A method for rapid preparation and testing of strontium isotopes in wine

Abstract

The present invention provides a method for rapidly preparing and testing strontium isotopes in wine. The method uses hydrofluoric acid co-precipitation to capture Sr in wine, separates and purifies it to obtain a Sr-Ca-Mg fluoride co-precipitate sample; the prepared sample is then diluted and spotted on a high-purity Re filament, and Sr isotopes are tested using thermal ionization mass spectrometry. The method of the present invention uses hydrofluoric acid co-precipitation technology to directly eliminate more than 85% of the matrix elements in wine, while also eliminating the main isotopes. 87 Rb interference; it can separate strontium isotopes in wine without traditional resin chromatography column purification technology, and directly test the strontium isotope ratio in wine by spotting, which improves the preparation efficiency by more than 2 times, reduces the preparation cost by at least 95%, and can greatly reduce the emission of chemical hazardous waste reagents. The method is simple to operate, low-cost, fast, effective, green and environmentally friendly, and has broad application prospects for the traceability of the origin of wine and alcoholic foods.

Description

Technical Field

[0001] The present invention relates to the technical field of wine detection and analysis, and in particular to a method for testing strontium isotopes in wine, and more particularly to a method for rapidly preparing and testing strontium isotopes in wine. Background Art

[0002] The practice of passing off inferior wine as superior is widespread, especially in the high-end red wine market. Therefore, it is urgent and necessary to accurately trace the origin of high-end wines and establish corresponding identification indicators. These specific physical and chemical indicators can effectively identify the quality and origin of wines.

[0003] Common origin identification technologies mainly include organic component fingerprint technology, infrared spectroscopy fingerprint technology, mineral element chemical fingerprint technology and isotope fingerprint technology. Among them, mineral element combined with isotope fingerprint identification technology has the most extensive application in origin identification, and its origin identification accuracy can be better than 90%. Therefore, it is widely favored by food scientists. Among the many isotope (O, H, B, Li, Sr, Pb) identification fingerprint technologies, the use of Sr isotope for red wine origin identification has a wider range of successful applications because 87 Sr / 86 The Sr isotope ratio is basically not affected by the physical and chemical processes in the later winemaking process, and is generally only affected by the soil, water source, environment, and climate inherent in the wine production area. Therefore, the Sr isotope combined with the mineral element map can more accurately reflect the origin characteristics of geographically indicated foods. Generally speaking, for food origin traceability research, 87 Sr / 86 The accuracy of the Sr isotope ratio must be better than 0.003% (2RSE).

[0004] Currently, there are multiple technologies used to test Sr isotopes in wine samples, such as inductively coupled plasma mass spectrometry (ICP-MS), multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), and thermal ionization mass spectrometry (TIMS). Among the various analytical techniques developed above, TIMS offers significant advantages, including high sensitivity, low memory effect, high accuracy, and high analytical precision. Therefore, TIMS has long been considered by analytical chemists and geochemists as the benchmark test technology for Sr isotope analysis. There are two main factors that affect TIMS testing:

[0005] ① 87 Rb and 87 Sr is an isobaric isotope. Therefore, when mass spectrometry is performed 87 Rb will seriously interfere 87 Sr, resulting in the final test 87 Sr / 86The Sr ratio is significantly higher, which seriously affects the final test accuracy, especially for 87 Sr / 86 The accuracy of the Sr ratio test generally needs to be better than 0.003% (2RSE) to meet the requirements of food origin traceability.

[0006] ②The main matrix elements in food samples such as K, Na, Ca, and Mg will significantly inhibit the ionization efficiency of Sr, resulting in a serious reduction in test sensitivity, thereby affecting the test accuracy.

[0007] Therefore, in order to eliminate the 87 Rb pair 87 Sr will cause strong interference, and the influence of matrix elements on Sr ionization. Traditional methods generally require the use of strong cationic resin or Sr special resin ion exchange technology to remove matrix elements, and at the same time separate high-purity Sr components, and then use thermal ionization mass spectrometry (TIMS) to test 87 Sr / 86 Sr.

[0008] Although the above-mentioned traditional TIMS analysis scheme has extremely high accuracy and test precision, the traditional TIMS test scheme is time-consuming and labor-intensive, and the experimental cost is high, which is specifically manifested in the following aspects:

[0009] (1) Purification of samples requires the use of expensive imported Sr-specific resins or cationic resins, which have high preparation costs.

[0010] (2) The preparation process is relatively cumbersome, and the tedious operation steps (such as pre-cleaning of the chromatographic column, multi-step reagent extraction and cleaning, and evaporation of the enriched components) will consume a lot of manpower. The above separation process generally requires at least one working day to obtain a concentrated Sr sample, which greatly restricts the laboratory's working capacity.

