A method for determining the content of Pu in foodstuffs based on inductively coupled plasma mass spectrometry 239 A method for determining the content of Pu in foodstuffs based on inductively coupled plasma mass spectrometry

Abstract

The application relates to the field of element content determination, in particular to a method for determining Pu content in food based on inductively coupled plasma mass spectrometry. 239 The method comprises the following steps: after a food sample to be detected is weighed, the food sample is frozen and dried, crushed, anhydrous sodium carbonate is added to perform a saponification reaction; the food sample to be detected is subjected to ashing treatment to obtain sample ash; reverse aqua regia and a shielding agent are added to the sample ash to perform a digestion reaction; the solution after digestion is loaded onto a TK200 resin column in two stages in series to perform separation and purification, and a detection solution is obtained; and the Pu content in the detection solution is detected by inductively coupled plasma mass spectrometry equipped with a collision / reaction cell. 239 The application has higher precision, accuracy and sensitivity when detecting ultra-trace Pu in food, and can complete the accurate measurement of radioactivity 239 Pu in a short time. 239 The application is an ideal method for rapidly detecting Pu in food. 239 The application is an ideal method for rapidly detecting Pu in food.

Description

Technical Field

[0001] This invention relates to the field of elemental content determination, and more particularly to a method for determining the content of elements in food based on inductively coupled plasma mass spectrometry. 239 Methods for determining Pu content. Background Technology

[0002] Plutonium-239 ( 239 Pu, half-life T 1 / 2 = 24110 y) is one of the most important transuranium (U) elements. It is a man-made radionuclide that is commonly produced in human nuclear activities and can therefore enter the ecosystem through nuclear accident emissions and global deposition. 239 Pu is the most important isotope of Pu, and due to its high chemical toxicity and long-term persistence in the environment, it is considered one of the most toxic radioactive substances. 239 Pu can enter plants through root absorption or surface adsorption, and accumulates in animals and humans through the food chain. After dietary intake, 239 Pu (Polyurethane) tends to accumulate in the liver and bones, causing cell damage and chromosomal aberrations, potentially increasing the incidence of cancer. Given... 239 Pu has significant radiotoxicity and carcinogenic risks, and is used for monitoring food. 239 Pu content is of great significance for protecting human health.

[0003] Currently, due to food 239 The content of Pu is usually at trace levels (0.06 ~ 3.38 mBq / kg·wet), and accurate detection of it is crucial. 239 The content of Pu is challenging. Currently, detecting it in food... 239 Pu (pure energy) samples typically undergo ashing, chemical separation, and source preparation via electrodeposition, followed by measurement using an alpha spectrometer. However, the alpha spectrometer measurement process is complex and time-consuming, often requiring several days or even a week. Furthermore, due to… 239 Pu and 240 The energies of the alpha radiators of Pu are very close, at 5.15 MeV and 5.16 MeV respectively, making them difficult to distinguish using an alpha spectrometer. Therefore, only measurements of... 239+240 Total activity of Pu. Furthermore, both alpha spectrometers and low-background alpha meters measure radioactivity counts; insufficient measurement time can lead to poor accuracy. Moreover, the number of samples that can be measured in a single alpha spectrum analysis is very limited; when dealing with batches of samples, multiple measurements are necessary, which means… 239 Both the time and economic costs of Pu testing are relatively high.

[0004] Inductively coupled plasma mass spectrometry (ICP-MS) has a much higher sensitivity (μBq / kg) than alpha spectroscopy (mBq / kg), and offers advantages such as a wide linear range, rapid detection, high resolution, and the ability to simultaneously detect large numbers of samples, overcoming the inherent limitations of alpha spectroscopy. In recent years, ICP-MS technology has made significant progress in the analysis and detection of Pu isotopes in environmental and human biological samples, such as soil, water, and urine. However, due to the diverse types and complex matrices of food samples, especially the high phosphorus (P) content in food matrices, which forms H3PO4 and HPO4 in acidic media, ICP-MS remains challenging. 2- These phosphate compounds can form strong complexes with phosphorus (P) to form precipitates, thus reducing the recovery rate of Pu. Furthermore, in food samples... 239 Pu content is extremely low, requiring enrichment with large sample sizes (kilogram-level). However, animal-based foods have high fat content, which easily expands and overflows during the carbonization stage at 200–350 °C, producing dense white smoke. This leads to reduced Pu recovery and increased risk of cross-contamination, placing extremely high demands on sample processing. Furthermore, when using ICP-MS for detection, the mass number and... 239 Pu is a homogeneous uranium hydride ion that is exactly the same as Pu ( 238 UH + ) will be to 239 The measurement of Pu is greatly interfered with. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the content of certain substances in food based on inductively coupled plasma mass spectrometry. 239 A method for determining the Pu content is used to solve the aforementioned technical problems.

