A method for efficient extraction and detection of soil chloride ions suitable for continuous flow method

Abstract

The present invention provides a soil chloride ion efficient extraction and detection method suitable for continuous flow method, the method comprising extract preparation, sample pretreatment and determination. The extraction and detection method of the present invention has a high extraction rate for chloride ions, can accurately reflect the true chloride ion content in the soil, and the average value of the chlorine content is 0.59-0.71% and the standard value deviation is 0.59-0.71%, and the blank spike recovery rate is 100.2-100.7%; the extraction and detection method of the present invention has high precision, and the precision test RSD is 0.40-0.45%; the extraction and detection method of the present invention has high accuracy, and the accuracy test RSD is 0.48-0.52%.

Description

Technical Field

[0001] The invention relates to a soil chloride ion efficient extraction and detection method suitable for a continuous flow method, and belongs to the field of quantitative detection. Background Art

[0002] NY / T1121.17-2006, in soil testing, Part 17 discloses a method for determining soil chloride ion content, which uses carbon dioxide-free distilled water for extraction and then titrates with a standard silver nitrate solution to determine the chloride content in the soil. This method is too simple, the water extraction rate for chloride ions is low, the manual titration endpoint observation is inaccurate, the measurement error is large, and it cannot reflect the actual chloride ion content in the soil.

[0003] In the determination of soil chloride ion content in NY / T1378-2007, water is also used to extract the soil, and the chloride ion content of the extract is determined using potentiometric titration or manual silver nitrate titration. The potentiometric titrator can accurately determine the end point, but water extraction also has a low chloride ion extraction rate and a large measurement error, and cannot reflect the actual chloride ion content in the soil.

[0004] The article "Determination of Chlorine in Tobacco-Growing Soil by Continuous Flow Method" was published in the 3rd issue of "Tobacco Science and Technology" in 2012 (article number 1002-0861 (2012) 03-0064-03). The chloride ions in the soil were extracted with water and determined by the continuous flow method. The spiked recovery rate after extraction was high, indicating that the extraction effect of chlorine in the soil was poor. In addition, the soil sample had to be extracted and the extract was filtered to obtain the test solution. The above method was time-consuming and complicated, and the filtration step could not be replaced by conventional filtration. The extract was a suspension after shaking, and conventional filter paper could not obtain a clear test solution.

[0005] CN108956815B discloses a method for testing the chloride ion content in sea sand, which comprises extraction by distillation after ultrasonic treatment. The steps are relatively complicated and different types of acids need to be used for elution. Although the amount of chloride ion extraction can be increased, the cost is relatively high.

[0006] In summary, the existing technical solutions have the following deficiencies:

[0007] (1) The existing method with simple steps has a low extraction rate of chloride ions and cannot accurately reflect the actual chloride ion content in the soil;

[0008] (2) The existing methods with high extraction rates have complicated steps and high costs. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention improves the leaching solution, mixes and grinds the sample with modified silicon dioxide particles, and provides a method for efficiently extracting soil chloride ions suitable for a continuous flow method, thereby solving the following technical problems:

[0010] (1) The extraction rate of chloride ions is high and can accurately reflect the actual chloride ion content in the soil;

[0011] (2) The steps are simple and the cost is low.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] The invention discloses a soil chloride ion efficient extraction and detection method applicable to a continuous flow method, which comprises extract preparation, sample pretreatment and determination.

[0014] The following are further improvements to the above technical solution:

[0015] The extract preparation includes preparing the extract with potassium sulfate or preparing the extract with potassium sulfate and modified lignin powder;

[0016] The potassium sulfate extract is prepared by adding deionized water to potassium sulfate and dissolving it by ultrasonication to obtain the potassium sulfate extract;

[0017] The concentration of potassium sulfate in the potassium sulfate extract is 0.08-0.12 mol / L.

[0018] The potassium sulfate and modified lignin powder are used to prepare an extract, the potassium sulfate is dissolved in deionized water, and the modified lignin powder is added and dispersed by ultrasonic to obtain a potassium sulfate extract;

[0019] The concentration of potassium sulfate in the potassium sulfate extract is 0.08-0.12 mol / L;

[0020] The concentration of the modified lignin powder is 1.8-2.2 g / L.

[0021] The sample pretreatment includes direct leaching or mixing and leaching;

[0022] The direct extraction is to weigh a soil sample that has passed through a 1.5-2.5 mm sieve and mix it with the extract, then shake it at 160-200 rpm for 25-35 min, let it stand for 5-7 min, filter the supernatant and discard the first 4-6 mL to obtain the extract;

[0023] The mass volume ratio of the sample to the extract is 1 g:4.5-5.5 mL.

[0024] The mixing comprises weighing a soil sample having a sieve hole of 1.5-2.5 mm and mixing it with the modified silicon dioxide particles, grinding the mixture, and mixing the mixture with the leaching solution after grinding to obtain the leaching solution.

[0025] The mass ratio of the soil sample to the modified silica particles is 4.5-5.5:1;

[0026] The mass volume ratio of the sample to the extract is 1 g:4.5-5.5 mL.

