A leaching agent for leaching soil available elements, and a leaching detection method and application thereof

Abstract

This invention discloses an extractant for extracting available elements from soil, its extraction detection method, and its application. The extractant is composed of acetic acid, ammonium nitrate, ammonium fluoride, amino acid ionic liquid, citric acid, biosurfactant, and deionized water. Through the synergistic effect of multiple components, it achieves efficient and selective extraction of strontium, calcium, magnesium, and potassium. The extract is analyzed simultaneously using inductively coupled plasma atomic emission spectrometry (ICP-AES), featuring simple operation, good reproducibility, and high precision. Verification using multiple soil samples showed a significant positive correlation between the extracted strontium content and the strontium content in maize kernels (R=0.928, R0.928). 2 =0.861, P<0.01), which can truly reflect the soil's ability to supply nutrients to crops and is suitable for strontium-enriched functional agriculture, soil fertility assessment and precision fertilization guidance.

Description

Technical Field

[0001] This invention relates to the field of soil chemical analysis technology, specifically to an extractant for the simultaneous extraction of available strontium, calcium, magnesium, and potassium from soil, as well as a rapid and accurate detection method and application. Background Technology

[0002] Soil-extractable elements refer to the forms of elements in the soil that can be absorbed and utilized by plant roots, including water-soluble, exchangeable, and some bound forms that are easily absorbed by plants. Accurate determination of soil-extractable element content is crucial for assessing soil fertility, guiding precision fertilization, and conducting environmental risk assessments. Traditional soil-available element detection techniques mainly focus on macroelements such as nitrogen, phosphorus, and potassium, while less attention is paid to strontium. Existing research indicates that strontium, as one of the essential microelements in living organisms, plays an important biological role in the human body. Currently, the development and utilization of strontium both domestically and internationally is mainly limited to industry and mining, with very little research on its application in ecological agriculture. Studies on the migration and enrichment characteristics of strontium in soil crops are scarce, and standards for strontium-enriched agricultural products have not been established. These factors severely restrict the development of strontium-enriched ecological agriculture.

[0003] The methods for determining extractable elements in soil mainly include the following: (1) Diethylenetriaminepentaacetic acid (DTPA) extraction method: This is a commonly used method for determining extractable trace elements in soil, such as copper, iron, manganese, and zinc. Its principle is to use the chelating ability of DTPA to extract exchangeable and some bound elements that are easily absorbed by plants in the soil. However, the DTPA extraction method is mainly suitable for trace elements in acidic, neutral, and calcareous soils, and its extraction effect on alkaline earth metal elements such as strontium, calcium, and magnesium is limited. (2) Acetic acid-ammonium acetate buffer solution extraction method: This method is mainly used to determine available phosphorus, potassium, calcium, magnesium, and other elements in soil. This method extracts exchangeable cations in soil through the ion exchange of acetic acid-ammonium acetate buffer solution. However, the pH value of acetic acid-ammonium acetate buffer solution is usually neutral or weakly acidic, and the extraction effect on extractable strontium is not ideal. (3) Hydrochloric acid extraction method: This method is mainly used for the extraction of extractable metal elements in acidic soils. Hydrochloric acid's strong acidity can dissolve some insoluble compounds, but it may damage the original structure of the soil and may interfere with the determination of elements such as calcium and magnesium. (4) Sodium bicarbonate extraction method: mainly used to determine the content of available phosphorus in soil. Its principle is to use bicarbonate ions to form complexes with metal ions such as iron and aluminum, thereby releasing phosphorus bound to these metals. This method has limited extraction effect on elements such as strontium, calcium, and magnesium.

[0004] The main problems with the above-mentioned methods for determining extractable elements are: (1) Incomplete element coverage: Current standard methods (such as HJ 804-2016) are only applicable to the determination of eight extractable elements, including copper, iron, manganese, zinc, cadmium, cobalt, nickel, and lead. There is a lack of extractable extraction and determination methods for strontium. (2) Insufficient simultaneous detection of multiple elements: Traditional methods usually require the use of different extractants to extract different elements and then to determine them using different detection methods, resulting in a complex, time-consuming, and costly detection process. (3) Limitations of detection methods: Although atomic absorption spectrometry (AAS) has high detection accuracy, it can only determine single elements. Furthermore, the detection of high-content elements requires sample dilution, which increases the workload of pretreatment. (4) Lack of standards: There are currently no national or industry standards for extractable strontium in soil, resulting in a lack of unified technical specifications for related research and applications.