[0006] To achieve the above objectives, this invention provides a method for determining the content of certain substances in food based on inductively coupled plasma mass spectrometry. 239 A method for determining Pu content, the method comprising:

[0007] After weighing the food sample to be tested, freeze-drying and pulverizing it, anhydrous sodium carbonate is added to carry out a saponification reaction.

[0008] The food sample to be tested is ashed to obtain sample ash;

[0009] Anti-aqua regia and a masking agent were added to the sample ash to carry out a digestion reaction;

[0010] The digested solution was loaded onto a two-stage series-connected TK200 resin column for separation and purification to obtain the test solution.

[0011] The sample solution was analyzed by inductively coupled plasma mass spectrometry equipped with a collision / reaction cell. 239The Pu content was tested.

[0012] The technical effects and advantages of this invention are as follows:

[0013] This invention involves adding an appropriate amount of anhydrous sodium carbonate to the food sample before ashing to induce a saponification reaction, converting the oils in the food sample into stearic acid, thereby effectively improving the ashing efficiency of animal-based foods and reducing losses. Furthermore, by using a masking agent, such as a ferric ion solution (e.g., FeCl3), as a masking agent for phosphorus (P), the large amount of phosphorus in the food matrix is ​​eliminated. 239 The interference from uranium (Pu) further improved the accuracy of the method. To remove interfering components such as uranium, a two-stage TK200 resin column was coupled with the kinetic energy discrimination (KED) mode of ICP-MS, achieving a total decontamination factor of 3.53 × 10⁻⁶ for uranium. 12 Therefore, this invention is used to detect trace amounts of [unspecified substance] in food. 239 When using Pu, it has higher precision, accuracy and sensitivity.

[0014] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the 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 based on these drawings without creative effort.

[0016] Figure 1 This invention provides an embodiment for determining the content of certain substances in food based on inductively coupled plasma mass spectrometry. 239 Flowchart of the method for determining Pu content;

[0017] Figure 2 The graph shows the retention performance of TK200 resin column for Pu(Ⅳ) and U(Ⅳ) under different acidity conditions in an embodiment of the present invention.

[0018] Figure 3 This is a graph showing the loss rate of Pu(IV) during secondary rinsing with different concentrations of HNO3 in embodiments of the present invention.

[0019] Figure 4 Different eluents in the embodiments of the present invention 239 Pu elution and its components 239 Pu residual amount diagram;

[0020] Figure 5 The elution reagent containing the reducing agent NH2OH·HCl in the embodiments of the present invention is used for... 239Graph showing the elution effect and eluent consumption of PU;

[0021] Figure 6 Different He flow rates and concentrations are used in embodiments of the present invention. 238 Contribution of U to signal strength at m / z=239. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0024] This invention provides a method for determining the content of certain substances in food based on inductively coupled plasma mass spectrometry. 239 Methods for determining Pu content, such as Figure 1 As shown, the method includes:

[0025] 1. Weigh the food sample to be tested, freeze-dry it, pulverize it, and add anhydrous sodium carbonate to carry out a saponification reaction;

[0026] The mass ratio of anhydrous sodium carbonate to the food sample to be tested is 1:800-1200, preferably 1:1000, for example, 1 g of anhydrous sodium carbonate is added per kilogram of fresh sample.

[0027] 2. Ash the food sample to be tested to obtain sample ash.

[0028] The ashing treatment conditions include: heating from room temperature to a first temperature, carbonizing at the first temperature, further heating to a second temperature, and ashing at the second temperature. Specifically, the first temperature is 220-270 °C, preferably 230, 240, 250, and 260 °C; the second temperature is 430-470 °C, preferably 440, 450, and 460 °C; the carbonization time is 2.5-3.5 hours, preferably 3 hours; the ashing time is 10-26 hours, preferably 12-24 hours, more preferably 10, 12, 15, 18, and 20 hours; and the time to heat to the first temperature and the time to heat to the second temperature are both 0.3-0.7 hours, preferably 0.4, 0.5, and 0.6 hours.