[0011] (3) The process of separating Sr by ion exchange chromatography will produce a large amount of hydrochloric acid or nitric acid waste liquid, which is very unfriendly to the environment. The subsequent treatment of the waste liquid also requires special fees.

[0012] In summary, while conventional ion exchange resin purification techniques for Sr in wine samples offer good separation results, they suffer from low efficiency and high costs, necessitating urgent improvements. To date, no convenient and efficient preparation method suitable for TIMS analysis of Sr isotopes in wine samples has been developed. Therefore, improved TIMS techniques for analyzing Sr isotopes in wine samples, while maintaining the same analytical precision and accuracy as conventional TIMS, are urgently needed. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide a method for rapidly preparing and testing strontium isotopes in wine. The method is applicable to the testing of Sr isotopes in conventional wine samples and can rapidly obtain Sr isotope samples suitable for TIMS testing. The method is simple to operate, has high separation efficiency, low analysis cost, and is environmentally friendly.

[0014] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0015] The present invention provides a method for rapidly preparing and testing strontium isotopes in wine, comprising the following steps:

[0016] S1. Co-precipitation to obtain Sr sample: Sr in wine was captured by hydrofluoric acid co-precipitation, and then separated and purified to obtain Sr-Ca-Mg fluoride co-precipitation sample;

[0017] S2. Thermal ionization mass spectrometry for Sr isotope testing: The sample obtained in step S1 is applied to a high-purity Re filament to complete Sr isotope testing and analysis.

[0018] Furthermore, step S1 is specifically as follows:

[0019] S101, wine sample digestion: evaporate an appropriate amount of wine sample to dryness, then add preset amounts of concentrated nitric acid and hydrogen peroxide in portions to digest the sample to obtain wine residues free of organic matter;

[0020] S102. Separate and purify the strontium sample by co-precipitation: dissolve the wine residue with an appropriate amount of dilute hydrochloric acid, add a predetermined amount of hydrofluoric acid, and heat the mixture under closed conditions to obtain a fluoride co-precipitation sample rich in Sr-Ca-Mg;

[0021] S103. Prepare a strontium sample solution: add a preset amount of nitric acid to dissolve the Sr-Ca-Mg fluoride co-precipitation sample to obtain a strontium sample solution for later use.

[0022] In the present invention, since TIMS has extremely high sensitivity in measuring Sr, high-precision testing of a 0.2 ng Sr sample can be easily achieved. Therefore, the obtained Ca-Mg-Sr fluoride precipitate can be further diluted after dissolution to further reduce the interference effect of residual matrix elements, thereby obtaining high-precision Sr isotope data.

[0023] Furthermore, step S1 further includes the steps of:

[0024] According to the crude concentration results of Sr measured by ICP-MS, the actual weight of Sr obtained by co-precipitation was calculated based on the sample weight and co-precipitation recovery rate to determine the sample spotting amount.

[0025] The amount of the Sr sample spotted in the present invention is 1.4 to 35 ng, preferably 4 to 6 ng.

[0026] Furthermore, the wine sample digestion process in step S101 is specifically as follows:

[0027] Weigh an appropriate amount of wine sample and evaporate it at 80-90°C until it is completely dry; then, add 14 mol / L concentrated nitric acid and 30% hydrogen peroxide in portions to digest the wine sample, the volume ratio of the total volume of the added concentrated nitric acid and hydrogen peroxide to the volume of the wine sample being 3:1, and the amount of hydrogen peroxide used is 1 / 8 of the volume of the concentrated nitric acid; specifically, first add all the hydrogen peroxide and an appropriate amount of concentrated nitric acid, and nitrate the wine at 80-90°C, the volume ratio of the concentrated nitric acid to the hydrogen peroxide added this time being 3:1; then, when it is evaporated to a black colloidal paste, add the remaining concentrated nitric acid, keep it warm at 150-160°C under sealed conditions for 4-6 hours, and evaporate the sample to dryness at 150-160°C after unsealing to obtain the digested wine residue.

[0028] Generally, 3 mL of wine sample is taken and evaporated to dryness at low temperature, and then 3 mL of 14 mol / L concentrated nitric acid and 1 mL of 30% hydrogen peroxide are added to digest the wine sample; then, when the wine sample is evaporated to a black colloidal paste, the remaining 5 mL of concentrated nitric acid is added. In order to avoid splashing of the solution, the remaining concentrated nitric acid can be added again in batches, such as adding 2 mL of concentrated nitric acid first, evaporating it to dryness at 80-90°C, and then adding the remaining 3 mL of concentrated nitric acid. Under sealed conditions, keep it warm at 150-160°C for 4-6 hours. After unsealing, evaporate the sample at 150-160°C to dryness, and finally obtain the digested wine residue.

