Super microwave digestion and conversion rate determination method for organic arsenic in animal and plant sample

Abstract

The invention discloses a super microwave digestion and conversion rate determination method for organic arsenic in animal and plant samples, which comprises the following steps: adding a mixed solution of nitric acid and sulfuric acid into a sample, and performing digestion and cooling by adopting super microwaves to prepare a sample solution; the super microwave digestion conversion rate of the organic arsenic in the animal and plant samples is measured by using inductively coupled plasma mass spectrometry (ICP-MS) and hydride generation-atomic fluorescence spectrometry (HG-AFS). The method has the advantages of simple process, adoption of one-step digestion with super microwaves, no need of repeated acid addition, reduction of energy consumption and cost, short time of super microwave digestion, high conversion rate of super microwave digestion, facilitation of realization of rapid detection, and meeting of requirements of basic food detection.

Description

Technical Field

[0001] The present invention relates to the technical field of pretreatment for arsenic element analysis, and particularly relates to a method for super microwave digestion of organic arsenic in animal and plant samples and determination of its conversion rate. Background Art

[0002] Arsenic exists in various forms in nature, including inorganic arsenic (such as arsenite, arsenate, etc.) and organic arsenic (such as arsenobetaine, arsenocholine, arsenic sugar, etc.). On the one hand, marine products are rich in nutrients and are known as a natural treasure house of trace elements, being natural foods deeply loved by consumers. On the other hand, marine products have the characteristic of enriching arsenic elements in seawater and enter the human body through diet and other channels, distributing throughout the body via the blood, which can cause varying degrees of disorders in histological aspects such as the nervous system, digestive system, respiratory system, and immune system. Therefore, in the food safety detection of marine products, arsenic is a toxic element that has attracted much attention.

[0003] Currently, the methods for determining arsenic content in foods mainly include inductively coupled plasma mass spectrometry (ICP-MS) and hydride generation-atomic fluorescence spectrometry (HG-AFS). ICP-MS can simultaneously determine inorganic arsenic and organic arsenic with high detection accuracy, but the instrument is expensive and the operation cost is high, which is not suitable for popularization in grass-roots laboratories. HG-AFS has low cost and high sensitivity, but is only applicable to the detection of inorganic arsenic and cannot directly detect organic arsenic. Therefore, it is necessary to convert the organic arsenic in the sample into inorganic arsenic through digestion before using HG-AFS to determine the total arsenic content of foods.

[0004] Traditional wet digestion converts organic arsenic into inorganic arsenic through strong oxidizing acids (such as nitric acid, perchloric acid, and sulfuric acid) at high temperatures. This method requires repeated addition of acids, has a long digestion time (several hours), and the conversion of organic arsenic is incomplete. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for super microwave digestion of organic arsenic in animal and plant samples and determination of its conversion rate. Through one-step super microwave digestion, the process is simple and the digestion efficiency is high, which can greatly reduce the detection cost while ensuring the reliability of data.

[0006] The present invention provides a method for super microwave digestion of organic arsenic in animal and plant samples, comprising the following steps: Adding an inorganic mixed acid to the sample, the inorganic mixed acid comprising nitric acid and sulfuric acid with a volume ratio of 2:1, wherein the solid-liquid ratio of the sample to the inorganic mixed acid is 0.05 - 0.1 g / mL; Place the sample added with the inorganic mixed acid in a super microwave digestion instrument for constant-temperature digestion, where the digestion temperature is T °C, 280 < T ≤ 300, and the digestion time is more than 30 min; Cool to obtain a sample solution.

[0007] According to some embodiments of the present invention, the solid-liquid ratio of the inorganic mixed acid is 0.05 g / mL.

[0008] According to some embodiments of the present invention, the specific steps of placing the sample added with the inorganic mixed acid in a super microwave digestion instrument for constant-temperature digestion are as follows: Place the sample added with the inorganic mixed acid in the reaction kettle of the super microwave digestion instrument and seal the reaction kettle; Pre-pressurize with an inert gas in the super microwave digestion instrument; Heat up to T °C and maintain at T °C for constant-temperature digestion for more than 30 min, where 280 < T ≤ 300.

