Detection method for determining 26 elements in vegetables and fruits by combining super microwave digestion and ICP-MS (Inductively Coupled Plasma Mass Spectrometry)

Abstract

The invention belongs to the technical field of determination of vegetables and fruits, and discloses a detection method for determining 26 elements in vegetables and fruits by combining super microwave digestion and ICP-MS (Inductively Coupled Plasma Mass Spectrometry). The detection method comprises the following steps: pretreating a vegetable and fruit sample to obtain a sample; the method comprises the following steps: mixing a sample with a nitric acid aqueous solution, and carrying out super microwave digestion to obtain a digestion solution; carrying out constant volume on the digestion solution by adopting ultrapure water to obtain a solution to be detected; and detecting the to-be-detected solution by using an inductively coupled plasma mass spectrometer, determining the ion abundance of the 26 elements in the to-be-detected solution, and calculating the content of the 26 elements in the sample. According to the method, a programmed heating and boosting super microwave digestion method is introduced, so that the problems of long consumed time, insufficient digestion, insufficient uniformity of digestion products, loss of to-be-detected elements and the like in the digestion process are effectively solved, one-time sample preparation and synchronous determination of 26 elements in vegetable and fruit samples are realized, and the method is simple, efficient, safe, reliable and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of vegetable and fruit determination, and in particular to a detection method for determining 26 elements in vegetables and fruits by combining super microwave digestion with ICP-MS. Background Art

[0002] Due to the growing global population, agriculture has experienced rapid growth, inevitably necessitating the use of pesticides and fertilizers to achieve earlier or increased harvests. However, wastewater, waste materials, and domestic sewage generated during agricultural production contain significant amounts of pesticide residues and harmful substances, which can directly or indirectly enter natural water bodies or soil. This has led to increasingly serious contamination of soil-dependent fruit and vegetable crops. When concentrations of these substances exceed safety thresholds, they not only affect the normal growth and development of fruit and vegetable crops but may also induce genetic mutations or even lead to reduced yields and crop failures. More seriously, these harmful substances can gradually accumulate in the human body through the food chain, posing a serious threat to human health. Therefore, elemental testing of fruit and vegetable materials is crucial in the field of food safety. Elemental testing ensures that the nutritional content of fruits and vegetables meets standards while also preventing harmful elements such as heavy metals from harming the human body.

[0003] Currently, the mainstream methods for elemental detection in fruit and vegetable crops include a combination of traditional digestion techniques and spectroscopy / mass spectrometry, rapid detection methods, and new combined technologies. Among these methods, the main technologies used for elemental quantitative analysis are atomic absorption spectrometry (AAS), inductively coupled plasma spectrometry (ICP-AES), X-ray fluorescence spectrometry (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). Among them, inductively coupled plasma mass spectrometry is highly regarded for its excellent performance. It has low detection limits, high sensitivity, and the ability to detect multiple elements simultaneously, making it the most commonly used method. Given that the content of elements such as lead, cadmium, mercury, arsenic, chromium, and cobalt in fruits and vegetables is extremely low, at trace or even trace levels, the application of inductively coupled plasma mass spectrometry is particularly critical. This method only requires one solution to accurately determine more than twenty elements simultaneously, which is extremely advantageous for the detection of low-content elements.

[0004] Although the above quantitative analysis methods have many advantages, to fully exert their efficacy, they need to be配合 with efficient pretreatment techniques. An ideal pretreatment step should ensure that the components to be measured are fully dissolved while avoiding the introduction of impurities. Although there are currently various pretreatment methods, each method has its own limitations. For example, traditional digestion decomposes organic matter by strong acids such as concentrated nitric acid and hydrochloric acid at high temperatures to release the elements to be measured, and combines with spectroscopic techniques for quantitative analysis. However, this method usually requires a digestion time of 4 - 8 hours, with low efficiency; moreover, for high-fiber or high-fat samples, the digestion is incomplete, and carbon residues interfere with the spectral signals. Microwave digestion uses microwave heating to accelerate acidolysis and combines with high-sensitivity mass spectrometry to detect trace elements. However, this method highly depends on the uniformity of the sample, and for tuber or fruit shell samples, fine homogenization is required. Otherwise, local digestion is incomplete, resulting in abnormal recovery rates, and the process of removing acid easily causes the loss of elements to be measured. The dry ashing method removes organic matter by high-temperature ashing and detects after dissolving the ash. However, this method causes partial loss of elements such as arsenic and mercury during ashing above 500°C, and if there are insoluble oxides remaining in the ash, it will increase the complexity of the analysis steps. Summary of the Invention