[0029] In the method of the present invention, adding concentrated nitric acid and hydrogen peroxide in batches to digest the wine sample can avoid adding too much at one time, which would cause a violent reaction and splashing of the solution.

[0030] Furthermore, the processes of steps S102 and S103 are specifically as follows:

[0031] S102. Add an appropriate amount of dilute hydrochloric acid to the digested wine residue to dissolve it to obtain a residue liquid, then add a preset amount of 22 mol / L hydrofluoric acid, with the volume ratio of hydrofluoric acid to the residue liquid being 2 to 3:1; and keep the mixture at 120° C. to 130° C. under sealed conditions for 1.5 to 2 hours to obtain a fluoride co-precipitation sample rich in Sr-Ca-Mg;

[0032] S103. Wait until the fluoride co-precipitate cools to room temperature, shake and centrifuge, then discard the supernatant, add a preset amount of nitric acid to the lower precipitate, shake and dissolve the sample to obtain a strontium sample solution for use.

[0033] Preferably, the concentration of the dilute hydrochloric acid used for dissolution in step S102 is 0.4 mol / L. Generally, 3 mL of wine digestion residue is dissolved with 0.5 mL of 0.4 mol / L dilute hydrochloric acid, and 1 mL of 22 mol / L hydrofluoric acid is added for co-precipitation.

[0034] Preferably, the concentration of nitric acid used to dissolve the strontium sample to prepare the strontium sample solution in step S103 is 7 mol / L. Generally, 0.3 mL of 7 mol / L nitric acid can be added to dissolve the fluoride coprecipitate obtained after coprecipitation of 3 mL of wine sample.

[0035] Furthermore, step S2 is specifically as follows:

[0036] S201, apply an appropriate amount of dilute phosphoric acid and TaF5 emitter to the surface of a high-purity Re filament and evaporate to dryness; then apply an appropriate amount of the prepared Sr sample solution to the surface of the filament and evaporate to dryness, increase the current until the filament turns dark red and hold for 4 to 6 seconds, then return the current to zero;

[0037] S202. Load the loaded filament into a thermal ionization mass spectrometer to obtain the Sr isotope results.

[0038] Preferably, the concentration of the dilute phosphoric acid in step S201 is 0.2 mol / L.

[0039] The dilute phosphoric acid in this invention acts as a binder, allowing the TaF5 emitter to be better coated and firmly fixed to the sample carrier surface. It also aids ionization, moderately enhancing the sample's ionization efficiency. Excessive phosphoric acid solution can easily damage the equipment. Generally, the sample volume for each test is 1 μL, with a maximum of 2 μL.

[0040] Preferably, the spotting volume of the TaF5 emitter and the phosphoric acid solution used in the test is 1 μL.

[0041] Preferably, the amount of the Sr sample solution spotted in step S202 is converted according to the concentration of the Sr sample solution, and is generally 0.5 to 2 μL.

[0042] Furthermore, the testing process of step S202 is specifically as follows:

[0043] S2021, evacuation of thermal ionization mass spectrometer;

[0044] S2022. Adjust the filament current to 2-2.3 amperes, the heating rate to 500 mA / min, and the corresponding ionization temperature to 1200-1300°C. Preheat at this temperature for 2-3 minutes to eliminate potential Rb interference.

[0045] S2023. Open the isolation valve and high voltage, adjust the filament current to 2.62-2.95 amperes, and the heating rate to 500 mA / min, corresponding to an ionization temperature of 1450-1520°C, and test the Sr isotope.

[0046] Furthermore, during the data collection process of testing Sr isotopes in step S2023, 88 The signal intensity of Sr is controlled at 2800~6500mV. 200 sets of data are collected under this signal intensity. 87 Sr / 86 The test accuracy of Sr is better than 0.003% (2RSE).

[0047] Furthermore, the purity of the high-purity Re filament is higher than 99.8%.

[0048] Preferably, in step S2021, the ion source is vacuumed to a vacuum better than 3×10 -7 mabr.

[0049] The basic design principle of the present invention:

[0050] In the past, when testing rock samples, some researchers also tried to use co-precipitation to separate Sr and directly test Sr isotopes. However, due to the very complex composition of the rock sample matrix (containing a large amount of Fe, Ti, Ca, Mg, K, Na) and a wide range of Rb / Sr (0.01 to 500), co-precipitation alone cannot obtain satisfactory Sr sample purity. Therefore, co-precipitation is usually not used for the preparation of Sr isotopes in conventional geological samples. Usually, co-precipitation is required in combination with traditional ion exchange resin technology to synergistically prepare Sr, and then TIMS testing is used. The main application of co-precipitation is for geological samples with high Rb / Sr ratios (such as rhyolite and mica minerals).

