. This makes it difficult to balance detection efficiency, accuracy, and cost, and thus fails to meet the practical needs of large-scale, rapid, low-cost, and accurate detection in scenarios such as green methanol production, market certification, and regulatory verification. Therefore, developing a detection system that can directly detect methanol samples, effectively mitigate the effects of methanol quenching, and is simple and cost-effective has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To address the aforementioned technical issues, this invention employs a synergistic detection method based on optimized scintillation agent formulation to effectively suppress quenching interference from direct scintillation counting of methanol samples. This simplifies the detection process, reduces detection costs, and simultaneously ensures detection accuracy and efficiency, meeting the needs for rapid, high-volume detection of methanol samples.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a methanol quenching and suppression scintillation fluid, comprising: a solvent, an anti-quenching scavenger, a pH buffer, a first scintillation agent, and a second scintillation agent, wherein the solvent comprises a nonpolar primary solvent and a polar composite co-solvent; and the anti-quenching scavenger comprises aminourea hydrochloride and molecular sieve powder.

[0008] This invention improves the compatibility between scintillation fluid and methanol through a composite solvent system, avoiding the problem of phase separation. Aminourea hydrochloride can remove aldehydes and acidic impurities in methanol samples in situ, while molecular sieve powder selectively adsorbs impurities through physical adsorption, synergistically suppressing the quenching effect. A pH buffer stabilizes the acid-base environment of the system, ensuring the luminescence performance of the scintillation fluid. This invention effectively solves the problems of quenching caused by methanol and sample impurities, as well as the poor compatibility between methanol and conventional scintillation fluids, enabling direct mixing and detection of methanol samples without the need for complex pretreatment such as combustion or conversion.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0010] As a preferred embodiment of the present invention, the volume content of the nonpolar main solvent is 50% to 60% based on the total volume of the methanol quenching and suppression scintillation fluid, for example, it can be 50%, 53%, 56%, 58% or 60%, etc., and the volume content of the polar composite co-solvent is 35% to 50%, for example, it can be 35%, 39%, 43%, 47% or 50%, etc.

[0011] As a preferred embodiment of the present invention, the nonpolar primary solvent includes p-tert-butyltoluene.

[0012] Preferably, the polar composite cosolvent comprises a combination of 1,2-propanediol and ethylene glycol ethyl ether, wherein the volume ratio of 1,2-propanediol to ethylene glycol ethyl ether is (3~8): the volume content of 1,1,2-propanediol is 30~40%, for example, it can be 30%, 33%, 36%, 38% or 40%, etc., and the volume content of ethylene glycol ethyl ether is 5~10%, for example, it can be 5%, 6%, 7%, 8% or 10%, etc.

[0013] This invention utilizes an optimized solvent ratio to ensure the scintillation fluid is fully dissolved and exerts its luminescent efficiency. It also achieves uniform miscibility with methanol fuels of varying water content and impurity levels, completely avoiding stratification and solving the problem of uneven mixing caused by improper solvent ratios. The preferred non-polar main solvent is p-tert-butyltoluene, which exhibits stable optical properties and high quenching tolerance. Combined with a specific ratio of 1,2-propanediol and ethylene glycol ethyl ether to form a composite solvent, it matches the polarity of methanol, enhancing the system's miscibility and further improving detection stability.

[0014] As a preferred embodiment of the present invention, the concentration of the aminourea hydrochloride is 1~5 g / L, for example, it can be 1g / L, 2g / L, 3g / L, 4g / L or 5g / L.

[0015] This invention limits the concentration range of aminourea hydrochloride to neutralize and remove interfering impurities such as aldehydes and acids from methanol. The reasonable concentration ensures the impurity removal effect and does not introduce new quenching interference due to excessive reagent, thus optimizing the anti-quenching effect.

[0016] As a preferred embodiment of the present invention, the concentration of the molecular sieve powder is 2~5 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L, 4.5 g / L or 5 g / L.

[0017] Preferably, the particle size of the molecular sieve powder is 1~3μm, for example, it can be 1μm, 1.5μm, 2μm, 2.5μm or 3μm.

[0018] Preferably, the molecular sieve powder is 3Å molecular sieve powder, and it is activated at high temperature before use. Under dry nitrogen protection, it is activated at 300°C for 4 hours, and then cooled to room temperature in a nitrogen atmosphere and sealed for later use.