[0029] 3. Add anti-aqua regia and masking agent to the sample ash to carry out a digestion reaction.

[0030] The masking agent includes at least one of the following: aluminum nitrate and ferric chloride. Of course, other substances that can shield phosphorus can also be used.

[0031] The ratio of sample ash to anti-aqua regia is 1 g: 8 ml-12 ml; the mass ratio of sample ash to masking agent is 1:0.8-1.2. Preferably, the ratio of sample ash, anti-aqua regia, and FeCl3 is 1 gram of sample ash to 10 ml of anti-aqua regia and 1 gram of ferric chloride.

[0032] 4. Load the digested solution onto a two-stage TK200 resin column connected in series for separation and purification to obtain the test solution.

[0033] Specifically, the process includes: pretreating the first and second TK200 resin columns with acid; loading the digested solution onto the first TK200 resin column and eluting it twice with HNO3 of different concentrations; adding eluent to the first TK200 resin column for initial elution, loading the initial eluted solution onto the second TK200 resin column, and performing a second elution with the same eluent to obtain a second eluted solution; and mixing the initial eluted solution and the second eluted solution to obtain the test solution.

[0034] The TK200 resin is designated as (10×2 mL, 50-100 μm particle size).

[0035] The concentration of HNO3 in the digested solution is 2-10 M, preferably 4, 5, 6, and 8 M; the first elution solution is 2-10 M HNO3, preferably 4, 5, 6, and 8 M HNO3; the second elution solution is 2-6 M HNO3, preferably 3, 4, and 5 M HNO3; the eluent is a mixture of 0.001-0.05 M HF, 0.01-0.2 M NH2OH·HCl, and 0.01-0.2 M HCl, preferably a mixture of 0.005-0.03 M HF, 0.05-0.15 M NH2OH·HCl, and 0.05-0.15 M HCl, more preferably a mixture of 0.01 M HF, 0.1 M NH2OH·HCl, and 0.1 M HCl.

[0036] The acid solution used for pretreatment of the first TK200 resin column is the same as the initial elution solution; the acid solution used for pretreatment of the second TK200 resin column is the same as the elution solution.

[0037] 5. The sample solution was analyzed by inductively coupled plasma mass spectrometry equipped with a collision / reaction cell. 239 The Pu content was tested.

[0038] Specifically, ICP-MS equipped with collision / reaction cell technology (CCT) is used to detect foodborne pathogens through kinetic energy discrimination mode (KED). 239 High-precision detection of Pu.

[0039] Wherein, the collision gas in the collision / reaction tank is He, and the flow rate of He is 4.5 mL / min-6.5 mL / min; 239 Pu content ≥ 3.6 fg / g sample ash.

[0040] To better understand this solution, the following embodiments are also provided.

[0041] A method for determining the content of certain substances in food based on inductively coupled plasma mass spectrometry 239 The method for determining Pu content involves the following specific steps:

[0042] 1. Food sample pretreatment and ashing

[0043] After weighing the edible portion, freeze-dry and pulverize it. Add 1 g of anhydrous sodium carbonate per kilogram of fresh sample, then place the food sample in a muffle furnace and ashing it according to the procedure shown in Table 1. Next, take 10 g of sample ash and digest it with 100 mL of anti-aqua regia (HNO3:HCl = 3:1, v / v) at 200 ℃ for 3 h, adding 10 g of FeCl3 during digestion. Figure 2After sample digestion, the sample was filtered, the filtrate was collected, and the residue was washed with 8 M HNO3. The filtrate and washings were combined, and then 8 M HNO3 was added to 100 mL. Subsequently, 2 g NaNO2 was added to the sample solution at room temperature to adjust the other valence states of Pu to Pu(Ⅳ) for subsequent separation and purification.