[0051] Compared to the complex matrix of geological samples, the matrix of digested wine samples is relatively simple. K accounts for 80–84% of the wine matrix's elemental composition by weight, while K, Na, Ca, Mg, B, and Mn contribute 99–99.4%. Furthermore, the Rb / Sr ratio in wine is relatively low, generally ranging from 1 to 2.5. Therefore, for wine samples, effectively eliminating the K-Rb interference is theoretically sufficient to ensure high-precision and accurate Sr isotope data.

[0052] To reduce analytical costs, this application scheme uses hydrogen fluoride co-precipitation to obtain an Sr sample from a wine sample. Specifically, a Ca-Mg-Sr fluoride precipitate is obtained. Although the co-precipitated sample is enriched in Sr, it also contains a relatively high concentration of matrix elements (Ca and Mg). Excessive amounts of these matrix elements can severely impact the Sr ionization efficiency, making it impossible to obtain high-precision Sr isotope data. Therefore, after co-precipitation, this method requires careful evaluation of the Sr sample loading. Excessive loading can introduce significant amounts of Ca and Mg, impacting test sensitivity, while insufficient loading can lead to rapid signal decay, making it impossible to meet the requirements of TIMS analysis.

[0053] Furthermore, while TIMS ionization temperatures for Rb and Sr differ significantly—for example, Rb's ionization temperature is 600-720°C, while Sr's is 1400-1500°C—if a small amount of Rb is present when measuring Sr isotopes, it can be eliminated by burning it off at 1300°C for 1-2 minutes to eliminate interference from the sample. However, excessive residual Rb (>30ng) cannot be eliminated by filament preheating, resulting in erroneous Sr isotope data.

[0054] To overcome the inaccuracy or even errors in Sr isotope data that may be caused by these factors, the following points are key to implementing the solution of the present invention:

[0055] 1. Optimize the Sr spot dose. Since the test object is a mixture of Ca-Mg-Sr, and the mass ratio of Ca-Mg in wine samples is usually 50 to 200 times that of Sr, if too much Sr is applied to the surface of the Re filament, a large amount of Ca-Mg impurities will also be introduced, which will seriously inhibit the ionization of Sr and fail to obtain satisfactory sensitivity and test accuracy. Therefore, a spot dose of 1.4 to 35 ng is appropriate. For ordinary wine samples, a spot dose of 3 to 6 ng is more appropriate and can meet the test of most wine samples. For wine samples with a high Ca / Sr ratio (>200), a 10 12 Ohm high impedance reception 86 Sr and 87 The Sr signal further improves the sensitivity.

[0056] 2. Optimal coprecipitation conditions. Since the Ca-Mg concentration of wine samples is generally only 30-80 ppm, and Ca and Mg are the main coprecipitants, the wine sample volume should not be too low, otherwise it will be difficult to obtain a satisfactory Sr coprecipitation recovery rate. Generally, at least 3g of sample is required.

[0057] 3. Select the most appropriate filament material. Although Re, Ta, and W can all meet high-precision analysis requirements for Rb and Sr, using Re ribbon for sample spotting has the lowest sensitivity for Rb and very high sensitivity for Sr. Considering that fluoride components still contain trace amounts of Rb, 0.2 to 2 ng of Rb will be introduced during sample spotting. Therefore, it is important to select a material that is most conducive to enhancing Sr isotope sensitivity and eliminating Rb isotope interference. Re ribbon is the optimal filament material (best for Sr sensitization, worst for Rb). Using Re ribbon as a sample carrier is more conducive to burning off Rb during the preheating process.

[0058] Beneficial effects of the present invention:

[0059] (1) Compared with the traditional ion exchange resin technology for separating Sr and combining it with TIMS technology for testing Sr isotopes, the method provided by the present invention can achieve Sr enrichment without any resin material. The resin materials used in traditional ion exchange resin technology are expensive. The present invention can reduce the separation cost by at least 95%.

[0060] (2) The Sr enrichment method provided by the present invention allows sample preparation to be completed in just two hours. The coprecipitated sample obtained by this method can be directly dissolved in nitric acid and then spotted, eliminating the need for further concentration and evaporation of the Sr sample solution. This significantly reduces sample evaporation time. Compared to the traditional Sr separation process using ion exchange resins, which typically takes 6 to 9 hours, this method improves preparation efficiency by at least three times.

[0061] (3) The Sr enrichment method provided by the present invention can simplify half of the tedious experimental preparation work in traditional ion exchange resin technology (such as cleaning the chromatographic column, cleaning the resin, and multi-step elution with different concentrations of hydrochloric acid or nitric acid), reduce labor consumption, make the operation process simpler, and reduce the rate of human operational errors caused by complex preparation processes.