[0005] The purpose of the present invention is to provide a detection method for determining 26 elements in fruits and vegetables by combining super microwave digestion and ICP-MS, so as to solve the problem that the existing pretreatment methods combined with inductively coupled plasma mass spectrometry cannot accurately detect the element content in fruits and vegetables.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a detection method for determining 26 elements in fruits and vegetables by combining super microwave digestion and ICP-MS, including the following steps:

[0008] (1) Pretreat the fruit and vegetable samples to obtain samples;

[0009] (2) Mix the sample with a nitric acid aqueous solution and perform super microwave digestion to obtain a digestion solution; make up the volume of the digestion solution with ultrapure water to obtain a test solution;

[0010] (3) Detect the test solution with an inductively coupled plasma mass spectrometer, measure the ion abundances of 26 elements in the test solution, and calculate the contents of 26 elements in the sample;

[0011] Among them, in step (2), the temperature-programmed and pressure-boosting conditions of the super microwave digestion are as follows:

[0012] The initial pressure is set to 4 MPa;

[0013] When 0 < T ≤ 10 min, heat up to 140 - 160 °C, and the pressure is set to 10 MPa;

[0014] 10 < T ≤ 20 min, heat up from 140 - 160 °C to 210 - 230 °C, and set the pressure to 12 MPa;

[0015] 20 < T ≤ 40 min, keep the temperature at 210 - 230 °C for heat preservation, and set the pressure to 12 MPa;

[0016] In step (3), the 26 elements include the following element types: lead, cadmium, mercury, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, potassium, sodium, calcium, magnesium, iron, strontium, molybdenum, cobalt, rubidium.

[0017] Preferably, in the detection method, in step (1), the process of the pretreatment includes: sequentially cleaning and crushing the fruit and vegetable samples.

[0018] Preferably, in the detection method, in step (2), the volume ratio of concentrated nitric acid to water in the nitric acid aqueous solution is 1 - 3:1 - 3;

[0019] The mass concentration of concentrated nitric acid in the nitric acid aqueous solution before mixing with water is 60 - 70%.

[0020] Preferably, in the detection method, in step (2), the mass ratio of the sample to the volume of the nitric acid aqueous solution is 0.5 - 1 g:2 - 5 mL.

[0021] Preferably, in the detection method, in step (3), the detection parameters of the inductively coupled plasma mass spectrometer include: the determination mode is the He mode, the helium gas flow rate is 4.5 L / min, the sampling cone is a nickel cone, the sampling depth is 5.0 mm, the radio frequency power is 1500 W, the plasma cooling gas flow rate is 15 L / min, a concentric nebulizer, the nebulizer flow rate is 1.0174 mL / min, the nebulizer chamber temperature is 2 °C, the carrier gas flow rate is 0.8 L / min, the auxiliary gas flow rate is 0.3 L / min, the sample lifting speed is 0.3 r / s, the number of measurement points per peak is 3, and the number of repetitions is 3. [

[0022] Preferably, in the detection method, in step (3), the method for establishing the standard curves of the 26 elements includes the following steps: preparing standard working solutions of the 26 elements with dilute nitric acid; detecting the standard working solutions with an inductively coupled plasma mass spectrometer, and respectively plotting the standard curves of the 26 elements with the concentration of the standard working solutions as the abscissa and the ion abundance as the ordinate. [[ID=二十七]]