[0005] Currently, domestic research on strontium determination mainly focuses on industrial, ores, and radioactive Sr-89 and Sr-90. There are no reports on the extraction and determination of available strontium in soil. In addition, for many years, scholars at home and abroad have been committed to the research of universal extraction agents, achieving the simultaneous extraction of multiple elements through the combination of different chemical substances. However, no special extraction agent or detection method has yet been found for the simultaneous extraction of available strontium, available calcium, available magnesium, and available potassium in soil.

[0006] Existing research reports have not clearly established the correlation between extractable elements obtained from extractants and the soil's ability to supply nutrients to crops. Therefore, developing an extractant and corresponding detection method that can rapidly, accurately, and efficiently determine the content of available strontium, available calcium, available magnesium, and available potassium in soil samples, and establishing a quantitative relationship between the extractable elements obtained from this extractant and the soil's ability to supply nutrients to crops, has significant practical application value for scientifically assessing soil fertility and guiding the safe cultivation of strontium-rich agricultural products. Summary of the Invention

[0007] The main objective of this invention is to provide an extractant and its detection method that can simultaneously extract and rapidly and accurately detect available strontium, calcium, magnesium, and potassium in soil. This method can efficiently and selectively extract available strontium from soil, while simultaneously extracting it along with calcium, magnesium, and potassium. Furthermore, it establishes a quantitative relationship between the extracted strontium and the soil's ability to supply nutrients to crops, providing important guidance for soil fertility assessment and the safe cultivation of strontium-rich agricultural products.

[0008] This invention provides an extractant for extracting effective elements from soil, comprising the following components: 0.1-0.3 mol / L acetic acid, 0.1-0.4 mol / L ammonium nitrate, 0.01-0.03 mol / L ammonium fluoride, 0.01-0.02 mol / L amino acid ionic liquid, 0.03-0.12 mol / L citric acid, 0.005-0.02 mol / L biosurfactant, and the remainder being deionized water.

[0009] Preferably, the biosurfactant is at least one of cocamidopropyl betaine, dodecyl dimethyl betaine, and dodecyl hydroxypropyl sulfobetaine.

[0010] Preferably, the amino acid ionic liquid is at least one of aspartic acid hydrochloride, glycine hydrochloride, and alanine nitrate.

[0011] Preferably, the extractant for extracting effective elements from the soil consists of 0.2 mol / L acetic acid, 0.25 mol / L ammonium nitrate, 0.015 mol / L ammonium fluoride, 0.015 mol / L aspartic acid hydrochloride, 0.1 mol / L citric acid, 0.01 mol / L cocamidopropyl betaine, and the remainder being deionized water.

[0012] This invention provides a method for preparing an extractant for extracting effective elements from soil, comprising the following steps:

[0013] Dissolve acetic acid, ammonium nitrate, and ammonium fluoride in water, add amino acid ionic liquid, citric acid, and biosurfactant, stir until completely dissolved, and then bring the volume to the required level with deionized water.

[0014] Preferably, the stirring process is carried out at a speed of 300-500 r / min, a temperature of 20-40℃, and a stirring time of 30-120 min.

[0015] This invention also provides an application of an extractant in soil testing, used for the simultaneous extraction of available strontium, calcium, magnesium, and potassium from soil.

[0016] This invention also provides a method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using an extraction agent, comprising the following steps:

[0017] Weigh out the air-dried soil sample that has passed through a 0.2 mm sieve, add the extractant at a solid-liquid ratio of 1:10-15, and extract by shaking at 150-300 times / minute for 10-60 minutes. Separate the solid and liquid, collect the filtrate, and determine the contents of strontium, calcium, magnesium, and potassium in the filtrate.

[0018] Preferably, the temperature for the oscillation extraction is 20-40 degrees Celsius.