[0009] According to some embodiments of the present invention, the pressure of the pre-pressurization is 3.8 - 4.2 MPa.

[0010] According to some embodiments of the present invention, the sample includes any one of fish, shellfish, crustaceans, and algae.

[0011] According to some embodiments of the present invention, the fish includes salmon or cod; the shellfish includes oyster or scallop; the crustacean includes shrimp; the algae includes laver.

[0012] According to some embodiments of the present invention, the cooling is to cool to below 80 °C.

[0013] The present invention also provides a method for measuring the super microwave digestion conversion rate of organic arsenic in animal and plant samples, including: Measure the total arsenic content A1 of the sample by inductively coupled plasma mass spectrometry (ICP-MS); Digest the sample by the super microwave digestion method of organic arsenic in the above animal and plant samples, and measure the arsenic content A2 of the sample by hydride generation-atomic fluorescence spectrometry (HG-AFS); Calculate the conversion rate, where the conversion rate = (arsenic content A2 measured by HG-AFS / total arsenic content A1 measured by ICP-MS) × 100%.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Simple process: By using an inorganic mixed acid composed of nitric acid and sulfuric acid, the present invention realizes the one-step digestion of organic arsenic in animal and plant samples into inorganic arsenic by means of super microwave, without repeated acid addition, reducing energy consumption and cost. (2) High digestion efficiency: By adjusting the volume ratio of nitric acid and sulfuric acid in the inorganic mixed acid to 2:1, controlling the super microwave digestion temperature at T °C (280 < T ≤ 300), and maintaining it for more than 30 minutes to digest the organic arsenic in animal and plant samples, the shortest digestion time is 30 minutes, which is conducive to the realization of rapid detection and the development of grass-roots laboratory detection.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. Specific embodiments

[0016] In order to make the purpose and technical solutions of the present invention clearer and easier to understand. The following further details the present invention in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] In the description of the present invention, the meaning of several is one or more, the meaning of multiple is more than two, understandings such as greater than, less than, exceeding, etc. do not include the present number, and understandings such as above, below, within, etc. include the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0018] In the following embodiments, raw materials, reagents or devices, if not otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0019] On the one hand, the present invention provides a super microwave digestion method for organic arsenic in animal and plant samples.

[0020] A super microwave digestion method for organic arsenic in animal and plant samples according to an embodiment of the present invention includes the following steps: S21. Add an inorganic mixed acid to the sample. It should be noted that the inorganic mixed acid includes nitric acid and sulfuric acid with a volume ratio of 2:1; the sample includes any one of fish, shellfish, crustaceans or algae; further, the fish includes salmon or cod, the shellfish includes oyster or scallop, the crustacean includes shrimp, and the algae includes laver; wherein, the solid-liquid ratio of the sample to the inorganic mixed acid is 0.05 - 0.1 g / mL. S22. Place the sample added with inorganic mixed acid in a super microwave digestion instrument for constant-temperature digestion, where the digestion temperature is T °C, 280 < T ≤ 300, and the digestion time is more than 30 min; The specific steps include: placing the sample added with inorganic mixed acid in the reaction kettle of the super microwave digestion instrument, sealing the reaction kettle; pre-adding an inert gas in the super microwave digestion instrument for pre-pressurization; heating up to T °C, 280 < T ≤ 300, and maintaining for more than 30 min for constant-temperature digestion; It should be noted that the pre-pressurization pressure is 3.8 - 4.2 MPa; S23. Cool to obtain a sample solution; It should be noted that after the super microwave digestion is completed, cool to below 80 °C to obtain a sample solution; Specifically, weigh 0.3 - 0.5 g (accurate to 0.001 g) of the sample into a clean digestion tank, and then add 5 - 6 mL of inorganic mixed acid; among them, the inorganic mixed acid is composed of nitric acid and sulfuric acid with a volume ratio of 2:1; place the sample added with inorganic mixed acid in the reaction kettle of the super microwave digestion instrument, seal the reaction kettle; pre- add an inert gas in the super microwave digestion instrument for pre-pressurization, and the pre-pressurization pressure is 3.8 - 4.2 MPa; heat up to T °C, maintain at T °C for constant-temperature digestion for more than 30 min, 280 < T ≤ 300; cool to below 80 °C to obtain a sample solution; transfer the sample solution to a 25 mL volumetric flask or colorimetric tube, wash the digestion tank 3 times with a small amount of sulfuric acid solution, combine the washing solutions in the volumetric flask or colorimetric tube and add 2 mL of a mixed solution of thiourea and ascorbic acid, make up the volume to the scale with sulfuric acid solution, mix well, and let stand for 30 min to prepare a sample solution to be measured.