[0023] Preferably, in the detection method, the 26 elements are divided into major elements, trace elements and ultra-trace elements;

[0024] The major elements include potassium, sodium, calcium, magnesium, iron;

[0025] The concentration of the standard working solution of the major element is 0-50 μg / mL;

[0026] The trace elements include lead, cadmium, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, strontium, molybdenum, cobalt, and rubidium;

[0027] The concentration of the standard working solution of the trace element is 0 to 0.1 μg / mL;

[0028] The trace elements include mercury;

[0029] The concentration of the standard working solution of the trace element is 0-0.002 μg / mL.

[0030] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention innovatively introduces a super microwave digestion method with programmed temperature and pressure to replace traditional digestion methods. The digestion solution does not need to be acid-driven, effectively overcoming the problems of a long digestion process, insufficient digestion, insufficient uniformity of the digestion product, and loss of the elements to be measured, thereby achieving a one-time sample preparation and simultaneous determination of 26 elements in fruit and vegetable samples. Super microwave digestion can ensure that the fruit and vegetable samples are thoroughly digested, and the resulting solution is clear and transparent with no residue. This not only avoids the problem of difficulty in completely decomposing the sample, but also greatly simplifies the operation process and improves the efficiency and accuracy of the determination. At the same time, this method reduces the amount of reagents used, which is in line with the modern concept of green environmental protection, energy conservation and emission reduction.

[0032] (2) The method for detecting 26 elements in fruits and vegetables described in the present invention is simple, efficient, safe, reliable, and environmentally friendly. During the detection process, non-target impurities in the fruit and vegetable samples do not interfere with the test results, ensuring the accuracy and reliability of the test results. This method has practical application value for improving food safety testing and is of great significance for ensuring food safety. DETAILED DESCRIPTION

[0033] The present invention provides a method for determining 26 elements in fruits and vegetables by combining super microwave digestion with ICP-MS, comprising the following steps:

[0034] (1) Pre-treating the fruit and vegetable samples to obtain samples;

[0035] (2) mixing the sample with a nitric acid aqueous solution and performing super microwave digestion to obtain a digestion solution; and constant-volumeizing the digestion solution with ultrapure water to obtain a test solution;

[0036] (3) Detect the test solution by an inductively coupled plasma mass spectrometer, determine the ion abundances of 26 elements in the test solution, and calculate the contents of the 26 elements in the sample;

[0037] Among them, in step (2), the temperature and pressure programming conditions for the super microwave digestion are as follows:

[0038] The initial pressure is set to 4 MPa;

[0039] When 0 < T ≤ 10 min, heat up to 140 - 160 °C, and the pressure is set to 10 MPa;

[0040] When 10 < T ≤ 20 min, heat up from 140 - 160 °C to 210 - 230 °C, and the pressure is set to 12 MPa;

[0041] When 20 < T ≤ 40 min, keep the temperature at 210 - 230 °C, and the pressure is set to 12 MPa;

[0042] In step (3), the 26 elements include the following element types: lead, cadmium, mercury, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, potassium, sodium, calcium, magnesium, iron, strontium, molybdenum, cobalt, rubidium.

[0043] In the present invention, in step (1), the pretreatment process preferably includes: successively cleaning and crushing the vegetable and fruit samples.

[0044] In the present invention, the cleaning reagent is preferably water; other conditions for cleaning are not limited, and the vegetable and fruit samples can be cleaned thoroughly.

[0045] In the present invention, in step (2), the volume ratio of concentrated nitric acid to water in the nitric acid aqueous solution is preferably 1 - 3:1 - 3, more preferably 1 - 2:1 - 2, and still more preferably 1:1.

[0046] In the present invention, in step (2), the mass concentration of concentrated nitric acid in the nitric acid aqueous solution before mixing with water is preferably 60 - 70%, more preferably 65 - 70%, and still more preferably 70%.