[0044] The reason for adding FeCl3 is as follows: During the subsequent separation and purification of Pu(IV), Pu(IV) dissolves in 8M HNO3 and reacts with NO3. – Coordination forms an ionic complex [Pu(NO3)] n ] 4–n (n=1~6), these complexes are adsorbed onto the resin, thus achieving the retention of Pu(IV) on the resin column. Meanwhile, under acidic conditions, P in food will react as HPO4. 2- H2PO4 1- It exists in the form of H3PO4, while HPO4 2- and H2PO4 1- It can coordinate with Pu(IV) to form a precipitate, which will cause 239 The loss of Pu. Furthermore, the H3PO4 molecule has a stronger coordination ability with Pu(IV) than NO3. – It readily forms a more stable complex [Pu(H3PO4)] 4+ This hinders the adsorption of Pu(IV) on the resin column. However, under acidic conditions, iron ions can remain stable and react with HPO4. 2- H2PO4 1- It undergoes a strong coordination reaction with H3PO4. Therefore, adding an appropriate amount of FeCl3 during digestion masks the interference of P in the food sample, thereby improving... 239 Pu recovery rate.

[0045] Table 1 Food Sample Ashing Procedure

[0046]

[0047] 2. 239 Pu separation and enrichment

[0048] ICP-MS in detection 239 Pu faces challenges such as matrix interference, polyatomic ion interference, and peak tailing. Among these, the most noteworthy is the interference from uranium hydrogen ions (PH). 238 UH + ) for target ions 239 Pu + Isotopic interference. Studies have shown that food samples contain... 238 U content ratio 239 Pu is more than four orders of magnitude higher. Furthermore, during ICP-MS measurements…238 UH + The formation rate is approximately 10 -3 ( 238 UH + / 238 U + This will interfere with the food's... 239 Accurate quantification of Pu. Therefore, enrichment of food samples. 239 Pu and effectively eliminate 238 U and 238 UH + Interference 239 Accurate quantification of Pu is crucial.

[0049] This invention uses two-stage tandem TK200 resin columns to separate and purify food samples. 239 The process involves the following steps: First, the sample solution containing Pu(Ⅳ) is loaded onto the first TK200 resin column (pretreated with 10 mL of 8 M HNO3 solution). Then, it is eluted sequentially with 10 mL of 8 M HNO3 and 40 mL of 3 M HNO3, followed by elution with 20 mL of 0.01 M HF-0.1 M NH2OH·HCl-0.1 M HCl solution. The eluent is then loaded directly onto the second TK200 resin column (pretreated with 10 mL of 0.01 M HF-0.1 M NH2OH·HCl-0.1 M HCl solution) and eluted with 20 mL of 0.01 M HF-0.1 M NH2OH·HCl-0.1 M HCl solution. The eluents from the first and second columns are combined, evaporated to dryness at 200 °C, and then dissolved in 5 mL of concentrated HNO3. The solution was evaporated to dryness again at 200 °C, and the residue was dissolved in 10 mL of 1% HNO3 (v / v) for analysis. The optimization measures for this step are described in detail below:

[0050] 2.1 Optimization of sample loading solution

[0051] While reducing Pu to Pu(Ⅳ), U may also be reduced to U(Ⅳ). TK200 resin exhibits good retention capacity for both Pu(Ⅳ) and U(Ⅳ) in HNO3 medium. However, the acidity of the sample solution affects the retention effect of TK200 resin on Pu(Ⅳ) and U(Ⅳ). Therefore, to maximize the retention capacity of Pu(Ⅳ) while simultaneously reducing the retention rate of U(Ⅳ), this invention investigated the retention performance of TK200 resin columns on Pu(Ⅳ) and U(Ⅳ) under different acidity conditions. The results are as follows: Figure 2 As shown.

[0052] according to Figure 2It can be seen that when the HNO3 concentration is in the range of 2-10 M, the TK200 resin column maintains a high retention rate (>86%) for both Pu(Ⅳ) and U(Ⅳ). This is attributed to the high partition coefficients of Pu(Ⅳ) and U(Ⅳ) on the TK200 resin in media with HNO3 concentrations greater than 0.2 M. Furthermore, from... Figure 2 It can be observed that the retention rate of Pu(Ⅳ) did not change significantly under different HNO3 concentrations, while the retention rate of U(Ⅳ) gradually decreased with increasing HNO3 concentration, which is consistent with previous research results. Notably, when the HNO3 concentration in the sample solution was 8 M, the retention rate of Pu(Ⅳ) reached its highest value (98.4%), while the retention rate of U(Ⅳ) dropped to its lowest (86%). At this point, the difference between the retention rates of Pu(Ⅳ) and U(Ⅳ) was the largest, with a retention rate ratio of 1.13. Therefore, this scheme preferably sets the HNO3 concentration of the sample solution to 8 M.