[0019] Preferably, the filtrate is tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0020] Preferably, the operating parameters of the inductively coupled plasma atomic emission spectrometer are as follows: emission power 1150W, cooling gas flow rate 13.5L / min, auxiliary gas flow rate 1.0L / min, nebulizing gas flow rate 1.0L / min, sample rinsing time 15s, analysis pump speed 50rpm, rinsing pump speed 50rpm, optical chamber temperature 38℃, detector cooling temperature -40℃, and carrier gas argon.

[0021] Preferably, the analytical spectral wavelengths for the tested strontium, calcium, magnesium, and potassium elements are 407.7 nm for strontium, 317.9 nm for calcium, 285.2 nm for magnesium, and 766.4 nm for potassium.

[0022] The extraction agent used in this application exhibits unique advantages in extraction efficiency and selectivity through the combination of biosurfactants, amino acid ionic liquids, and citric acid. Through the synergistic effect of multiple components, highly efficient simultaneous extraction of strontium, calcium, magnesium, and potassium from soil is achieved. Its core working principle can be summarized as follows:

[0023] 1. Acetic acid provides and maintains a weakly acidic environment, pH 3.5–4.5, which promotes the protonation of soil colloid surfaces, thereby significantly enhancing the exchange efficiency of ammonium ions in ammonium nitrate with strontium, calcium, magnesium, potassium and other cations adsorbed in the soil. At the same time, its buffering capacity ensures the stability of the reaction system.

[0024] 2. Ammonium fluoride can form stable complexes with competing metals such as aluminum and iron, reducing the adsorption of strontium by these elements and significantly improving the extraction efficiency of strontium; ammonium nitrate releases exchangeable cations through ion exchange; together, they create a suitable high ionic strength extraction environment.

[0025] Amino acid ionic liquids and citric acid act as dual chelating agents, selectively capturing desorbed metal ions such as strontium, calcium, and magnesium through carboxyl and amino coordination and organic acid complexation capabilities, respectively, forming water-soluble complexes. This continuously drives the extraction equilibrium toward the positive reaction direction and prevents the reprecipitation of strontium, calcium, and magnesium.

[0026] 3. When the concentration of biosurfactants exceeds the critical micelle concentration, they can reduce the surface tension of the extract, enhance its wetting and dispersion of soil particles, and promote the migration of metal chelates from soil micropores into the solution through the micelle structure, effectively inhibiting the re-adsorption of extracted ions.

[0027] This extraction agent not only achieves efficient, stable, and simultaneous extraction of target elements, but also shows a highly significant positive correlation between the extracted available strontium content and plant uptake, accurately reflecting the soil's nutrient supply capacity. This method exhibits good reproducibility and high precision, filling the technological gap in soil available strontium extraction and simultaneous multi-element detection, and providing reliable support for agricultural applications.

[0028] The advantages or beneficial effects of the extractant for extracting effective elements from soil and the detection method thereof of the present invention include at least the following:

[0029] The extraction agent and detection method of this invention achieve efficient and simultaneous extraction and detection of strontium, calcium, magnesium, and potassium in soil through the synergistic effect of multiple components such as acetic acid, ammonium fluoride, and amino acid ionic liquid. This method significantly improves the extraction efficiency of strontium, and the extracted strontium content shows a highly significant positive correlation with the strontium content in maize kernels, with R²=0.861 and P<0.01, accurately reflecting the soil's nutrient supply capacity to crops. It also boasts high precision, with RSDs of calcium, magnesium, and potassium <3% and strontium RSD of 1.39%-2.54%. Furthermore, it is simple to operate, avoiding the cumbersome procedures of traditional single-element determination using atomic absorption spectrometry. This technology successfully fills the gap in the lack of standardized detection methods for extracted strontium in soil, effectively solving problems such as incomplete element coverage, insufficient simultaneous multi-element detection, and complex procedures in existing methods. It provides a reliable and efficient scientific basis for the development of strontium-enriched functional agriculture, precise assessment of soil fertility, and safe planting of agricultural products. Detailed Implementation

[0030] To more clearly illustrate the purpose, technical solution, and advantages of this invention, the technical solution of this invention will be described in detail below through specific embodiments. It should be noted that these embodiments are only for illustrating this invention and not for limiting its scope of protection; the actual scope of protection of this invention should be determined by the claims.

[0031] Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available. Unless otherwise specified, the amount of each component in the following examples is 1 g per part by weight.