[0047] In the present invention, in step (2), the ratio of the mass of the sample to the volume of the nitric acid aqueous solution is preferably 0.5 - 1 g:2 - 5 mL, more preferably 0.5 - 0.8 g:3 - 4 mL, and still more preferably 0.5 g:3 mL.

[0048] In the present invention, in step (2), the temperature and pressure programming conditions for the super microwave digestion are preferably as follows:

[0049] The initial pressure is set to 4 MPa;

[0050] 0 < T ≤ 10 min, heat up to 140 - 160 °C (further preferably 145 - 155 °C, more preferably 150 °C), and set the pressure to 10 MPa;

[0051] 10 < T ≤ 20 min, heat up from 140 - 160 °C (further preferably 145 - 155 °C, more preferably 150 °C) to 210 - 230 °C (further preferably 215 - 225 °C, more preferably 220 °C), and set the pressure to 12 MPa;

[0052] 20 < T ≤ 40 min, keep the temperature at 210 - 230 °C (further preferably 215 - 225 °C, more preferably 220 °C), and set the pressure to 12 MPa.

[0053] In the present invention, in step (3), the detection parameters of the inductively coupled plasma mass spectrometer preferably include: the determination mode is the He mode, the helium gas flow rate is 4.5 L / min, the sampling cone is a nickel cone, the sampling depth is 5.0 mm, the radio frequency power is 1500 W, the plasma cooling gas flow rate is 15 L / min, a concentric nebulizer, the nebulizer flow rate is 1.0174 mL / min, the nebulizer chamber temperature is 2 °C, the carrier gas flow rate is 0.8 L / min, the auxiliary gas flow rate is 0.3 L / min, the sample lifting speed is 0.3 r / s, the number of measurement points per peak is 3, and the number of repetitions is 3.

[0054] In the present invention, in step (3), the method for establishing the standard curves of the 26 elements preferably includes the following steps: prepare a standard working solution of the 26 elements using dilute nitric acid; detect the standard working solution using an inductively coupled plasma mass spectrometer, and respectively plot the standard curves of the 26 elements with the concentration of the standard working solution as the abscissa and the ion abundance as the ordinate.

[0055] In the method for establishing the standard curves in the present invention, the mass concentration of the dilute nitric acid is preferably 1 - 4%, further preferably 1 - 2%, and more preferably 1.5%.

[0056] In the present invention, the 26 elements are divided into major elements, trace elements and ultra-trace elements.

[0057] In the present invention, the major elements preferably include potassium, sodium, calcium, magnesium, and iron. [[ID=ss]]

[0058] In the present invention, the trace elements preferably include lead, cadmium, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, strontium, molybdenum, cobalt, and rubidium.

[0059] In the present invention, the ultra-trace element preferably includes mercury.

[0060] In the present invention, the concentration of the standard working solution of the major elements is preferably 0-50 μg / mL, specifically preferably 0 μg / mL, 0.5 μg / mL, 1 μg / mL, 5 μg / mL, 10 μg / mL, 30 μg / mL, and 50 μg / mL.

[0061] In the present invention, the concentration of the standard working solution of the trace element is preferably 0-0.1 μg / mL, specifically preferably 0 μg / mL, 0.0005 μg / mL, 0.001 μg / mL, 0.005 μg / mL, 0.01 μg / mL, 0.05 μg / mL, 0.1 μg / mL.

[0062] In the present invention, the concentration of the standard working solution of trace elements is preferably 0-0.002 μg / mL, specifically preferably 0 μg / mL, 0.00001 μg / mL, 0.00005 μg / mL, 0.0001 μg / mL, 0.0005 μg / mL, 0.001 μg / mL, 0.002 μg / mL.