[0027] The preparation method of the modified silicon dioxide particles comprises the following steps: melting and blending 80-120 mesh graphite particles and paraffin wax at 75-85° C. for 50-70 minutes and then cooling, adding silica sol with a mass concentration of 30-40%, stirring at 40-50° C. for 50-70 minutes, airflow drying, and then calcining at 480-520° C. for 130-170 minutes, and crushing to 130-170 mesh to obtain modified silicon dioxide particles;

[0028] The mass ratio of graphite particles to paraffin is 2.5-3.5:1;

[0029] The mass ratio of the silica sol to the graphite particles is 4.5-5.5:1.

[0030] For the extraction, the extract is ultrasonicated at a power of 90-110 W for 8-12 minutes, then heated and boiled for 2-4 minutes, and then oscillated at a frequency of 180-200 rpm for 25-35 minutes. After the extraction, the extract is allowed to stand for 5-7 minutes, and the supernatant is filtered and the first 4-6 mL is discarded to obtain an extract.

[0031] The determination, content determination and calculation methods adopt the method of YC / T 162-2011, wherein the reagents and materials used in step 4 are all analytically pure, wherein the sample preparation and sample treatment in step 6 are replaced by the extract preparation step and sample pretreatment step in this embodiment, and the extract is measured.

[0032] Compared with the prior art, the present invention achieves the following beneficial effects:

[0033] The extraction and detection method of the present invention has a high extraction rate for chloride ions and can accurately reflect the true chloride ion content in the soil. The deviation between the average value of the measured chloride content and the standard value is 0.59-0.71%, and the blank spike recovery rate is 100.2-100.7%;

[0034] The extraction and detection method of the present invention has high precision, and the RSD of the precision test is 0.40-0.45%;

[0035] The extraction and detection method of the present invention has high accuracy, and the RSD of the accuracy test is 0.48-0.52%;

[0036] The extraction and detection method of the invention has simple steps and low cost. DETAILED DESCRIPTION

[0037] Example 1

[0038] (1) Extract preparation

[0039] Accurately weigh 17.5 g of potassium sulfate (analytical grade) into a beaker, add deionized water to dissolve, and dilute to 1 L to obtain potassium sulfate extract;

[0040] The extract was ultrasonically treated for 5 min to remove dissolved gas in water;

[0041] (2) Sample pretreatment

[0042] Direct extraction

[0043] Accurately weigh 5 g (accurate to 0.01 g) of air-dried soil sample that has passed through a 2 mm sieve, place it in a 100 mL conical flask, and accurately add 25 mL (accurate to 0.01 mL) of extract;

[0044] Place the conical flask on a shaker and oscillate at 180 rpm for 30 min. Take it out after the shaking and let it stand for 6 min. The layers will be clearly separated. Filter the supernatant with medium-speed qualitative filter paper and discard the first 5 mL to obtain a clear extract for testing.

[0045] (3) Determination

[0046] The method for determining and calculating the chlorine content adopts the method of YC / T 162-2011, wherein the reagents and materials used in step 4 are all analytically pure, and the sample preparation and sample treatment in step 6 are replaced by the extract preparation in step (1) and the sample pretreatment in step (2) in this embodiment, and the extract is measured.

[0047] Example 2

[0048] (1) Extract preparation

[0049] Accurately weigh 17.5 g of potassium sulfate (analytical grade) and dissolve it in deionized water, then add and disperse 2 g of modified lignin powder, mix and adjust the volume to 1 L to obtain an extract;

[0050] After the preparation is completed, the extract is ultrasonically treated for 5 minutes to remove the gas dissolved in the water;

[0051] The preparation method of the modified lignin powder comprises drying the lignin at 60° C. until there is no moisture, putting the dried lignin into a reactor, introducing a mixed gas of ozone and air, maintaining the pressure at 1.2 MPa for 360 minutes, and releasing the pressure after the reaction is completed to obtain the modified lignin powder;

[0052] The mass ratio of ozone to air in the ozone-air mixed gas is 1:3.

[0053] (2) Sample pretreatment

[0054] a. Mixing

[0055] Accurately weigh 5 g (accurate to 0.01 g) of air-dried soil sample that has passed through a 2 mm sieve, mix and grind it with 1 g (accurate to 0.01 g) of modified silica particles, put it into a 100 mL conical flask after grinding, and accurately add 25 mL (accurate to 0.01 mL) of leaching solution to obtain the leaching solution;

[0056] The preparation method of the modified silicon dioxide particles comprises the following steps: melting and blending 100-mesh graphite particles and paraffin wax at 80° C. for 60 minutes and then cooling, adding silica sol with a mass concentration of 35%, stirring at 45° C. for 60 minutes, airflow drying, placing in a muffle furnace after drying, calcining at 500° C. for 150 minutes, and crushing to 150 mesh to obtain modified silicon dioxide particles;

[0057] The mass ratio of graphite particles to paraffin is 3:1;

[0058] The mass ratio of the silica sol to the graphite particles is 5:1.