[0062] (4) The Sr enrichment method provided by the present invention produces almost no excess waste liquid and consumes only a small amount (0.5-1 mL) of hydrofluoric acid and hydrochloric acid, while traditional ion exchange resin technology requires 20-100 mL of hydrochloric acid or nitric acid to complete the preparation. Therefore, the present invention is green and environmentally friendly.

[0063] In summary, the testing method provided by the present invention has high separation efficiency, low testing cost, and is easy to operate. It is suitable for high-precision Sr isotope analysis of wine samples. It is an important innovation in thermal ionization mass spectrometry technology and has broad application prospects in the origin and quality traceability of wine and related foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a schematic flow chart of a method for testing strontium isotopes in wine provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0067] In the following examples, the raw materials used are from:

[0068] MOS-grade hydrofluoric acid (China National Pharmaceutical Group Co., Ltd.); MOS-grade nitric acid (China National Pharmaceutical Group Co., Ltd.); MOS-grade hydrochloric acid (China National Pharmaceutical Group Co., Ltd.); premium-grade phosphoric acid (China National Pharmaceutical Group Co., Ltd.); premium-grade hydrogen peroxide (China National Pharmaceutical Group Co., Ltd.); ultrapure water (Millipore Simplicity ultrapure water system, outlet water conductivity 18.2 MΩ / cm, Millipore Corporation, USA); Sr special-effect resin (Sr Spec, 100-150 μm, Triskem, France).

[0069] The 9 wine samples were randomly purchased in supermarkets, including: W-1 (China, dry red), W-2 (China, dry red), W-3 (China, dry red), W-4 (Spain, dry red), W-5 (Argentina, dry red), W-6 (France, dry red), W-7 (Italy, semi-dry), W-8 (Australia, dry red), and W-9 (Chile, dry red).

[0070] Strontium isotope standard: NBS987, American Standard Material Center; Re filament material: purity 99.98%, H.Cross Company, USA.

[0071] First, the following embodiments of the present invention all use actual wine samples. All wine samples were analyzed for matrix elements and Rb and Sr element concentrations. The matrix elements were measured using a Thermo Fisher IRIS Advantage ICP-OES spectrometer, and Rb and Sr were measured using a Thermo Fisher iCAP Q-ICP quadrupole mass spectrometer. The test results are shown in Table 1.

[0072] Table 1 Element concentration results of each wine sample

[0073]

[0074] In order to evaluate the removal efficiency of matrix elements of actual wine samples by the hydrofluoric acid co-precipitation method, the element concentrations of the supernatant phase after co-precipitation of all wine samples were also tested. The test results are shown in Table 2.

[0075] Table 2 Element concentrations of the coprecipitated supernatant of each wine sample

[0076]

[0077] The matrix element removal rates of different wine samples were calculated from Tables 1 and 2, and the results are shown in Table 3.

[0078] Table 3 Removal efficiency of various elements by co-precipitation of each wine sample

[0079]

[0080] The above elemental analysis data demonstrates that most matrix elements and Rb can be removed in the clear phase. For example, 92.7-99.7% of K, 88.9-97.1% of Na, 83.7-89.7% of B, 80.4-94.3% of Mn, and 93.2-99% of Rb can be removed during the coprecipitation process. During the coprecipitation process, 19.6-39.5% of Sr is lost, resulting in a final Sr recovery of 60.5-80.4% during the coprecipitation process. The average Sr recovery for the nine samples was approximately 67%. The Sr concentration in typical wines ranges from 0.2 to 2 ppm. Considering the most extreme case, even for a sample with a 0.2 ppm concentration, a 3 g sample with a 60% recovery yields approximately 360 ng of Sr. A single TIMS test requires only 3-6 ng of Sr. Therefore, the present invention can meet the sample volume requirements for TIMS testing. Regarding potential Rb interference, the Rb content at the filament surface in different wine samples was less than 2 ng, and it could be quickly burned off during the preheating stage, so it would not interfere with the Sr isotope test.

[0081] To verify the applicability and accuracy of the present invention on actual wine samples, the following specific examples analyzed nine different wine samples for experimental validation. These samples were from seven major wine-exporting countries (France, Australia, Italy, Chile, Argentina, Spain, and China), covering a wide range of Rb-Sr and matrix element concentrations. Sample volumes for each wine sample ranged from 0.5 μL, 1 μL, and 2 μL, corresponding to wine puree weights of 5 mg, 10 mg, and 20 mg, and were analyzed in triplicate. Furthermore, to validate the reliability of the co-precipitation method, the same sample was purified and tested twice using a conventional Sr-specific resin. The analytical results from this conventional technique served as a benchmark to verify the feasibility of the co-precipitation method.

