A method for the determination of multiple elements in soil or sediment by sodium carbonate fusion

Abstract

The application discloses a sodium carbonate alkali fusion method for measuring multiple elements in soil or sediment, and comprises the following steps: selecting anhydrous sodium carbonate as a flux, placing the flux and a to-be-measured object into a platinum gold crucible, moving the platinum gold crucible into a muffle furnace to heat, taking out the platinum gold crucible to shake and shape, placing the platinum gold crucible into room-temperature tap water to cool, adding deionized water, heating and pyrolyzing, soaking for 24 hours, fully stirring with a plastic rod, washing with deionized water, adding 2ml of dilute hydrochloric acid, heating at low temperature, crushing the fallen substances, stirring and adding nitric acid-hydrochloric acid mixed acid, dissolving and transferring, constant volume and uniform shaking, and after filtration, the obtained solution can be directly used for measuring boron elements, and after dilution with an appropriate multiple, the solution can be used for detecting other elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental detection, and in particular to a sodium carbonate alkali fusion method for determining multiple elements in soil or sediment. BACKGROUND

[0002] At present, the determination of inorganic elements in soil or sediment in China is mostly by atomic absorption method, and the pretreatment is mostly by acid fusion method, but the acid fusion method cannot determine the silicon element. The method of "determination of 11 elements in soil or sediment by alkali fusion-inductively coupled plasma atomic emission spectrometry" (HJ 974-2018) fills the blank of the determination of inorganic elements in soil or sediment by alkali fusion-inductively coupled plasma atomic emission spectrometry in China, but the flux used in this method is sodium carbonate, lithium tetraborate and lithium metaborate, the fusion product is dissolved with a mixture of hydrochloric acid and nitric acid, and the constant volume is 500 mL, and boron element cannot be determined at the same time. The research report on this method shows that, compared with sodium carbonate, lithium tetraborate and lithium metaborate, the sodium carbonate flux has no obvious difference in the determination results of other elements except the silicon element. The method of determining total boron in soil by alkali fusion-inductively coupled plasma atomic emission spectrometry mentioned in chapter 18.1 of "soil analysis technical specification" (second edition) uses sodium carbonate as flux, dilutes the fusion product with dilute sulfuric acid, and the constant volume is 100 mL. The two standards have some differences in the mixing method of flux, the duration and temperature of fusion, but the differences are not big, and the description of the process of dissolving the fusion product is too simple, which easily leads to the problems that the fusion product cannot be completely dissolved and the silicon is precipitated when dissolved during the verification experiment.

[0003] The platinum crucible used for alkali fusion is expensive and rare in quantity, and if the silicon and boron elements can be determined at the same time as the determination of multiple metal elements by one pretreatment, the detection efficiency can be greatly improved, and the manpower and material resources can be saved, so the project group establishes to conduct in-depth research, integration and improvement on the two standards.

[0004] Therefore, a technical means is provided, sodium carbonate is selected as flux, and a method is designed to determine metal elements in soil or sediment, which can determine silicon, boron and other elements while ensuring precision and accuracy, so that more than ten elements can be determined at the same time by one alkali fusion pretreatment of the sample, which greatly improves the detection efficiency and saves time and labor cost. SUMMARY

[0005] The present application relates to the technical field of environmental detection, and in particular to a sodium carbonate alkali fusion method for determining multiple elements in soil or sediment.

[0006] The present application provides a sodium carbonate alkali fusion method for determining multiple elements in soil or sediment, which comprises a fusion extraction method of multiple elements in soil or sediment.

[0007] a. Place anhydrous sodium carbonate flux at the bottom of the crucible;

[0008] b. Place the soil or sediment sample to be tested evenly on anhydrous sodium carbonate flux;

[0009] c. Add anhydrous sodium carbonate on top of the sample layer;

[0010] d. Cover the entire mixture with another layer of anhydrous sodium carbonate flux.

[0011] Furthermore, the soil or sediment samples to be tested are processed by foreign matter removal, air drying, grinding, and passing through a nylon sieve;

[0012] Preferably, the nylon sieve aperture is 0.096 mm.

[0013] Furthermore, the method for molten extraction of elements from soil or sediments also includes the step of placing a crucible in a muffle furnace, heating it to 1000°C, maintaining it for 30 minutes, and then removing it.

[0014] Furthermore, after removing the crucible, while the sample is still in a molten state, remove the lid and place it in cold water. Then, rotate the crucible at a constant speed to allow the molten liquid to gradually solidify into a thin layer at the bottom and 1 / 3 of the crucible wall.

[0015] Furthermore, the process includes cooling the bottom of the crucible in room temperature tap water until slight cracks appear, then adding about half the volume of deionized water to the crucible, heating and pyrolyzing at 90°C, soaking overnight for 24 hours, and stirring thoroughly with a plastic rod to remove as much of the molten material as possible from the crucible.

[0016] Furthermore, by weight, 0.4 parts by weight of the anhydrous sodium carbonate flux are placed at the bottom of the crucible, 0.2 parts by weight of the soil or sediment sample to be tested are evenly placed on the anhydrous sodium carbonate flux, 0.6 parts by weight of anhydrous sodium carbonate are added on the sample layer, and then a layer of 0.4 parts by weight of anhydrous sodium carbonate flux is covered.

[0017] Preferably, the crucible is a platinum crucible.