[0053] 2.2 Optimization of Eluent

[0054] After the sample is loaded onto the column, the TK200 resin adsorbs both Pu(IV) and impurities. Therefore, during the rinsing process, it is necessary to remove impurities as much as possible while ensuring strong Pu(IV) adsorption. The choice of rinsing solution is a key factor affecting the recovery rate; it must effectively remove impurities while maximizing the retention of Pu(IV), thereby improving the accuracy and sensitivity of the detection. Therefore, this method employs a two-step rinsing approach: First, the TK200 resin is rinsed with HNO3 of the same concentration as the loading solution to maintain a stable Pu(IV) adsorption state and prevent Pu(IV) loss due to acidity changes; then, a second rinsing with HNO3 of a different concentration is performed to remove impurities.

[0055] This invention investigated the loss rate of Pu(IV) during secondary rinsing with different concentrations of HNO3 (2 M, 3 M, 4 M, 5 M, and 6 M). The results showed that when the HNO3 concentration was in the range of 2-6 M, the loss of Pu(IV) did not change significantly and was consistently below 10%. Figure 3 As shown. Furthermore, previous studies have shown that various interfering elements such as Hg, Pb, and Tl can be effectively removed in 3 M HNO3 medium. Therefore, this scheme preferably uses 3 M HNO3 as the second-step eluent.

[0056] 2.3 Selection of Elution Buffer

[0057] The retention capacity of TK200 resin for Pu(IV) and U(IV) is closely related to the type and concentration of acid. In 4-9 M HCl and 0.1-8 M HNO3 solutions, the resin exhibits extremely strong retention capacity for Pu(IV); however, in HCl solutions below 4 M, the retention capacity is relatively weak, and the retention effect worsens with lower acidity. Notably, the resin demonstrates extremely strong retention capacity for U(IV) in both 0-10 M HCl and 0-10 M HNO3 solutions. Based on this characteristic, using low-concentration HCl solution as the eluent may achieve efficient separation of Pu(IV) and U(IV).

[0058] The elution effect of different concentrations of HCl on Pu(IV) and U(IV) was investigated. It was found that when using 4 M HCl, only a small amount of Pu(IV) was eluted (<20%). Even at a HCl concentration as low as 0.1 M, a large amount of Pu(IV) remained uneluted, with a recovery rate of only 32.6%, indicating that a single low-concentration HCl solution cannot achieve complete elution of Pu(IV). Considering that TK200 resin has a strong adsorption capacity for Pu(IV) but a weak adsorption capacity for Pu(III), a reducing agent NH2OH·HCl was added to the eluent to reduce Pu(IV) to Pu(III), and HF was added synergistically to enhance the elution capacity. The results showed that after adding 0.1 M NH2OH·HCl to 0.1 M HCl, the Pu(IV) recovery rate reached over 90%; further addition of HF increased the recovery rate to over 95%. Figure 4 As shown. Among them, Figure 4 In the eluent types, A represents 4 M HCl, B represents 0.1 M HCl, C represents 0.1 M NH2OH·HCl-0.1 M HCl, D represents 0.1 M HF-0.1 M HCl-0.1 M NH2OH·HCl; and E represents 0.01 M HF-0.1 M HCl-0.1 M NH2OH·HCl.

[0059] In addition, the elution curve ( Figure 5 The results show that 0.01 M HF-0.1 M HCl-0.1 M NH2OH·HCl and 0.1 M HF-0.1 M HCl-0.1 M NH2OH·HCl can elute Pu(IV) earlier than 0.1 M HCl-0.1 M NH2OH·HCl solution, and only 20 mL is needed to elute the vast majority of plutonium Pu(IV) (>95%). However, at higher HF concentrations (0.1 M), although Pu(IV) can be eluted sufficiently, the amount of uranium eluted is much higher than with other eluents. When the added HF concentration is 0.01 M, the uranium elution rate is not significantly different from that without HF. Figure 4 Therefore, this scheme preferably uses 0.01 M HF-0.1 M HCl-0.1 M NH2OH·HCl as the eluent.

[0060] 3. 239 Pu determination

[0061] This study employed a separation and purification scheme using dual TK200 resin columns in series, achieving... 238 U is efficiently removed. However, the two-column system still cannot completely remove it. 238 U, residual trace amount 238 U can interfere with the measurement.