[0082] The Sr special-effect resin separation process provided in an embodiment of the present invention is as follows: a polyethylene micro-exchange column (inner diameter 3 mm) is loaded with 150 μL of Sr special-effect resin (particle size 150 μm), the exchange column is first cleaned with 6 ml of high-purity water and 4.5 ml of 7 mol / L nitric acid, then 0.5 ml of 7 mol / L nitric acid is used to dissolve the sample and load it onto the column, the matrix is ​​cleaned with 3 ml of 7 mol / L nitric acid, and finally the Sr component is eluted with 3 ml of high-purity water, and evaporated to dryness for TIMS testing.

[0083] Example

[0084] like Figure 1 As shown, the embodiment of the present invention provides a method for testing strontium and strontium isotopes in wine. Nine wine samples W-1, W-2, W-3, W-4, W-5, W-6, W-7, W-8, and W-9, each about 3 g (about 3 mL), are taken and tested according to the following method:

[0085] S1. Co-precipitation to obtain Sr sample: Use hydrofluoric acid co-precipitation to capture Sr in wine, and separate and purify to obtain Sr-Ca-Mg fluoride co-precipitation sample; the details are as follows:

[0086] S101. Digestion of wine samples: Place the wine sample in a sample dissolver and place it on a hot plate at 80-90°C to evaporate until it is completely dry; then, add 3mL of 14mol / L concentrated nitric acid and 1mL of 30% hydrogen peroxide, and adjust the hot plate temperature to 80-90°C to nitrate the wine; then, when the sample is evaporated to a black colloidal paste, add 2mL of 14mol / L concentrated nitric acid again and evaporate to dryness at 80-90°C; finally, add 3ml of 14mol / L concentrated nitric acid, keep warm at 150-160°C under sealed conditions for 4-6 hours, open the sample dissolver, unseal it, and evaporate the sample on a hot plate at 150-160°C to remove the organic matter from the wine residue.

[0087] S102. Prepare a strontium sample by co-precipitation separation and purification: Add 0.5 mL of 0.4 mol / L dilute hydrochloric acid to the digested wine residue to dissolve the residue to obtain a residue solution, then add 1 mL of 22 mol / L hydrofluoric acid. Seal the sample dissolver and incubate at 120°C to 130°C for 1.5 to 2 hours to obtain a fluoride co-precipitation sample rich in Sr-Ca-Mg.

[0088] S103. Prepare strontium sample solution: wait until the fluoride co-precipitate cools to room temperature, shake the sample dissolver, transfer the sample suspension to a centrifuge tube, centrifuge for 10 to 15 minutes, then discard the upper clear liquid, add 0.3 mL of 7 mol / L nitric acid to the lower precipitate, shake and dissolve the sample to obtain the strontium sample solution for use.

[0089] Based on the crude Sr ICP-MS concentration, the actual weight of co-precipitated Sr is calculated based on the sample weight and the co-precipitation recovery rate to determine the sample loading amount. Rough Sr elemental measurements are typically performed using an electric-coupled plasma quadrupole mass spectrometer, which typically provides an accuracy of approximately 10% for Sr elemental concentrations. The sample loading amount for the present invention is 1.4 to 35 ng.

[0090] S2. Thermal ionization mass spectrometry for Sr isotope analysis: The sample obtained in step S1 is applied to a high-purity Re filament with a purity higher than 99.8% to perform Sr isotope analysis. The details are as follows:

[0091] S201, take an appropriate amount of 1 μL of 0.2 mol / L dilute phosphoric acid and 1 μL of TaF5 emitter and apply them to the surface of the high-purity Re filament and evaporate them to dryness; then apply 0.5-2 μL of the Sr sample solution prepared in step S1 to the surface of the high-purity Re filament, then increase the current until the filament turns dark red and hold for 4-6 seconds, then return the current to zero;

[0092] S202. Load the loaded filament into the thermal ionization mass spectrometer to obtain the Sr isotope results. The test process is as follows:

[0093] S2021, the thermal ionization mass spectrometer is evacuated to make the ion source vacuum better than 3×10 -7 mabr;

[0094] S2022. Adjust the filament current to 2-2.3 amperes, the heating rate to 500 mA / min, and the corresponding ionization temperature to 1200-1300°C. Preheat at this temperature for 2-3 minutes to eliminate potential Rb interference.