[0063] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0064] In the examples and comparative examples of the present invention, the sample used was GBW10048a (GSB-26a) biological component analysis standard material provided by Wuhan Ruichen Standard Material Technology Co., Ltd. - 20 g of celery, and the pretreatment step was omitted;

[0065] The super microwave digester is Milestone's Ultra Clave super microwave chemistry platform, produced by Milestone in Italy;

[0066] The inductively coupled plasma mass spectrometer (ICP-MS) was an iCAP RQ Ultimate 3000 inductively coupled plasma mass spectrometer (Thermo Fisher Scientific, USA). The following parameters were used: He mode, helium flow rate of 4.5 L / min, nickel sampling cone, sampling depth of 5.0 mm, RF power of 1500 W, plasma cooling gas flow rate of 15 L / min, concentric nebulizer, nebulizer flow rate of 1.0174 mL / min, spray chamber temperature of 2°C, carrier gas flow rate of 0.8 L / min, auxiliary gas flow rate of 0.3 L / min, sample uptake rate of 0.3 r / s, 3 measurement points per peak, and 3 replicates.

[0067] The method for establishing the standard curve of 26 elements includes the following steps:

[0068] (1) The 26 elements are divided into major elements, trace elements and trace elements. The major elements include potassium, sodium, calcium, magnesium and iron. The trace elements include lead, cadmium, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, strontium, molybdenum, cobalt and rubidium. The trace elements include mercury. The standard working solutions of major elements, trace elements and trace elements are prepared by using 1.5wt% dilute nitric acid. The concentrations of the standard working solutions of major elements are 0μg / mL, 0.5μg / mL, 1μg / mL, 5μg / mL, 10μg / mL and 30μg / mL. / mL, 50μg / mL, the concentrations of the standard working solutions of trace elements were 0μg / mL, 0.0005μg / mL, 0.001μg / mL, 0.005μg / mL, 0.01μg / mL, 0.05μg / mL, 0.1μg / mL, and the concentrations of the standard working solutions of trace elements were 0μg / mL, 0.00001μg / mL, 0.00005μg / mL, 0.0001μg / mL, 0.0005μg / mL, 0.001μg / mL, 0.002μg / mL;

[0069] (2) The standard working solution was tested using an inductively coupled plasma mass spectrometer, and standard curves for 26 elements were drawn with the concentration of the standard working solution as the horizontal axis and the ion abundance as the vertical axis;

[0070] The content of the 26 elements in the sample is calculated as follows: the ion abundances of the 26 elements in the test solution are substituted into the standard curve of the 26 elements to obtain the concentrations of the 26 elements in the test solution; then, according to the formula: element content in sample (mg / kg) = element concentration (μg / mL) × fixed volume (mL) ÷ sample mass (g), the content of the 26 elements in the sample is calculated.

[0071] Example 1

[0072] This embodiment provides a method for determining 26 elements in celery by combining super microwave digestion with ICP-MS, comprising the following steps:

[0073] (1) Mix 0.5 g of the celery standard sample with 3 mL of a nitric acid aqueous solution (1.5 mL of 70 wt% concentrated nitric acid: 1.5 mL of ultrapure water), and perform super microwave digestion to obtain a digestion solution. The temperature and pressure programming conditions for super microwave digestion are as follows: The initial pressure is set to 4 MPa; when 0 < T ≤ 10 min, heat up to 150 °C and the pressure is set to 10 MPa; when 10 < T ≤ 20 min, heat up from 150 °C to 220 °C and the pressure is set to 12 MPa; when 20 < T ≤ 40 min, keep it at 220 °C for heat preservation and the pressure is set to 12 MPa; Dilute the digestion solution to 25 mL with ultrapure water to obtain a test solution;

[0074] (2) Detect the test solution using an inductively coupled plasma mass spectrometer, measure the ion abundances of 26 elements in the test solution (including lead, cadmium, mercury, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, potassium, sodium, calcium, magnesium, iron, strontium, molybdenum, cobalt, rubidium), and calculate the contents of 26 elements in the celery standard sample.