[0032] I. Implementation Examples

[0033] 1. Preparation of extractant A1: Dissolve 12.01 g acetic acid, 20.01 g ammonium nitrate, and 0.556 g ammonium fluoride in an appropriate amount of deionized water. Add 2.543 g aspartic acid hydrochloride, 19.21 g citric acid, and 3.43 g cocamidopropyl betaine. Stir at 30℃ and 400 r / min for 60 min until completely dissolved. Make up to 1 L with deionized water. The resulting extractant is 0.2 mol / L acetic acid, 0.25 mol / L ammonium nitrate, 0.015 mol / L ammonium fluoride, 0.015 mol / L aspartic acid hydrochloride, 0.1 mol / L citric acid, 0.01 mol / L cocamidopropyl betaine, with the remainder being deionized water. This extractant is denoted as extractant A1.

[0034] Preparation of extractant A2: Dissolve 12.01 g acetic acid, 16.02 g ammonium nitrate, and 0.741 g ammonium fluoride in an appropriate amount of deionized water. Add 1.673 g glycine hydrochloride, 6.304 g citric acid, and 2.50 g dodecyl dimethyl betaine. Stir at 30℃ and 400 r / min for 60 min until completely dissolved. Make up to 1 L with deionized water and set aside. The resulting extractant is composed of 0.2 mol / L acetic acid, 0.2 mol / L ammonium nitrate, 0.02 mol / L ammonium fluoride, 0.015 mol / L glycine hydrochloride, 0.03 mol / L citric acid, 0.01 mol / L dodecyl dimethyl betaine, and the remainder is deionized water. This extractant is denoted as extractant A2.

[0035] Preparation of extractant A3: Dissolve 18.02 g acetic acid, 32.02 g ammonium nitrate, and 1.112 g ammonium fluoride in an appropriate amount of deionized water. Add 2.225 g alanine nitrate, 23.04 g citric acid, and 3.06 g dodecyl hydroxypropyl sulfobetaine. Stir at 30℃ and 400 r / min for 60 min until completely dissolved. Make up to 1 L with deionized water and set aside. The resulting extractant is composed of 0.3 mol / L acetic acid, 0.4 mol / L ammonium nitrate, 0.03 mol / L ammonium fluoride, 0.02 mol / L alanine nitrate, 0.12 mol / L citric acid, 0.0085 mol / L dodecyl hydroxypropyl sulfobetaine, and the remainder is deionized water. This extractant is denoted as extractant A3.

[0036] Preparation of extractant B: The difference from extractant A1 is that deionized water is used instead of aspartic acid hydrochloride, while the other raw material composition and process parameters are the same.

[0037] Preparation of extractant C: The difference between extractant C and extractant A1 is that deionized water is used instead of citric acid, while the other raw material composition and process parameters are the same.

[0038] Preparation of extractant D: The difference between extractant D and extractant A1 is that deionized water is used instead of biosurfactant (cocamidopropyl betaine), while the other raw material composition and process parameters are the same.

[0039] Preparation of extractant E: The difference between extractant E and extractant A1 is that equimolar amounts of nitric acid are used instead of aspartic acid hydrochloride and citric acid, while the composition of other raw materials and process parameters are the same.

[0040] M3 extractant: Its formula is 0.2 mol / L acetic acid, 0.015 mol / L ammonium fluoride, 0.013 mol / L nitric acid, 0.001 mol / L ethylenediaminetetraacetic acid, 0.25 mol / L ammonium nitrate, with the balance being deionized water.

[0041] 2. Soil sample processing: After collecting soil samples, spread them out flat and let them air dry naturally in a cool environment. Separate impurities during the air drying process, and then pass them through a 0.2mm sieve for later use.

[0042] 3. The method for detecting available elements in soil extracted from soil includes the following steps:

[0043] S1. Extraction operation: Weigh 10g of soil sample and place it in a dry stoppered extraction bottle. Add 120g of extraction agent and maintain a solid-liquid ratio of 1:12. Tighten the stopper and shake for 30min at 25℃±1℃ and 180r / min. Filter immediately and collect the filtrate. Complete the detection within 24h.