[0019] This invention specifies the addition concentration, particle size, and type of molecular sieve powder. The 3Å molecular sieve can capture impurities such as water in methanol through physical adsorption, and its fine particle size can ensure uniform dispersion in the scintillation solution, maintaining the stability of the system's detection performance throughout the process.

[0020] As a preferred embodiment of the present invention, the pH buffer comprises a buffer pair composed of triethanolamine and acetic acid, wherein the total mass concentration of the buffer pair is 0.5~2 g / L, for example, it can be 0.5 g / L, 0.9 g / L, 1.3 g / L, 1.7 g / L or 2 g / L, etc.; the molar ratio of triethanolamine to acetic acid is (1~1.5):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.4:1 or 1.5:1, etc., and the triethanolamine and acetic acid are pre-mixed to prepare a buffer solution before being added.

[0021] As a preferred embodiment of the present invention, the first scintillator includes PPO with a concentration of 6~10g / L, for example, it can be 6g / L, 7g / L, 8g / L, 9g / L or 10g / L.

[0022] Preferably, the second scintillator comprises BIS-MSB at a concentration of 0.15~0.3 g / L, such as 0.15 g / L, 0.19 g / L, 0.23 g / L, 0.27 g / L or 0.3 g / L.

[0023] This invention employs a dual scintillator system consisting of PPO and BIS-MSB. PPO acts as the main scintillator, absorbing radiation energy and emitting fluorescence. BIS-MSB wavelength conversion matches the photoelectric receiving band of the detection device. The combination of the two enhances the optical signal conversion efficiency and the device recognition rate, thereby improving detection sensitivity.

[0024] In a second aspect, the present invention provides an application of the methanol quenching and suppression scintillation fluid as described in the first aspect, including the use of the methanol quenching and suppression scintillation fluid for carbon source detection of methanol fuel.

[0025] As a preferred technical solution of the present invention, the carbon source detection includes: mixing the methanol fuel to be tested and the methanol quenching and suppression scintillation liquid evenly in a detection bottle, allowing it to stand and react, and then performing scintillation counting after cooling and equilibrium.

[0026] As a preferred technical solution of the present invention, the coincidence time window of the scintillation count is set to 8~12ns, for example, it can be 8ns, 9ns, 10ns, 11ns or 12ns, and a 20ns delay is set to enable it, so as to eliminate the interference of fast decaying chemiluminescence.

[0027] Preferably, the counting time is divided into 8 segments, with a 5-minute pause between two adjacent flashing count segments and a slight shaking of the detection bottle.

[0028] Preferably, the settling reaction time is 15 minutes, the cooling equilibrium is carried out in a 4°C refrigerator for 20 hours, and the total time for the scintillation counting is 4 hours.

[0029] Preferably, the carbon source detection further includes the simultaneous detection of a standard methanol sample and a background methanol sample.

[0030] The detection of standard methanol sample and background methanol sample described in this invention is carried out simultaneously with the detection of methanol fuel to be tested. The three test bottles are isolated by a partition with optically blackened aluminum foil to prevent cross-interference. Each test simultaneously obtains the count rate of the methanol sample to be tested, the background count rate, and the count rate of the standard methanol sample.

[0031] Preferably, the test bottle is a low-diffusion polyethylene bottle, with a sealed membrane separating the inner cavity of the bottle. The sealed cavity is pre-filled with the methanol quenching and suppression scintillation fluid. The matching screw cap is provided with spikes. After adding the methanol fuel to be tested into the test bottle and tightening the screw cap, the sealed membrane can be pierced to achieve mixing of the methanol fuel to be tested and the methanol quenching and suppression scintillation fluid.

[0032] The standard methanol sample described in this invention is green methanol with a purity greater than 99.9%, and the background methanol sample is petrochemical methanol with a purity greater than 99.9%. The count rate obtained from the background methanol sample test is the background count rate, and the count rate obtained from the standard methanol sample test is used to calculate the counting efficiency (E), which is verified by the NIST SRM-4990C oxalic acid standard. The specific calculation formula is as follows:

[0033]

[0034] The standard methanol sample count rate and background count rate are both expressed in cpm. 14 The unit for C activity is Bq.

[0035] The proportion of green methanol in methanol fuel (C) GM ) through sample specific activity (A Blend DPM / g(C) and CO2 in modern atmosphere and biomass 14 The C ratio is determined.

[0036]

[0037] In ASTM-D6866, the modern sample activity is defined as 13.56 DPM / g(C), and in 2020, the REF is defined as 1.000.