[0075] Comparative Example 1

[0076] This comparative example provides a detection method for determining 26 elements in celery by combining thermal digestion and ICP-MS, including the following steps:

[0077] (1) Mix 0.5 g of the celery standard sample with 3 mL of a nitric acid aqueous solution (1.5 mL of 70 wt% concentrated nitric acid: 1.5 mL of ultrapure water), and perform thermal digestion in a graphite digestion instrument to obtain a digestion solution. The temperature rising conditions for thermal digestion are as follows: Heat at 90 °C for 30 min; Gradually heat up to 140 °C and keep it for 4 h; Heat the cooled digestion solution to 150 °C to remove acid until the digestion solution is nearly dry to obtain a digestion product; Dilute the digestion product to 25 mL with ultrapure water and filter (0.45 μm filter membrane) to obtain a test solution; Step (2) is the same as that in Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a detection method for determining 26 elements in celery by combining microwave digestion and ICP-MS, including the following steps:

[0080] (1) 0.5 g of celery standard sample was mixed with 3 mL of nitric acid aqueous solution (1.5 mL of 70 wt% concentrated nitric acid: 1.5 mL of ultrapure water) and subjected to microwave digestion to obtain a digestion solution; the heating conditions for microwave digestion were as follows: microwave power was 1200 W, the temperature was increased from 25° C. to 130° C. in 15 min, and the temperature was kept warm for 30 min; microwave power was 1400 W, the temperature was increased from 130° C. to 180° C. in 15 min, and the temperature was kept warm for 30 min; microwave power was 1500 W, the temperature was increased to 200° C. in 5 min, and the temperature was kept warm for 30 min; the cooled digestion solution was heated to 150° C. to drive out the acid until the digestion solution was almost dry to obtain a digestion product; the digestion product was made up to 25 mL with ultrapure water, and filtered (0.45 μm filter membrane) to obtain a test solution; step (2) was the same as in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a detection method for determining 26 elements in celery by dry ashing digestion combined with ICP-MS, comprising the following steps:

[0083] (1) Place 5 g of celery standard sample in a crucible and heat it to 150°C on a hot plate until the sample is completely carbonized; transfer the carbonized sample to a muffle furnace and gradually increase the temperature to prevent violent combustion: the first stage: maintain at 250°C for 1 hour to allow the organic matter to slowly decompose; the second stage: increase to 500°C and maintain for 6 hours; after the ashing is completed, take out the crucible and cool it to room temperature; use ultrapure water to make the ashing product dilute to 250 mL, and filter (0.45 μm filter membrane) to obtain the test solution; step (2) is the same as in Example 1.

[0084] Comparative Example 4

[0085] This comparative example provides a detection method for determining 26 elements in celery by combining super microwave digestion with ICP-MS. The difference from Example 1 is that the volume of the nitric acid aqueous solution in step (1) is changed to 1 mL (0.5 mL 70 wt% concentrated nitric acid: 0.5 mL ultrapure water), and the other parameter conditions are the same as those in Example 1.

[0086] The element contents in the celery standard sample calculated in Example 1 and Comparative Examples 1 to 4 were compared with the known certified values ​​of the standard sample. The results are shown in Table 1.

[0087] Table 1. Test results of different schemes

[0088]

[0089]

[0090]

[0091] As shown in Table 1, the traditional acid-heat digestion method of Comparative Example 1 requires a long digestion time and low efficiency, and the digestion is incomplete for the high-fiber celery sample, which affects the accuracy of the test. Although the microwave heat digestion of Comparative Example 2 has improved the digestion efficiency compared to Comparative Example 1, the accuracy of the test for high-fiber samples in fruits and vegetables still needs to be improved, and the acid-catching step included can cause the detection results of volatile elements such as arsenic and mercury to be significantly reduced. The dry ashing rule of Comparative Example 3 can obviously cause the detection results of volatile elements such as arsenic and mercury to be abnormal, and the ash filtered out can take away a part of insoluble substances, further reducing the accuracy of the test results. This shows that the closed environment of the super microwave digestion adopted in this application makes it less affected by the outside world, and the error introduced is relatively small. And the test results of Comparative Example 4 are all closer to the identified values ​​than Example 1 on the basis of reducing the amount of nitric acid used, indicating that carrying out super microwave digestion in the nitric acid system of the present invention is more thorough and more accurate, and reducing the amount of nitric acid used can also cause the test results to deviate greatly from the identified values. Therefore, the detection method of the present invention is simple, efficient, safe and reliable, ensuring the accuracy and reliability of the detection results.