[0095] S2023, open the isolation valve and high voltage, adjust the filament current to 2.62~2.95 amps, the heating rate is 500mA / min, the corresponding ionization temperature is 1450~1520℃, and test the Sr isotope. During the data collection process of the Sr isotope test, 88 The signal intensity of Sr is controlled at 2800~6500mV. 200 sets of data are collected under this signal intensity. 87 Sr / 86 The test accuracy of Sr is better than 0.003% (2RSE). 85 Rb / 86 The Sr ratio is less than 2×10 -5 , indicating that there is no interference from Rb.

[0096] The test results of the methods provided in the embodiments and comparative examples for the nine wine samples W-1, W-2, W-3, W-4, W-5, W-6, W-7, W-8, and W-9 are shown in Tables 4 to 12 below, respectively:

[0097] Table 4 Comparison of the test results of the co-precipitation of wine sample W-1 and the purification with traditional Sr special resin

[0098]

[0099] Note: W-1-0.5, W-1-1, and W-1-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-1-p1 and W-1-p2 are parallel test results after purification with Sr-specific resin.

[0100] Table 5 Comparison of the test results of the co-precipitation of wine sample W-2 and the purification with traditional Sr special resin

[0101]

[0102] Note: W-2-0.5, W-2-1, and W-2-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-2-p1 and W-2-p2 are parallel test results after purification with Sr-specific resin.

[0103] Table 6 Comparison of the test results of the co-precipitation of wine sample W-3 and the purification with traditional Sr special resin

[0104]

[0105] Note: W-3-0.5, W-3-1, and W-3-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-3-p1 and W-3-p2 are parallel test results after purification with Sr-specific resin.

[0106] Table 7 Comparison of the test results of the co-precipitation of wine sample W-4 and the purification with traditional Sr special resin

[0107]

[0108] Note: W-4-0.5, W-4-1, and W-4-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-4-p1 and W-4-p2 are parallel test results after purification with Sr-specific resin.

[0109] Table 8 Comparison of the test results of the co-precipitation of wine sample W-5 and the purification with traditional Sr special resin

[0110]

[0111] Note: W-5-0.5, W-5-1, and W-5-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-5-p1 and W-5-p2 are parallel test results after purification with Sr-specific resin.

[0112] Table 9 Comparison of the test results of the co-precipitation of wine sample W-6 and the purification with traditional Sr special resin

[0113]

[0114] Note: W-6-0.5, W-6-1, and W-6-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-6-p1 and W-6-p2 are parallel test results after purification with Sr-specific resin.

[0115] Table 10 Comparison of the test results of the co-precipitation of wine sample W-7 and the purification with traditional Sr special resin

[0116]

[0117] Note: W-7-0.5, W-7-1, and W-7-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-7-p1 and W-7-p2 are parallel test results after purification with Sr-specific resin.

[0118] Table 11 Comparison of test results of wine sample W-8 co-precipitation and traditional Sr special resin purification

[0119]

[0120] Note: W-8-0.5, W-8-1, and W-8-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-8-p1 and W-8-p2 are parallel test results after purification with Sr-specific resin.

[0121] Table 12 Comparison of test results of wine sample W-9 co-precipitation and traditional Sr special resin purification

[0122]

[0123] Note: W-9-0.5, W-9-1, and W-9-2 represent 0.5 μl, 1 μl, and 2 μl sample loading, respectively. W-9-p1 and W-9-p2 are parallel test results after purification with Sr-specific resin.

[0124] As shown in Tables 4 to 12, for wine samples W-1, W-2, W-3, W-4, W-5, W-6, W-7, W-8, and W-9, the Sr samples obtained by co-precipitation using the present invention and those obtained after purification using traditional ion exchange resins showed consistent results within the analytical error range, demonstrating that the present method is stable and reliable, with extremely high analytical accuracy. The co-precipitation technique proposed in this invention fully meets the requirements for Sr isotope analysis of wine samples. Overall, the internal test accuracy of all samples was better than 0.003% (2RSE), with most samples achieving better than 0.002% (2RSE). All Rb was burned off by filament preheating, and no Rb interference was observed during the testing process.

[0125] The above examples demonstrate that the testing method provided by the present invention can rapidly prepare and perform TIMS testing on Sr isotopes in various common wine samples, and has high testing precision and accuracy. Since traditional ion exchange resin technology is not required, the present invention can reduce preparation costs by at least 95%. Furthermore, the operation is simpler, and the preparation time is shortened by at least 2 times, which can significantly improve preparation efficiency. Furthermore, only 1.5 ml of waste liquid is produced, which is more environmentally friendly and has lower experimental operating costs compared to the traditional Sr special resin purification method, which often produces 30 to 100 mL of highly concentrated waste acid liquid.