[0038] The specific activity of a sample is calculated using the following formula:

[0039]

[0040] In the above formula, CPM Blend and CPM Bkgd These are the count rates of the methanol fuel mixture sample and the purified methanol sample, respectively. E is the counting efficiency, and C is the counting rate. Total This is the total carbon mass in the sample, calculated using the following formula:

[0041]

[0042] In the above formula, m Blend It is the mass of the methanol fuel sample, f GM It is the mass fraction of green methanol in the methanol fuel mixture, while w GM and w FM These are the carbon mass fractions of green methanol and fossil methanol, respectively.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) The methanol quenching and suppression scintillation liquid provided by the present invention can be directly mixed with methanol fuel for detection without the need for complex pretreatment steps such as combustion and carbon dioxide conversion, which greatly simplifies the detection process. The detection can be completed by relying on a conventional liquid scintillation counter, which is suitable for large-scale screening of samples, market certification and regulatory verification scenarios.

[0045] (2) The methanol quenching and suppression scintillation fluid provided by the present invention improves the compatibility with methanol through composite solvents, and combines aminourea hydrochloride and molecular sieves to remove impurities and resist quenching, which can significantly suppress chemical quenching and effectively improve the accuracy of detection. Detailed Implementation

[0046] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0047] Example 1

[0048] This embodiment provides a methanol-quenched scintillation inhibitor, comprising, by total volume: 550 mL of p-tert-butyltoluene, 350 mL of 1,2-propanediol, 50 mL of ethylene glycol ethyl ether, 8.0 g of PPO (2,5-diphenyloxazole), 0.25 g of BIS-MSB, 2.5 g of aminourea hydrochloride, 3.0 g of activated 3Å molecular sieve powder, and 1.2 g of triethanolamine. The solution is pre-neutralized with 0.6 g of acetic acid to prepare a buffer solution before being added.

[0049] The methanol quenching and suppression scintillation fluid described above was used for carbon source detection of methanol fuel. The methanol fuel to be tested, green methanol with a purity greater than 99.9%, and petrochemical methanol with a purity greater than 99.9% were used as methanol samples. The methanol fuel to be tested was a known 10% green methanol sample. 5 mL of each sample was added to three low-diffusion polyethylene bottles pre-filled with 15 mL of the methanol quenching and suppression scintillation fluid. The caps were tightened, the sealing film was punctured, and the mixture was vortexed and oscillated until homogeneous. The mixture was allowed to stand for 15 minutes and then transferred to a 4°C refrigerator to cool and equilibrate for 20 hours. The detection mode employed simultaneous parallel detection of the three bottles using a three-tank integrated structure. Three independent low-diffusion polyethylene bottles were embedded within an outer frame and separated by an optical separator (coated with black aluminum foil). A Wallac liquid scintillation spectrometer was used. The Quantulus 1220 is set to a counting coincidence time window of 10ns, with a 20ns delay before counting begins. The total counting time is 4 hours, divided into 8 counting intervals. Each interval is paused for 5 minutes and the sample bottle is gently shaken to complete one counting test. A single test can simultaneously obtain the counting rate of methanol fuel, the counting rate of green methanol, and the background counting rate of petrochemical methanol. The number of tests n is 6.

[0050] In the test results, the background count rate was 2.1±0.3 cpm, the count efficiency was 79.2±1.8%, and the RSD of the green methanol percentage in 6 repeated measurements was 1.7%.

[0051] Example 2

[0052] This embodiment provides a methanol-quenched scintillation inhibitor, comprising, by total volume: 500 mL of p-tert-butyltoluene, 350 mL of 1,2-propanediol, 100 mL of ethylene glycol ethyl ether, 10.0 g of PPO (2,5-diphenyloxazole), 0.30 g of BIS-MSB, 5 g of aminourea hydrochloride, 2.0 g of activated 3Å molecular sieve powder, and 1.2 g of triethanolamine. The solution is pre-neutralized with 0.6 g of acetic acid to prepare a buffer solution before being added.

[0053] The carbon source of methanol fuel was detected using the methanol quenching and suppression scintillation fluid described above. Commercially available M100 methanol fuel (claiming to contain 15% green methanol) was tested using the same carbon source detection method as in Example 1, except that the number of parallel tests was 8. The percentage of green methanol in the 8 repeated tests was 14.8 ± 0.4%, with an RSD of 2.7%. The ASTM D6866 AMS method was used as a reference, and the AMS method value was 15.1 ± 0.2% (RSD = 1.3%).