[0021] On the other hand, the present invention provides a method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples.

[0022] A method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples according to an embodiment of the present invention includes the following steps: S1. Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the total arsenic content A1 of the animal and plant sample; It should be noted that in some embodiments, the test parameters of inductively coupled plasma mass spectrometry are as follows: RF power: 1500 W, plasma gas flow rate: 15 L / min, carrier gas flow rate: 0.80 L / min, auxiliary gas flow rate: 0.4 L / min, helium gas flow rate: 4 - 5 mL / min, nebulizer chamber temperature: 2 °C, sample lifting rate: 0.3 r / s, nebulizer: high salt / concentric nebulizer, sampling cone / interception cone: nickel / platinum cone; sampling depth: 8 - 10 mm, acquisition mode: peak jumping, detection method: automatic, number of measurement points per peak: 1 - 3, number of repetitions: 2 - 3; Specifically, prepare the standard solution and the sample to be tested solution B1 according to the first method of GB5009.268 - 2016; inject the standard solution into the inductively coupled plasma mass spectrometer, measure the signal response values of arsenic element and internal standard element, take the arsenic content as the abscissa, and the ratio of the response signal value of arsenic element to the selected internal standard element as the ordinate to draw the standard curve; inject the blank solution and the sample to be tested solution B1 into the inductively coupled plasma mass spectrometer respectively, measure the signal response values of arsenic element and internal standard element, and obtain the total arsenic content A1 of the animal and plant samples according to the standard curve.

[0023] S2. Digest the organic arsenic in the animal and plant samples by using the above - mentioned super - microwave digestion method for organic arsenic in animal and plant samples; It should be noted that the sample to be tested solution B2 is obtained by digesting the organic arsenic in the animal and plant samples by using the above - mentioned super - microwave digestion method for organic arsenic in animal and plant samples.

[0024] S3. Determine the arsenic content A2 of the animal and plant sample solution by using hydride generation - atomic fluorescence spectrometry (HG - AFS); It should be noted that in some embodiments, the test parameters of hydride generation - atomic fluorescence spectrometry are as follows: element lamp: arsenic, atomizer temperature: 200 °C, atomizer height: 6 - 8 mm, photomultiplier negative high voltage: 240 - 280 V, total current of arsenic hollow cathode lamp: 50 - 80 mA, carrier gas flow rate: 400 - 600 mL / min, shielding gas flow rate: 700 - 900 mL / min; preferably, the test parameters of hydride generation - atomic fluorescence spectrometry are: element lamp: arsenic, atomizer temperature: 200 °C, atomizer height: 8 mm, photomultiplier negative high voltage: 260 V, total current of arsenic hollow cathode lamp: 50 - 80 mA, carrier gas flow rate: 500 mL / min, shielding gas flow rate: 800 mL / min; Specifically, prepare the standard solution according to the first method of GB5009.11-2024. Introduce the standard solution and the blank solution into the instrument in sequence for the determination of atomic fluorescence intensity. Use the atomic fluorescence intensity as the ordinate and the arsenic content as the abscissa to make a standard curve and obtain the regression equation. Introduce the sample solution to be measured B2 into the instrument for the determination of atomic fluorescence intensity, and calculate the arsenic content A2 of the animal and plant sample solution according to the regression equation.

[0025] S4. Calculate the conversion rate, where the conversion rate = (arsenic content A2 measured by HG-AFS / total arsenic content A1 measured by ICP-MS) x 100%.

[0026] For easier understanding and implementation of the present invention, the following provides more easily implemented and more specific and detailed embodiments for reference. Through the description and performance results of the following specific embodiments, the embodiments of the present invention and their advantages will also be obvious. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, giving detailed implementation methods and specific operation processes, only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention, and the protection scope of the present invention is not limited to the following embodiments.