[0059] b. Extraction

[0060] The flask was ultrasonicated at 100W for 10 minutes, then placed on an induction cooker, heated and boiled for 3 minutes, and then the flask was placed on a shaker and oscillated at 190 rpm for 30 minutes.

[0061] After shaking, take out the mixture and let it stand for 6 minutes until distinct stratification occurs.

[0062] Take the supernatant and filter it using medium-speed qualitative filter paper, discard the first 5 mL to obtain a clear extract for testing.

[0063] (3) Determination

[0064] The method for determining and calculating the chlorine content adopts the method of YC / T 162-2011, wherein the reagents and materials used in step 4 are all analytically pure, and the sample preparation and sample treatment in step 6 are replaced by the extract preparation in step (1) and the sample pretreatment in step (2) in this embodiment, and the extract is measured.

[0065] Comparative Example 1

[0066] On the basis of Example 1, the extract preparation step uses deionized water without adding any substance as the extract, and the remaining steps are the same as those in Example 1 for measurement.

[0067] Example 3 Precision Determination:

[0068] The test sample is chestnut soil standard material, the standard number is GBW07402a (GSS-2a), the chlorine standard value is 51 mg / kg, and the method of Example 1, Example 2, and Comparative Example 1 is used for detection. The extract is measured five times in parallel and the results are recorded and the relative standard deviation is calculated. The measurement results are shown in Table 1

[0069] Example 4 Accuracy Determination

[0070] The test sample is chestnut soil standard material, the standard material number is GBW07402a (GSS-2a), the chlorine standard value is 51 mg / kg, five soil component analysis standard materials are weighed and five extracts are prepared, and the methods of Example 1, Example 2 and Comparative Example 1 are used to detect the chlorine content and calculate the results. The results are shown in Table 2

[0071] Example 5 Blank spike recovery determination

[0072] The blank spike recovery determination method is as follows: the extracted sample after the accuracy determination in Example 4 is dried, 5 g (accurate to 0.01 g) is weighed and added with 25 ml of leaching solution respectively, and the leaching solution is added with a sodium chloride standard solution so that the sodium chloride concentration in the leaching solution is 100 μg / ml, 150 μg / ml, 200 μg / ml, 250 μg / ml, and 300 μg / ml respectively. After extraction, the methods of Example 1, Example 2, and Comparative Example 1 are used for detection, and the spike recovery is calculated. The determination results are shown in Table 3.

[0073] Table 1 Precision test (unit: mg / kg)

[0074]

[0075] Table 2 Accuracy test results (unit: mg / kg)

[0076]

[0077] Table 3 Results of spike recovery determination

[0078]

Claims

1. A soil chloride ion efficient extraction and detection method suitable for continuous flow method, characterized in that: The method comprises extract preparation, sample pretreatment and determination; The method for preparing the extract is to prepare the extract with potassium sulfate and modified lignin powder; The potassium sulfate and modified lignin powder are used to prepare an extract, the potassium sulfate is dissolved in deionized water, and the modified lignin powder is added and dispersed by ultrasonic to obtain a potassium sulfate extract; The concentration of potassium sulfate in the potassium sulfate extract is 0.08-0.12 mol / L; The modified lignin powder concentration is 1.8-2.2 g / L; The sample pretreatment includes mixing and leaching; The mixing comprises weighing a soil sample having a sieve hole of 1.5-2.5 mm and mixing it with the modified silicon dioxide particles and grinding the mixture, and then mixing the mixture with the extract to obtain the extract; The mass ratio of the soil sample to the modified silica particles is 4.5-5.5:1; The preparation method of the modified silicon dioxide particles comprises the following steps: melt-blending 80-120 mesh graphite particles and paraffin wax at 75-85° C. for 50-70 minutes and then cooling, adding silica sol with a mass concentration of 30-40%, stirring at 40-50° C. for 50-70 minutes, air flow drying, and then calcining at 480-520° C. for 130-170 minutes, and crushing to 130-170 mesh to obtain the modified silicon dioxide particles.

2. The method for efficient extraction and detection of soil chloride ions suitable for continuous flow method according to claim 1, characterized in that: The mass ratio of graphite particles to paraffin is 2.5-3.5:1; The mass ratio of the silica sol to the graphite particles is 4.5-5.5:

1.

3. The method for efficient extraction and detection of soil chloride ions suitable for continuous flow method according to claim 1, characterized in that: For the extraction, the extract is ultrasonicated at a power of 90-110 W for 8-12 minutes, then heated and boiled for 2-4 minutes, and then oscillated at a frequency of 180-200 rpm for 25-35 minutes. After the extraction, the extract is allowed to stand for 5-7 minutes, and the supernatant is filtered and the first 4-6 mL is discarded to obtain an extract.

4. The method for efficient extraction and detection of soil chloride ions suitable for continuous flow method according to claim 1, characterized in that: The determination, content determination and calculation methods adopt the method of YC / T 162-2011, wherein the reagents and materials used in step 4 are all analytically pure, wherein the sample preparation and sample treatment in step 6 are replaced by the extract preparation step and the sample pretreatment step, and the extract is determined.

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