[0044] S2. Standard Curve Plotting: Using a multi-element standard solution of Sr, Ca, Mg, and K as the extraction medium, prepare a series of working standard solutions with concentrations of 0.00 mg / L, 0.50 mg / L, 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, and 10.00 mg / L. Start the ICP-OES instrument and set the parameters (emission power 1150W, cooling gas flow rate 13.5 L / min, auxiliary gas flow rate 1.0 L / min, nebulizing gas flow rate 1.0 L / min, sample rinsing time 15 s, analytical pump speed 50 rpm, rinsing pump speed 50 rpm, optical chamber temperature 38℃, camera temperature -). Preheat and stabilize at 40℃ (argon as carrier gas) for 30 min; determine the emission intensity of the standard working solution sequentially from low to high concentration, and plot the standard curve with elemental mass concentration as the abscissa and emission intensity as the ordinate. The analytical spectral wavelengths of Sr, Ca, Mg, and K are 407.7 nm, 317.9 nm, 285.2 nm, and 766.4 nm, respectively; the sampling points and concentration range of the standard curve can be adjusted according to the concentration of the analyte in the actual sample, and the standard curve is automatically plotted and stored by computer software.

[0045] S3. Sample testing: According to the instrument parameters mentioned above, determine the emission intensity of the blank solution and the sample filtrate, and substitute them into the standard curve to obtain the element concentration value; if the concentration exceeds the range of the standard curve, dilute with an extractant before testing.

[0046] S4. Sample testing: Substitute the obtained concentration values ​​into the formula to calculate the content of available Sr, Ca, Mg, and K in the soil sample.

[0047]

[0048] w - the mass fraction of the analyte in the sample, expressed in milligrams per kilogram (mg / kg).

[0049] ρ - The mass concentration of the element in the sample solution, expressed in micrograms per liter (mg / L).

[0050] ρ0 - The mass concentration of the element in the blank sample solution, in micrograms per liter (mg / L).

[0051] V - The final volume of the sample solution, in milliliters (mL).

[0052] f - Sample dilution factor;

[0053] m - The mass of the sample is measured in grams (g).

[0054] II. Performance Testing

[0055] 1. Comparison of extraction effects of different extractants

[0056] The effective elements in the soil used for growing pakchoi were tested using extractants A1-A3, BE, and M3 from examples. The soil had a pH of 6.5, organic matter of 2.3%, and CEC of 9.6 cmol / kg. The test results are shown in Table 1.

[0057] Table 1. Results of extraction effects of different extractants (n=6, mean ± standard deviation)

[0058]

[0059] Results Analysis: Table 1 shows that the extractants A1-A3 of this invention can simultaneously extract available Sr, Ca, Mg, and K, and the extraction efficiency for Sr is significantly higher than that of extractants BE and M3. Furthermore, the standard deviations of each element's content are small, indicating stable extraction effects and good reproducibility. The main manifestations of the decreased extractability of Sr by extractants BE and M3 are as follows:

[0060] Extraction agent B lacked an amino acid ionic liquid, and extraction agent C omitted citric acid, resulting in the disruption of the dual chelation system. Relying solely on amino acid ionic liquid or citric acid for chelation was insufficient to effectively stabilize the desorbed Sr, Ca, Mg, and other metal ions, making them prone to re-adsorption or precipitation. Furthermore, the lack of citric acid's auxiliary pH buffering function led to reduced ion exchange efficiency, decreased extraction yield, and poorer reproducibility. Extraction agent B's extraction efficiency for available strontium was only 0.15 ± 0.03 mg / kg, only 39.5% of that of extraction agent A1; extraction agent C's extraction efficiency for Sr was also only 47.4% of that of extraction agent A1, with an increased standard deviation.

[0061] In the absence of biosurfactants, the extract of extract D has insufficient wetting, dispersion and migration capabilities, soil particles aggregate and metal-chelates in micropores are difficult to release, desorbed ions are prone to re-adsorption, resulting in decreased extraction efficiency and affecting the uniformity and reproducibility of the system. The Sr extraction yield of extractant D is 0.21±0.04 mg / kg, which is 55.3% of that of extractant A1.

[0062] The Sr extraction efficiency of extractant E was only 0.12±0.03 mg / kg. This may be because extractant E uses nitric acid instead of amino acid ionic liquid. Its strong acidity not only destroys the suitable pH environment and inhibits the complexation of ammonium fluoride, but also lacks the chelating function of amino acids, resulting in local damage to soil structure, re-adsorption or precipitation of target ions, the lowest extraction efficiency and the system is extremely unstable.