[0054] Example 3

[0055] This embodiment provides a methanol-quenched scintillation inhibitor, comprising, by total volume: 600 mL of p-tert-butyltoluene, 300 mL of 1,2-propanediol, 50 mL of ethylene glycol ethyl ether, 6.0 g of PPO (2,5-diphenyloxazole), 0.15 g of BIS-MSB, 1 g of aminourea hydrochloride, 5.0 g of activated 3Å molecular sieve powder, 1.2 g of triethanolamine, and 0.6 g of acetic acid, which are pre-neutralized to form a buffer solution before being added.

[0056] The above-mentioned methanol quenching and suppression scintillation fluid was used to detect the carbon source of methanol fuel. The test samples and methods were the same as in Example 2. The green methanol percentage was 14.8 ± 0.4% after 8 repeated measurements, with an RSD of 2.8%.

[0057] Example 4

[0058] This embodiment provides a methanol quenching and suppression scintillation fluid. Except for the addition of 6g of aminourea hydrochloride, it is the same as in Example 1. The RSD of the green methanol content measured in 6 repeated measurements is 2.8%.

[0059] Example 5

[0060] This embodiment provides a methanol-quenched scintillation suppressor fluid. Except for 450 mL of p-tert-butyltoluene and 450 mL of 1,2-propanediol, the rest are the same as in Example 1. The counting efficiency of 6 repeated tests is 60.0 ± 2.5%.

[0061] Example 6

[0062] This embodiment provides a methanol-quenched scintillation suppressor fluid, which is the same as in Example 1 except for 650 mL of p-tert-butyltoluene and 250 mL of 1,2-propanediol. The counting efficiency of 6 repeated tests is 62.0 ± 3.0%.

[0063] Comparative Example 1

[0064] This comparative example provides a scintillation fluid that is identical to that of Example 1 except that it does not contain aminourea hydrochloride and molecular sieve powder.

[0065] Comparative Example 2

[0066] This comparative example used commercially available scintillation fluid Ultima Gold F (Perkin Elmer 6013171), and the test method was the same as in Example 1. The background count rate was 3.6 ± 0.5 cpm, the counting efficiency was 72.5 ± 2.1%, and the RSD of the green methanol percentage in 6 repeated measurements was 3.2%.

[0067] Impurity Tolerance Test Method

[0068] Impurity tolerance tests were conducted on Example 1 and Comparative Example 1. The carbon source of methanol samples containing impurities was detected using the scintillation fluids from Example 1 and Comparative Example 1, respectively. The detection of standard methanol samples and background methanol samples was performed simultaneously with the detection of methanol samples containing impurities. The standard methanol sample was green methanol with a purity greater than 99.9%, and the background methanol sample was petrochemical methanol with a purity greater than 99.9%. The methanol samples containing impurities were made by adding impurities to the standard methanol samples. 5 mL of each sample was added to three low-diffusion polyethylene bottles pre-filled with 15 mL of the aforementioned scintillation fluid. The caps were tightened, the sealing film was punctured, and the mixture was vortexed and oscillated until homogeneous. The mixture was allowed to stand for 15 minutes and then transferred to a 4°C refrigerator to cool and equilibrate for 20 hours. The detection mode employed simultaneous parallel detection of the three bottles using a three-tank integrated structure. Three independent low-diffusion polyethylene bottles were embedded within an outer frame and separated by an optical separator (coated with black aluminum foil). A Wallac Quantulus liquid scintillation spectrometer was used. 1220 sets the counting time window to 10ns, delays the start of counting for 20ns; the total counting time is 4 hours, divided into 8 counting intervals on average. The intervals are paused for 5 minutes and the sample bottle is gently shaken to complete one counting test. A single test can simultaneously obtain the count rate of methanol fuel containing impurities, the count rate of green methanol, and the background count rate of petrochemical methanol. The number of tests n is 6.

[0069]

[0070]

[0071] The impurities were 0.3% formic acid, 0.3% formaldehyde, and 5% water, respectively. The test results are shown in Table 1.

[0072] Test Results

[0073] Table 1

[0074]

[0075] The test results show that:

[0076] (1) As can be seen from Examples 1 to 3, by adding an anti-quenching scavenger to the solvent system, the present invention can achieve good miscibility between scintillation liquid and methanol sample, while effectively inhibiting various types of quenching, ensuring high technical efficiency, test accuracy and stability of detection. Compared with the ASTM D6866 AMS method, the test results have smaller deviations and the detection method is more convenient and suitable for industrial batch sample detection.