[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for determining 26 elements in fruits and vegetables by combining super microwave digestion with ICP-MS, characterized in that: It includes the following steps: (1) Pretreat the fruit and vegetable sample to obtain a sample; (2) Mix the sample with a nitric acid aqueous solution and perform super microwave digestion to obtain a digestion solution; make up the volume of the digestion solution with ultrapure water to obtain a test solution; (3) Detect the test solution with an inductively coupled plasma mass spectrometer, measure the ion abundances of 26 elements in the test solution, and calculate the contents of 26 elements in the sample; Among them, in step (2), the temperature and pressure programming conditions for the super microwave digestion are as follows: The initial pressure is set at 4 MPa; When 0 < T ≤ 10 min, heat up to 140 - 160 °C, and the pressure is set at 10 MPa; When 10 < T ≤ 20 min, heat up from 140 - 160 °C to 210 - 230 °C, and the pressure is set at 12 MPa; When 20 < T ≤ 40 min, keep the temperature at 210 - 230 °C, and the pressure is set at 12 MPa; In step (3), the 26 elements include the following element types: lead, cadmium, mercury, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, potassium, sodium, calcium, magnesium, iron, strontium, molybdenum, cobalt, rubidium.

2. The detection method according to claim 1, wherein In step (1), the process of the pretreatment includes: sequentially cleaning and crushing the fruit and vegetable sample.

3. The detection method according to claim 1, wherein In step (2), the volume ratio of concentrated nitric acid to water in the nitric acid aqueous solution is 1 - 3:1 - 3; The mass concentration of concentrated nitric acid in the nitric acid aqueous solution before mixing with water is 60 - 70%.

4. The detection method according to claim 1 or 3, characterized in that [[ID=[]In step (2), the mass ratio of the sample to the volume of the nitric acid aqueous solution is 0.5 - 1 g:2 - 5 mL.

5. The detection method according to claim 1, wherein In step (3), the detection parameters of the inductively coupled plasma mass spectrometer include: the determination mode is the He mode, the helium gas flow rate is 4.5 L / min, the sampling cone is a nickel cone, the sampling depth is 5.0 mm, the radio frequency power is 1500 W, the plasma cooling gas flow rate is 15 L / min, a concentric nebulizer, the nebulizer flow rate is 1.0174 mL / min, the nebulizer chamber temperature is 2 °C, the carrier gas flow rate is 0.8 L / min, the auxiliary gas flow rate is 0.3 L / min, the sample lifting speed is 0.3 r / s, the number of measurement points per peak is 3, and the number of repetitions is 3.

6. The detection method according to claim 1 or 5, characterized in that In step (3), the method for establishing the standard curves of the 26 elements includes the following steps: prepare standard working solutions of 26 elements with dilute nitric acid; detect the standard working solutions with an inductively coupled plasma mass spectrometer, and respectively plot the standard curves of the 26 elements with the concentration of the standard working solutions as the abscissa and the ion abundances as the ordinate.

7. The detection method according to claim 6, characterized in that The 26 elements are divided into major elements, trace elements and ultra-trace elements; The major elements include potassium, sodium, calcium, magnesium, iron; The concentration of the standard working solution of the major elements is 0 - 50 μg / mL; The trace elements include lead, cadmium, arsenic, chromium, nickel, aluminum, manganese, copper, barium, vanadium, selenium, antimony, tin, lithium, boron, zinc, strontium, molybdenum, cobalt, rubidium; The concentration of the standard working solution of the trace elements is 0 - 0.1 μg / mL; The ultra-trace element includes mercury; The concentration of the standard working solution of the ultra-trace element is 0 - 0.002 μg / mL.

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