[0062] remove 238 UH + In addition to its contribution to the peak intensity at m / z=239, 238 The single-atom tailing peak of U may also affect this mass-to-charge ratio signal. Since the peak tail contribution at m-1 is typically higher than that at m+1, a conservative estimate can be made by monitoring the signal at m / z=237. 238 The peak tail contribution of U at m / z=239. Experimental determination of 10 ng / mL 238 The U standard solution showed an extremely weak signal at m / z=237, close to the process blank value, indicating... 238 The peak tail contribution of U at m / z=239 is negligible. Therefore, ICP-MS determination... 239 The main sources of interference during Pu are 238 UH + For trace amounts 238 UH + To address the interference problem, this solution employs ICP-MS equipped with collision / reaction cell technology (CCT) and utilizes kinetic energy discrimination mode (KED) to achieve the detection of food interference. 239 High-precision detection of Pu. This technology effectively suppresses... 238 UH + Multi-atom interference significantly improves the selectivity of the method.

[0063] In kinetic energy discrimination (KED) mode, the colliding gas He effectively eliminates [the interference of] specific kinetic energy-disrupting ions by selectively blocking them. 238 UH + Interference. This method investigates the effects of different He flow rates and concentrations. 238 The contribution of U to the signal strength at m / z=239, such as Figure 6 As shown. In standard mode (STD, no gas is introduced), even 238 Even at concentrations as low as 0.01 ng / mL, the signal response at m / z = 239 (>10 cps) still significantly interferes with the signal. 239The determination of Pu. It is noteworthy that introducing the KED mode of He can effectively suppress this type of interference. When 238 When the U concentration is below 0.1 ng / mL and the He flow rate is 6.5 mL / min, 238 UH + The signal was significantly reduced, contributing less than 0.1 cps to the m / z=239 signal. However, subsequent experiments showed that as the He flow rate increased, 239 The signal intensity of the Pu standard solution decreased synchronously, indicating that the introduction of He weakens the detection sensitivity of the target ion. Therefore, considering all factors... 239 Pu detection sensitivity and 238 UH + For optimal removal efficiency, this protocol recommends a He flow rate of 5.5 mL / min. Under these conditions, 0.1 ng / mL 238 The test results of the U standard solution showed that 238 UH + The count was less than 1 cps, confirming that the interference was effectively suppressed.

[0064] The uranium decontamination factor of food samples purified by two-stage TK200 resin column separation can reach 4.1 × 10⁻⁶. 7 In ICP-MS measurements, using KED mode and adjusting the collision gas (He) flow rate to 5.5 mL / min effectively eliminates residual U generation. 238 UH + right 239 Pu + Interference, 238 UH + / 238 U + The ratio is 1.16 × 10 -5 Chemical separation using two tandem TK200 resin columns, 238 The overall detergency factor for U interference reached 3.53×10. 12 This allows for the detection of trace amounts of uranium from food environments containing high concentrations (162.1 mg / kg). 239 Precise measurement of Pu.

[0065] It should be noted that the specific operating conditions for ICP-MS are shown in Table 2. 1% HNO3 (v / v) was used as the cleaning solution, and the concentration was 0.1 pg / mL. 209 Bi is used as an internal standard.

[0066] Table 2. Specific Operating Conditions of ICP-MS

[0067]

[0068] The following are the validation parameters for the sensitivity, accuracy, recovery rate, and repeatability of this protocol:

[0069] 1. Detection limit and linearity

[0070] 1.1 Preparation of Standard Solutions

[0071] Transfer an appropriate amount 239 The Pu standard solution was placed in a 10 mL volumetric flask and diluted to the mark with 1% nitric acid (v / v) to prepare a standard stock solution with a concentration of 1 ng / mL. This stock solution was stored at 4 °C. 1.0 mL of the standard stock solution was placed in a 100 mL volumetric flask and diluted to the mark with 1% nitric acid (v / v). The solution was shaken well to obtain a standard working solution with a concentration of 10 pg / mL. This working solution was stored at 4 °C. Before use, the standard working solution was diluted with 1% nitric acid (v / v) to prepare calibration solutions with concentrations of 0.1, 0.5, 1.0, 2.0, and 5.0 pg / mL.