[0027] The instruments selected for each embodiment and comparative example of the present invention are described as follows: The model of the super microwave digestion instrument is: SUPERMATE 7X type super microwave digestion / extraction instrument.

[0028] The test parameters of inductively coupled plasma mass spectrometry are: RF power: 1500 W, plasma gas flow rate 15 L / min, carrier gas flow rate: 0.80 L / min, auxiliary gas flow rate: 0.4 L / min, helium gas flow rate: 4 - 5 mL / min, nebulizer chamber temperature: 2 °C, sample uptake rate: 0.3 r / s, nebulizer: high salt / concentric nebulizer, sampling cone / interception cone: nickel / platinum cone; sampling depth: 8 - 10 mm, acquisition mode: peak jumping, detection method: automatic, number of measurement points per peak: 1 - 3, number of repetitions: 2 - 3.

[0029] The test parameters of hydride generation-atomic fluorescence spectrometry are: element lamp: arsenic, atomizer temperature 200 °C, atomizer height: 8 mm, photomultiplier negative high voltage: 260 V, total current of arsenic hollow cathode lamp: 50 - 80 mA, carrier gas flow rate: 500 mL / min, shielding gas flow rate: 800 mL / min.

[0030] Some of the reagents selected for each embodiment and comparative example of the present invention are described as follows: Nitric acid: mass fraction 65 - 68%, guaranteed reagent G.R., Guangzhou Chemical Reagent Factory.

[0031] Sulfuric acid: mass fraction 95 - 98%, analytical reagent grade A.R., Guangzhou Chemical Reagent Factory.

[0032] Example 1 In this example, the plant and animal sample used is 0.3 g of the organic arsenic component analysis reference material laver powder GBW10023.

[0033] This example provides a method for determining the conversion rate of super microwave digestion of organic arsenic in plant and animal samples (the process includes the super microwave digestion method of organic arsenic in plant and animal samples), which includes the following steps: S1. Use inductively coupled plasma mass spectrometry (ICP - MS) to determine the total arsenic content A1 of the plant and animal sample; According to the first method of GB5009.268 - 2016, prepare the standard solution and the sample to be measured solution B1 of the organic arsenic component analysis reference material laver powder GBW10023; inject the standard solution into the inductively coupled plasma mass spectrometer, measure the signal response values of arsenic element and internal standard element, take the arsenic content as the abscissa, and the ratio of the response signal value of arsenic element to the selected internal standard element as the ordinate to draw the standard curve; inject the blank solution and the sample to be measured solution B1 of the organic arsenic component analysis reference material laver powder GBW10023 into the inductively coupled plasma mass spectrometer respectively, measure the signal response values of arsenic element and internal standard element, and obtain the total arsenic content A1 of the organic arsenic component analysis reference material laver powder GBW10023 according to the standard curve.

[0034] S2. Use the above - mentioned super microwave digestion method of organic arsenic in plant and animal samples to digest the plant and animal samples; S21. Add inorganic mixed acid to the sample; Specifically, accurately weigh 0.3 g of the organic arsenic component analysis reference material laver powder GBW10023 and place it in a clean digestion tank, then add 6 mL of inorganic mixed acid; among them, the inorganic mixed acid is composed of nitric acid and sulfuric acid with a volume ratio of 2:1. S22. Place the sample added with inorganic mixed acid in a super microwave digester for constant - temperature digestion, where the digestion temperature is 300 °C and the digestion time is more than 30 min; Specifically, place the sample added with inorganic mixed acid in the reaction kettle of the super microwave digester, seal the reaction kettle; pre - charge inert gas in the super microwave digester for pre - pressurization, and the pre - pressurization pressure is 4.0 MPa; heat up to 300 °C and keep at 300 °C for constant - temperature digestion for 30 min; S23. Cool to obtain the sample solution; Specifically, cool it to below 80 °C to obtain a sample solution; transfer the sample solution to a 25 mL volumetric flask or colorimetric tube, wash the digestion tank 3 times with a small amount of sulfuric acid solution, combine the washing solutions in the volumetric flask or colorimetric tube, add 2 mL of a mixed solution of thiourea and ascorbic acid, make up the volume to the mark with sulfuric acid solution, mix well, and let it stand for 30 min to prepare the sample test solution B2. S3. Determine the arsenic content A2 of the animal and plant sample solution by hydride generation-atomic fluorescence spectrometry (HG-AFS). Specifically, prepare a standard solution according to the first method of GB5009.11-2024. Introduce the standard solution and blank solution into the instrument in turn for the determination of atomic fluorescence intensity. Take the atomic fluorescence intensity as the ordinate and the arsenic content as the abscissa to make a standard curve and obtain a regression equation; introduce the sample test solution B2 into the instrument for the determination of atomic fluorescence intensity, and calculate the arsenic content A2 of the organic arsenic component analysis reference material laver powder GBW10023 according to the regression equation.