[0063] Because the M3 extractant does not contain amino acid ionic liquids and biosurfactants, it lacks dual chelation and dispersion migration functions. At the same time, its chelating agent, ethylenediaminetetraacetic acid, has weak selectivity for Sr and a low concentration. In addition, the introduction of nitric acid leads to a low pH, resulting in insufficient overall synergistic effect. Therefore, its Sr extraction performance is generally lower than that of the extractant A1-A3 system.

[0064] 2. Precision test

[0065] Experimental design: Three soil samples with low, medium and high concentrations (numbered J1, J2 and J3) were selected. Pretreatment and detection were carried out using extractant A1 according to the soil sample treatment steps. Each sample was measured in parallel 6 times.

[0066] Basic physicochemical properties of the sample:

[0067] J1: Acidic sandy soil, pH 5.2, organic matter 1.8%, CEC 8.5 cmol / kg;

[0068] J2: Neutral farmland soil, pH 6.8, organic matter 2.5%, CEC 12.3 cmol / kg;

[0069] J3: Strontium-rich farmland soil, pH 7.8, organic matter 3.1%, CEC 15.7 cmol / kg.

[0070] Calculation results: Calculate the average value and relative standard deviation (RSD) of the 6 parallel test results.

[0071] Table 2 Precision test results (n=6)

[0072]

[0073] Results Analysis: As shown in Table 2, the relative standard deviation (RSD) of the extractant of this invention for low, medium, and high concentration samples is less than 3%, with the RSD for Sr being 1.39%-2.54%, and the RSDs for Ca, Mg, and K being less than 1.3%. This indicates that the extractant has good parallelism and high precision for the extraction of Sr, Ca, Mg, and K, and can meet the accuracy requirements for the detection of effective elements Sr, Ca, Mg, and K in soils with different properties.

[0074] 3. Test results of actual soil samples

[0075] Experimental Design: A total of 20 soil samples were collected from a strontium-rich agricultural product planting base (10 samples, numbered T1-T10) and ordinary farmland (10 samples, numbered T11-T20). The contents of available Sr, Ca, Mg, and K in the soil were determined according to the extraction agent and detection method in Example A1. At the same time, maize planted in the corresponding plots were collected as indicator crops, and the Sr content in maize kernels was determined. The correlation between soil-extractable Sr and plant-in vivo Sr was established. DPS statistical analysis software was used for regression analysis to calculate the correlation coefficient and significance level.

[0076] (1) Results of extractable element content determination of 20 actual soil samples

[0077] Table 3. Results of extractable Sr, Ca, Mg and K content determination in actual soil samples (n=6, mean ± standard deviation).

[0078]

[0079] (2) Correlation analysis between soil extractable Sr and plant Sr content

[0080] Table 4. Regression analysis results of soil extractable Sr (X1) and plant seed Sr (X2) content.

[0081]

[0082] The analysis based on the results in Table 3-4 is as follows:

[0083] First, the correlation analysis results showed that, regardless of whether it was strontium-rich soil, ordinary farmland, or all 20 samples, the extractable Sr content in the soil (X1) and the Sr content in plant grains (X2) were all significantly positively correlated (P < 0.01), with correlation coefficients R ranging from 0.915 to 0.932, and coefficients of determination R0.05. 2 All values ​​are greater than 0.83, indicating that the extractable Sr extracted by the extractant of this application can accurately reflect the absorption and utilization of Sr by plants, and the quantitative relationship between the two can be effectively described by a regression equation. Therefore, the extractable elements extracted by the extractant of this invention can truly reflect the soil's ability to supply nutrients to crops, and are suitable for practical applications such as soil fertility assessment and the suitability of safe planting of Sr-rich agricultural products.

[0084] Secondly, the regression equation X2 = 0.059 + 2.251X1 for the overall sample shows that for every 1 mg / kg increase in extractable Sr in the soil, the average Sr content in plant seeds increases by 2.251 mg / kg. This further verifies that the extractant has high selectivity and effectiveness in extracting extractable Sr, and can provide accurate soil Sr availability data for the suitability assessment of strontium-rich agricultural products.