[0126] The above descriptions are only some preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for rapidly preparing and testing strontium isotopes in wine, characterized in that: The steps include: S1. Prepare Sr sample by co-precipitation: Use hydrofluoric acid co-precipitation to capture Sr in wine, and separate and purify it to obtain a Sr-Ca-Mg fluoride co-precipitation sample. Based on the crude Sr concentration, the sample weight, and the co-precipitation recovery rate, calculate the actual weight of Sr obtained by co-precipitation to determine the sample spotting amount, which is controlled to be 1.4-35 ng. S2. Thermal ionization mass spectrometry for Sr isotope analysis: The sample obtained in step S1 is placed on a high-purity Re filament to perform Sr isotope analysis. The specific process is as follows: S201, apply an appropriate amount of dilute phosphoric acid and TaF5 emitter to the surface of a high-purity Re filament and evaporate to dryness; then apply an appropriate amount of the prepared Sr sample solution to the surface of the filament and evaporate to dryness, increase the current until the filament turns dark red and hold for 4 to 6 seconds, then return the current to zero; S202. Load the loaded filament into a thermal ionization mass spectrometer to obtain the Sr isotope results. The specific process includes: S2021, evacuation of thermal ionization mass spectrometer; S2022. Adjust the filament current to 2-2.3 amperes, the heating rate to 500 mA / min, and the corresponding ionization temperature to 1200-1300°C. Preheat at this temperature for 2-3 minutes to eliminate potential Rb interference. S2023. Open the isolation valve and high voltage, adjust the filament current to 2.62-2.95 amperes, and the heating rate to 500 mA / min, corresponding to an ionization temperature of 1450-1520°C, and test the Sr isotope.

2. The method for rapid preparation and testing of strontium isotopes in wine according to claim 1, characterized in that: Step S1 is specifically as follows: S101, wine sample digestion: evaporate an appropriate amount of wine sample to dryness, then add preset amounts of concentrated nitric acid and hydrogen peroxide in portions to digest the sample to obtain wine residues free of organic matter; S102. Separate and purify the strontium sample by co-precipitation: dissolve the wine residue with an appropriate amount of dilute hydrochloric acid, add a predetermined amount of hydrofluoric acid, and heat the mixture under closed conditions to obtain a fluoride co-precipitation sample rich in Sr-Ca-Mg; S103. Prepare a strontium sample solution: add a preset amount of nitric acid to dissolve the Sr-Ca-Mg fluoride co-precipitation sample to obtain a strontium sample solution for later use.

3. The method for rapid preparation and testing of strontium isotopes in wine according to claim 1, characterized in that: The amount of Sr sample spotted was 4 to 6 ng.

4. The method for rapid preparation and testing of strontium isotopes in wine according to claim 2, characterized in that: The specific process of wine sample digestion in step S101 is as follows: An appropriate amount of wine sample is weighed and evaporated at 80-90°C until completely dry; then, 14 mol / L concentrated nitric acid and 30% hydrogen peroxide are added in portions to digest the wine sample, the volume ratio of the total volume of the added concentrated nitric acid and hydrogen peroxide to the volume of the wine sample being 3:1, and the amount of hydrogen peroxide used is 1 / 8 of the volume of the concentrated nitric acid used; specifically, all the hydrogen peroxide and an appropriate amount of concentrated nitric acid are first added, and the wine is nitrated at 80-90°C, with the volume ratio of the added concentrated nitric acid to the hydrogen peroxide being 3:1; then, when the wine becomes a black colloidal paste, the remaining concentrated nitric acid is added, and the mixture is kept sealed at 150-160°C for 4-6 hours. After unsealing, the sample is evaporated to dryness at 150-160°C to obtain the digested wine residue.

5. The method for rapid preparation and testing of strontium isotopes in wine according to claim 2, characterized in that: The specific process of steps S102 and S103 is as follows: S102. Add an appropriate amount of dilute hydrochloric acid to the digested wine residue to dissolve it to obtain a residue liquid, then add a preset amount of 22 mol / L hydrofluoric acid, with the volume ratio of hydrofluoric acid to the residue liquid being 2 to 3:1; and keep the mixture at 120° C. to 130° C. under sealed conditions for 1.5 to 2 hours to obtain a fluoride co-precipitation sample rich in Sr-Ca-Mg; S103. Wait until the fluoride co-precipitate cools to room temperature, shake and centrifuge, then discard the supernatant, add a preset amount of nitric acid to the lower precipitate, shake and dissolve the sample to obtain a strontium sample solution for use.

6. The method for rapid preparation and testing of strontium isotopes in wine according to claim 1, characterized in that: During the data collection process of testing Sr isotopes in step S2023, 88 The signal intensity of Sr is controlled between 2800 and 6500 mV.

7. The method for rapid preparation and testing of strontium isotopes in wine according to claim 1, characterized in that: In step S2021, the ion source is vacuumed to a vacuum better than 3×10 -7 mabr.

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