[0035] S4. Calculate the conversion rate, where the conversion rate = (arsenic content A2 determined by HG-AFS / total arsenic content A1 determined by ICP-MS) × 100%.

[0036] Example 2 This example provides a method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 1 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0037] Example 3 This example provides a method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 1 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0038] Example 4 This example provides a method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 1 is that the constant temperature digestion time is 60 min.

[0039] Example 5 This example provides a method for determining the super microwave digestion conversion rate of organic arsenic in animal and plant samples (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0040] Example 6 This example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0041] Comparative Example 1 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 1 is that the constant temperature digestion time is 15 min.

[0042] Comparative Example 2 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 1 is that 0.3 g of cod fish meal ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0043] Comparative Example 3 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 1 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0044] Comparative Example 4 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that the constant temperature digestion is carried out at 280 °C.

[0045] Comparative Example 5 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that the constant temperature digestion is carried out at 260 °C.

[0046] Comparative Example 6 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 4 is that 0.3 g of cod fish meal ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0047] Comparative Example 7 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 5 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0048] Comparative Example 8 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 4 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0049] Comparative Example 9 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 5 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0050] Comparative Example 10 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that 6 mL of inorganic mixed acid composed of nitric acid and sulfuric acid with a volume ratio of 1:2 is added.

[0051] Comparative Example 11 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that 6 mL of inorganic mixed acid composed of nitric acid and sulfuric acid with a volume ratio of 1:1 is added.

[0052] Comparative Example 12 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Example 4 is that 6 mL of inorganic mixed acid composed of 100% nitric acid is added.

[0053] Comparative Example 13 This comparative example provides a method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organic arsenic in animal and plant samples). The difference from Comparative Example 10 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0054] Comparative Example 14 This comparative example provides a method for determining the conversion rate of organoarsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organoarsenic in animal and plant samples). The difference from Comparative Example 11 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0055] Comparative Example 15 This comparative example provides a method for determining the conversion rate of organoarsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organoarsenic in animal and plant samples). The difference from Comparative Example 12 is that 0.3 g of cod meat powder ERM-BB422 is used instead of 0.3 g of laver powder GBW10023.

[0056] Comparative Example 16 This comparative example provides a method for determining the conversion rate of organoarsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organoarsenic in animal and plant samples). The difference from Comparative Example 10 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0057] Comparative Example 17 This comparative example provides a method for determining the conversion rate of organoarsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organoarsenic in animal and plant samples). The difference from Comparative Example 11 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0058] Comparative Example 18 This comparative example provides a method for determining the conversion rate of organoarsenic in animal and plant samples by super microwave digestion (the process includes the super microwave digestion method of organoarsenic in animal and plant samples). The difference from Comparative Example 12 is that 0.3 g of oyster powder 1566B is used instead of 0.3 g of laver powder GBW10023.