[0072] 1.2. Evaluation was conducted by plotting a calibration curve (excluding the matrix) containing five concentration levels. 239 The linear relationship of Pu. A process blank sample was prepared using the same method as the actual analytical sample, and the results were analyzed. 239 The limit of detection (LOD) for Pu is calculated by multiplying the detection sensitivity by three standard deviations of the process blank measurement results (n=10) (Formula 1).

[0073] (1)

[0074] Where: S: Standard deviation of blank measurement (cps); V: Volume before analysis (mL); SI: Instrument tolerance 239 Pu sensitivity (cps / (ng / mL)); γ: method recovery (%); m: food sample mass (g).

[0075] 1.3. Within the concentration range of 0.1–5.0 pg / mL, the correlation coefficient (r) of the calibration curve exceeds 0.999, indicating good linearity. The linear equation is y = 178x (where y is...). 239 Pu count value, x is 239 (Pu concentration). 239 The difference between the calibration value and the nominal value of Pu is within ±10%. The limit of detection (LOD) for ash samples is 3.6 fg / g (ash content), which is applicable to various fresh food samples. 239 The detection limit of Pu can be calculated based on the measured gray-to-freshness ratio.

[0076] 2. Recovery rate and repeatability

[0077] The accuracy and precision of this invention were evaluated using a spiked recovery experimental system: representative food ash samples (fish, shrimp, crab, algae, and chicken) were selected, and three concentration levels of spiked recovery were added: low (0.120 pg), medium (0.367 pg), and high (0.561 pg). 239 Pu standard solution. The recovery rate was evaluated by calculating the ratio of the average detected concentration to the theoretical concentration of the spiked sample. Multiple analyses were performed on spiked samples at each spiking level (n=4), and the repeatability of the method was evaluated by calculating the relative standard deviation. The experimental results are shown in Table 3.

[0078] Table 3. Recovery and Repeatability Experiment Data

[0079]

[0080] According to Table 3. 239 The spiked recoveries of Pu ranged from 54.9% to 83.7%, with an average recovery of 74% and relative standard deviations (RSD) ranging from 1.4% to 6.6%, indicating that this quantitative analytical method has good recovery and repeatability.

[0081] In summary, after separation and purification using a two-stage TK200 resin column, the sample contained... 238 U has a detergency factor (DF) of 4.1 × 10⁻⁶. 7 When performing ICP-MS analysis, the KED mode was used and the collision gas (He) flow rate was adjusted to 5.5 mL / min, which effectively eliminated the generation of residual U. 238 UH + right 239 Pu + Interference ( 238 UH + / 238 U + The ratio dropped to 1.16 × 10 -5 Combining chemical separation with a two-column tandem configuration, for 238 The overall DF of U-interference has been increased to 3.53 × 10⁻⁶. 12 Theoretically, high performance can be achieved. 238 U content (162.1 mg / kg) in food trace amounts 239 Accurate quantification of Pu was achieved. Furthermore, it exhibited good linearity within the detection concentration range (correlation coefficient r > 0.999), a limit of detection (LOD) of 3.6 fg / g in the ash matrix, an average recovery rate exceeding 74%, and a relative standard deviation below 6.6%. This was demonstrated through analysis of actual food samples. 239 Quantitative analysis of Pu validated the applicability of the method, demonstrating its rapid, accurate, and sensitive characteristics, making it suitable for use in food analysis. 239 An ideal method for Pu detection. Compared to traditional alpha spectrometer measurements, this method can complete radioactivity detection in a shorter time.239 Accurate Pu measurements allow for a turnaround time of less than three days for fresh food sample analysis, while alpha spectrometer measurements typically require more than a week.

[0082] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the content of Pu in foodstuffs based on inductively coupled plasma mass spectrometry, characterized in that, 239 Pu is determined by means of the isotope 239Pu. The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The Pu content is detected by inductively coupled plasma mass spectrometry on the liquid to be tested equipped with a collision / reaction cell 239 cell. The method comprises: The method comprises: The method comprises: The method comprises: The method comprises:

2. The method of claim 1, wherein, The method comprises:

3. The method of claim 1, wherein, The method comprises:

4. The method of claim 3, wherein, The method comprises:

5. The method of claim 1, wherein, The method comprises:

6. The method of claim 5, wherein, The method comprises:

7. The method of claim 1, wherein, The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises: The method comprises:

8. The method of claim 1, wherein, The 239 Pu content > 3.6 fg / g sample ash.

Images