[0077] (2) As can be seen from Examples 1 and 4-6, the present invention can achieve better test accuracy by further optimizing the amount of anti-quenching scavenger added and the solvent compounding ratio. Excessive aminourea hydrochloride will cause self-fluorescence interference and increase the RSD of repeated tests. When the proportion of 1,2-propanediol is higher than 40%, the system polarity is too strong and chemical quenching is triggered, and the counting efficiency is significantly reduced. When the proportion of 1,2-propanediol is lower than 30%, the methanol carrying capacity is insufficient and phase separation is triggered, and physical quenching is aggravated.

[0078] (3) As can be seen from Example 1 and Comparative Examples 1 and 2, the present invention, by combining aminourea hydrochloride with 3Å molecular sieve powder activated at high temperature, can obtain excellent resistance to impurity quenching, lower background count, and better detection precision. However, when aminourea hydrochloride and molecular sieve powder are not used, it cannot effectively tolerate common industrial impurities such as formic acid, formaldehyde, and moisture. When commercially available scintillation fluid is used, the counting efficiency and precision are weaker than the system of the present invention. As shown in Table 1, under pure standard samples, the counting efficiency of Example 1 and Comparative Example 1 are similar; however, after adding 0.3% formic acid, 0.3% formaldehyde, and 5% moisture, the counting efficiency of Comparative Example 1 drops significantly, especially when formaldehyde impurities are present, the efficiency drops to 58.40%, while Example 1 is less affected by impurities. This fully demonstrates that aminourea hydrochloride and activated molecular sieve can synergistically adsorb polar impurities and block the quenching reaction caused by impurities, greatly improving the industrial applicability of the system.

[0079] This invention uses aminourea hydrochloride and high-temperature activated 3Å molecular sieve as anti-quenching functional components; the formulation system of synergistic compound solvent takes into account the methanol fuel dissolution carrying capacity, low background, high counting efficiency and strong impurity tolerance. The detection precision is better than that of existing commercially available scintillation fluids. It can be stably applied to the detection of carbon sources of methanol fuel and the quantitative analysis of green methanol proportion. It is suitable for complex impurity samples, simplifies the detection process and reduces the detection time.

Claims

1. A methanol-quenched scintillation suppressor fluid, characterized in that, include: The scintillation agent comprises a solvent, an anti-quenching agent, a pH buffer, a first scintillation agent, and a second scintillation agent. The solvent includes a nonpolar primary solvent and a polar composite co-solvent. The nonpolar primary solvent includes p-tert-butyltoluene, and the polar composite co-solvent includes a combination of 1,2-propanediol and ethylene glycol ethyl ether, with a volume ratio of (3-8):

1. The anti-quenching agent comprises aminourea hydrochloride and molecular sieve powder, wherein the molecular sieve powder is 3Å molecular sieve powder. Based on the total volume of the methanol-quenched scintillation liquid, the volume content of the nonpolar primary solvent is 50%-60%, the volume content of the polar composite co-solvent is 35%-50%, the concentration of the aminourea hydrochloride is 1-5 g / L, the concentration of the molecular sieve powder is 2-5 g / L, the first scintillation agent includes PPO at a concentration of 6-10 g / L, and the second scintillation agent includes BIS-MSB at a concentration of 0.15-0.3 g / L.

2. The methanol quenching and suppression scintillation fluid according to claim 1, characterized in that, The particle size of the molecular sieve powder is 1~3μm.

3. The methanol quenching and suppression scintillation fluid according to claim 1, characterized in that, The pH buffer comprises a buffer pair consisting of triethanolamine and acetic acid, with a total mass concentration of 0.5~2 g / L; the molar ratio of triethanolamine to acetic acid is (1~1.5):

1.

4. The application of the methanol quenching and suppression scintillation fluid as described in any one of claims 1 to 3, characterized in that, This includes using the methanol quenching and suppression scintillation fluid for carbon source detection of methanol fuel.

5. The application according to claim 4, characterized in that, The carbon source detection includes: mixing the methanol fuel to be tested and the methanol quenching and suppression scintillation liquid evenly in a detection bottle, allowing it to stand and react, and then performing scintillation counting after cooling and equilibrium.

6. The application according to claim 5, characterized in that, The coincidence time window for the flicker count is set to 8~12ns, and a delay of 20ns is set to enable it.

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