[0059] Analysis of experimental results of examples and comparative examples 1. Conduct digestion experiments on organoarsenic in different animal and plant samples by super microwave isothermal digestion under different time conditions To study the influence of different isothermal digestion times maintained by super microwave on the digestion degree of organoarsenic in different animal and plant samples, Examples 1-6 and Comparative Examples 1-3 used laver powder GBW10023, cod meat powder ERM-BB422, and oyster powder 1566B as samples, and an inorganic mixed acid of 4 ml of nitric acid + 2 ml of sulfuric acid (nitric acid: sulfuric acid (v / v) = 2:1) as the acid system. Using a super microwave digester to maintain an isothermal digestion at 300 °C for different times, the experimental results of Examples 1-6 and Comparative Examples 1-3 were calculated and analyzed, as shown in Table 1 specifically: Table 1 As can be seen from Table 1, after 30 minutes of super microwave digestion of organic arsenic in animal and plant samples, the conversion rate of organic arsenic can reach over 90%, and after 60 minutes of digestion, complete conversion of organic arsenic can be achieved; it shows that the super microwave digestion method of organic arsenic in animal and plant samples of the present invention and the method for measuring its conversion rate (in a mixed inorganic acid system where the volume ratio of nitric acid to sulfuric acid is 2:1, controlling the super microwave digestion temperature at 300 °C and maintaining for more than 30 minutes) can basically digest the organic arsenic in animal and plant samples under the conditions of only one super microwave digestion and a short digestion time, improve the accuracy of detecting arsenic content in animal and plant samples by HG-AFS, and is conducive to the realization of rapid detection and meeting the needs of grass-roots food detection.

[0060] 2. Super microwave constant temperature digestion experiment of organic arsenic in different animal and plant samples under different temperature conditions In order to study the influence of super microwave constant temperature digestion at different temperatures on the digestion degree of organic arsenic in different animal and plant samples, Examples 4 - 6 and Comparative Examples 4 - 9 used laver powder GBW10023, cod meat powder ERM-BB422, and oyster powder 1566B as samples, and an inorganic mixed acid of 4 ml nitric acid + 2 ml sulfuric acid (nitric acid: sulfuric acid (v / v) = 2:1) as the acid system. The super microwave digester was used to maintain different temperatures for constant temperature digestion for 60 minutes. The experimental results of Examples 4 - 6 and Comparative Examples 4 - 9 were calculated and analyzed, as shown in Table 2 specifically: Table 2 As can be seen from Table 2, the super microwave digestion of organic arsenic in animal and plant samples at 300 °C can achieve complete conversion of organic arsenic; although for the animal and plant samples of laver powder GBW10023 and oyster powder 1566B, under the conditions of a digestion temperature of 280 °C, a volume ratio of nitric acid to sulfuric acid of 2:1 in the mixed inorganic acid, and a constant temperature digestion time of 60 minutes for super microwave digestion, the conversion rate of organic arsenic reaches over 90%, but for another animal sample, cod meat powder ERM-BB422, the conversion rate of organic arsenic is only 67%; it shows that the super microwave digestion method of organic arsenic in animal and plant samples of the present invention and the method for measuring its conversion rate (in a mixed inorganic acid system where the volume ratio of nitric acid to sulfuric acid is 2:1, controlling the super microwave digestion temperature at 300 °C and maintaining for 60 minutes) can completely digest the organic arsenic in animal and plant samples under the conditions of only one super microwave digestion and a short digestion time, improve the accuracy of detecting arsenic content in animal and plant samples by HG-AFS, and is conducive to the realization of rapid detection and meeting the needs of grass-roots food detection.

[0061] 3. Carry out digestion experiments on organic arsenic in different animal and plant samples by super microwave constant temperature digestion under different volume ratios of nitric acid and sulfuric acid To study the influence of different volume ratios of nitric acid and sulfuric acid in inorganic mixed acids on the digestion degree of organic arsenic in different animal and plant samples, Examples 4-6 and Comparative Examples 10-18 used laver powder GBW10023, cod fish powder ERM-BB422, and oyster powder 1566B as samples, with different acid systems, and used a super microwave digester to maintain a constant temperature of 300 °C for 60 min. Calculate and analyze the experimental results of Examples 4-6 and Comparative Examples 10-18, as shown in Table 3 specifically: Table 3 As can be seen from Table 3, the super microwave digestion conversion rate of organic arsenic in animal and plant samples is the highest under the ratio system of nitric acid: sulfuric acid = 2:1; under the condition that the total amount of inorganic acid used remains unchanged, too large or too small volume ratio of sulfuric acid in the inorganic mixed acid will affect the digestion efficiency of organic arsenic in animal and plant samples by super microwave digestion; it shows that the super microwave digestion method and its conversion rate determination method for organic arsenic in animal and plant samples of the present invention (in the mixed inorganic acid system, the volume ratio of nitric acid and sulfuric acid is 2:1, controlling the super microwave digestion temperature at 300 °C and maintaining for 60 min) can completely digest organic arsenic in animal and plant samples under the condition of only one super microwave digestion and a short digestion time, improve the accuracy of detecting arsenic content in animal and plant samples by HG-AFS, and is conducive to the realization of rapid detection and meeting the needs of grass-roots food detection.