[0085] Third, the detection reliability is good and meets the needs of practical applications. The detection results of 20 actual samples show that the relative deviation is less than 5%; combined with the relative standard deviation (RSD) of Sr element in the precision test, which is between 1.39% and 2.54%, it indicates that the extractant and detection method of the present invention have good stability, reproducibility and accuracy, and can meet the actual requirements of simultaneous detection of extracted Sr and Ca, Mg and K in soil.

[0086] It should be clarified that the above embodiments are merely illustrative of specific implementations of the present invention and do not constitute a limitation on the scope of protection of the present invention. Based on the technical content disclosed in this invention, those skilled in the art can make various modifications, adjustments, or equivalent substitutions within its basic principles and design concepts. These modifications and improvements need not be listed exhaustively, but should all be considered to fall within the scope of protection of this invention.

Claims

1. An extractant for extracting effective elements from soil, characterized in that, It includes the following components: 0.1-0.3 mol / L acetic acid, 0.1-0.4 mol / L ammonium nitrate, 0.01-0.03 mol / L ammonium fluoride, 0.01-0.02 mol / L amino acid ionic liquid, 0.03-0.12 mol / L citric acid, 0.005-0.02 mol / L biosurfactant, and the remainder is deionized water; The biosurfactant is at least one of cocamidopropyl betaine, dodecyl dimethyl betaine, and dodecyl hydroxypropyl sulfobetaine. The amino acid ionic liquid is at least one of aspartic acid hydrochloride, glycine hydrochloride, and alanine nitrate.

2. The extractant for extracting effective elements from soil as described in claim 1, characterized in that, The extractant for extracting effective elements from the soil consists of 0.2 mol / L acetic acid, 0.25 mol / L ammonium nitrate, 0.015 mol / L ammonium fluoride, 0.015 mol / L aspartic acid hydrochloride, 0.1 mol / L citric acid, 0.01 mol / L cocamidopropyl betaine, and the remainder being deionized water.

3. A method for preparing an extractant for extracting effective elements from soil according to claim 1, characterized in that, Includes the following steps: Dissolve acetic acid, ammonium nitrate, and ammonium fluoride in water, add amino acid ionic liquid, citric acid, and biosurfactant, stir until completely dissolved, and then bring the volume to the required level with deionized water.

4. The method for preparing the extractant for extracting effective elements from soil as described in claim 3, characterized in that, The stirring speed is 300-500 r / min, the temperature is 20-40℃, and the stirring time is 30-120 min.

5. An application of an extractant according to any one of claims 1-2 in soil testing, characterized in that, It is used for the simultaneous extraction of available strontium, calcium, magnesium and potassium from soil.

6. A method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using the extractant according to any one of claims 1-2, characterized in that, Includes the following steps: Weigh out the air-dried soil sample that has passed through a 0.2 mm sieve, add the extractant at a solid-liquid mass ratio of 1:10-15, and extract by shaking at 150-300 rpm for 10-60 minutes. Separate the solid and liquid, collect the filtrate, and determine the contents of strontium, calcium, magnesium, and potassium in the filtrate.

7. The method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using the extraction agent as described in claim 6, characterized in that, The temperature for the oscillation extraction is 20-40℃.

8. A method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using the extractant as described in any one of claims 6-7, characterized in that, The filtrate was tested using inductively coupled plasma atomic emission spectrometry.

9. The method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using the extraction agent as described in claim 8, characterized in that, The operating parameters of the inductively coupled plasma atomic emission spectrometer are as follows: emission power 1150W, cooling gas flow rate 13.5L / min, auxiliary gas flow rate 1.0L / min, nebulizing gas flow rate 1.0L / min, sample rinsing time 15s, analysis pump speed 50rpm, rinsing pump speed 50rpm, optical chamber temperature 38℃, detector cooling temperature -40℃, and carrier gas argon.

10. The method for simultaneous detection of available strontium, calcium, magnesium, and potassium in soil using the extractant as described in claim 8, characterized in that, The analytical spectral wavelengths for strontium, calcium, magnesium, and potassium were: strontium 407.7 nm, calcium 317.9 nm, magnesium 285.2 nm, and potassium 766.4 nm.

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