[0062] In summary, the present invention provides a method for super microwave digestion and its conversion rate determination of organic arsenic in animal and plant samples, which can convert organic arsenic in the samples into inorganic arsenic in one step by super microwave in a short time, facilitating subsequent accurate measurement of the arsenic content in animal and plant samples by hydride generation-atomic fluorescence spectrometry. This method uses an optimized mixed inorganic acid ratio (the volume ratio of nitric acid and sulfuric acid is 2:1) combined with super microwave at T °C (280 < T ≤ 300), and the constant temperature digestion can completely convert the organic arsenic in the samples into inorganic arsenic in only 30 min at the shortest digestion time, which is conducive to subsequent selection of the more inexpensive hydride generation-atomic fluorescence spectrometry to accurately measure the arsenic content of the samples. At the same time, its process is simple, without repeated addition of acid, reducing energy consumption and cost, and the digestion time is short, which is conducive to the realization of rapid detection and meeting the needs of grass-roots food detection.

[0063] The above embodiments only illustrate several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A method for super microwave digestion of organic arsenic in animal and plant samples, characterized in that, Comprising the following steps: Adding an inorganic mixed acid to the sample, the inorganic mixed acid comprising nitric acid and sulfuric acid in a volume ratio of 2:1, wherein the solid-liquid ratio of the sample to the inorganic mixed acid is 0.05 - 0.1 g / mL; Placing the sample added with the inorganic mixed acid in a super microwave digestion instrument for constant-temperature digestion, wherein the digestion temperature is T °C, 280 < T ≤ 300, and the digestion time is more than 30 min; Cooling to obtain a sample solution.

2. The super microwave digestion method for organic arsenic in animal and plant samples according to claim 1, characterized in that, The solid-liquid ratio of the inorganic mixed acid is 0.05 g / mL.

3. A method for super microwave digestion of organic arsenic in animal and plant samples according to claim 1, characterized in that, The specific steps of placing the sample added with the inorganic mixed acid in a super microwave digestion instrument for constant-temperature digestion are: Placing the sample added with the inorganic mixed acid in the reaction kettle of the super microwave digestion instrument and sealing the reaction kettle; Pre-pressurizing with an inert gas in the super microwave digestion instrument; Heating to T °C and maintaining at T °C for constant-temperature digestion for more than 30 min, wherein 280 < T ≤ 300.

4. A super microwave digestion method for organic arsenic in animal and plant samples according to claim 3, characterized in that, The pressure of the pre-pressurization is 3.8 - 4.2 MPa.

5. A method for super microwave digestion of organic arsenic in animal and plant samples according to claim 1, characterized in that, The sample includes any one of fish, shellfish, crustaceans, and algae.

6. The super microwave digestion method for organic arsenic in animal and plant samples according to claim 5, characterized in that, The fish includes salmon or cod; the shellfish includes oyster or scallop; the crustaceans include shrimp; the algae includes laver.

7. A method for super microwave digestion of organic arsenic in animal and plant samples according to claim 1, characterized in that, The cooling is to cool to below 80 °C.

8. A method for determining the conversion rate of organic arsenic in animal and plant samples by super microwave digestion, characterized in that, Including: Determining the total arsenic content A1 of the sample by inductively coupled plasma mass spectrometry (ICP-MS); Digesting the sample by the super microwave digestion method for organic arsenic in animal and plant samples according to any one of claims 1 - 7; Determining the arsenic content A2 of the sample by hydride generation-atomic fluorescence spectrometry (HG-AFS); Calculating the conversion rate, wherein the conversion rate = (arsenic content A2 determined by HG-AFS / total arsenic content A1 determined by ICP-MS) × 100%.

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