[0018] Furthermore, the grinding step is carried out in a ball mill or a mortar;

[0019] Furthermore, this includes methods for determining the content of multiple elements in soil or sediments, which include the following steps:

[0020] a. Dissolve the melt obtained by the melt extraction method according to any one of claims 3 to 7 and transfer it to a volumetric flask and bring it to volume;

[0021] b. After filtration, it can be used directly for boron determination;

[0022] c. Dilute it 50 times and use it to determine silicon content;

[0023] d. For other elements, the preliminary concentration range of the element is determined by the inductively coupled plasma atomic emission spectrometer (ICP-AES). The dilution factor of the melt is adjusted according to the preliminary determination results so that the concentration of the element falls within the linear detection range of the instrument. Then the content of the element is re-determined and the results are recorded.

[0024] Furthermore, in step d of the method for determining the content of multiple elements in soil or sediment, the dilution factor can be adjusted according to the specific concentration of the element to be measured and the detection sensitivity of the instrument.

[0025] Furthermore, the method for determining the content of multiple elements in soil or sediments also includes the step of adding dilute hydrochloric acid and a nitric acid-hydrochloric acid mixture during the dissolution process of the melt to promote the complete dissolution of the melt;

[0026] Preferably, the volume ratio of nitric acid to hydrochloric acid in the nitric acid-hydrochloric acid mixed acid is 1:4.

[0027] The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments proposed in this invention has the following beneficial effects:

[0028] 1. Using sodium carbonate as a flux, it is possible to simultaneously determine elements such as silicon and boron, allowing for the simultaneous determination of more than ten elements after a single alkaline fusion pretreatment of the sample.

[0029] 2. While ensuring precision and accuracy, it greatly improves detection efficiency. The preparation method is simple and easy to operate, making it suitable for large-scale industrial production.

[0030] 3. Anhydrous sodium carbonate is a commonly used alkali flux that can effectively decompose silicates and other refractory compounds in soil or sediments, promote chemical reactions during the melting process, and improve element extraction efficiency. It enables the efficient extraction of multiple elements from soil or sediments. A novel combination and ratio of raw materials is used, and by optimizing the proportion of each component and the preparation process, efficient and accurate determination of multiple elements in soil or sediments is achieved, significantly improving element extraction efficiency and reducing errors and interferences in the determination process. It is suitable for various types of soil or sediment samples, including refractory samples with high silicon, high aluminum, and high calcium content. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component content, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. Unless otherwise specified, the experimental materials used in the following examples are all purchased from commercial channels.

[0033] The materials mentioned in this invention were sourced from the following: soil samples were purchased.

[0034] Unless otherwise specified, all reagents should be used as is without further purification.

[0035] In the preparation examples and embodiments of the present invention, unless otherwise specified, "parts" refers to parts by weight, and unless otherwise specified, "concentration percentage" refers to weight concentration.

[0036] The parameters of the inductively coupled plasma atomic emission spectrometer used in the on-machine testing of this invention are as follows: plasma gas flow rate 20 L / min; auxiliary gas flow rate 0.5 L / min; nebulizer flow rate 0.8 L / min; sample injection volume 2.5 mL / min; power 1500 W; lamp current 30 mA; carrier gas flow rate 400 mL / min; shielding gas flow rate 800 mL / min; and detection wavelength selected as 254.1 nm.

[0037] Example 1

[0038] The soil or sediment samples to be tested were treated by foreign matter removal, air drying, grinding, and sieving through a 0.096 mm nylon sieve. 0.4 parts by weight of anhydrous sodium carbonate flux was placed at the bottom of a platinum crucible. 0.2 parts by weight of the soil or sediment sample to be tested was then evenly placed on top of the anhydrous sodium carbonate flux. The main purpose of this layer was to allow the sample to initially contact the flux, preparing for the subsequent melting reaction. A layer of 0.6 parts by weight of anhydrous sodium carbonate was then added on top of the sample layer. This layer promoted complete melting of the sample and ensured that all elements were effectively extracted. Finally, a layer of 0.4 parts by weight of anhydrous sodium carbonate flux was placed on top of the entire mixture. The main purpose of this layer was to prevent the evaporation of the sample and solvent during the melting process and also to help maintain the stability of the molten state.

[0039] Cover the crucible and place it in a muffle furnace. Heat to 1000℃ and maintain for 30 minutes. Stop heating and remove the crucible after 5 minutes. While the sample is still molten, remove the lid and place it in cold water. Then, rotate the crucible at a constant speed to allow the molten liquid to gradually solidify into a thin layer at the bottom and 1 / 3 of the wall. Cool the bottom of the crucible in room temperature tap water until slight cracks appear. Add 1 / 2 crucible volume of deionized water and heat at 90℃ for pyrolysis. Soak overnight for 24 hours, stirring thoroughly with a plastic rod to remove as much of the molten material as possible from the crucible. Pour the mixture into a plastic beaker and rinse 1-2 times with a small amount of deionized water. Add 2 ml of dilute hydrochloric acid dropwise along the crucible wall and heat at a low temperature to dissolve the remaining molten material. Break up any large molten material in the beaker with a plastic rod. Using a dropper or pipette, quickly add 10 ml of a 1+4 nitric acid-hydrochloric acid mixture while stirring / shaking. This process will generate numerous bubbles. The molten material will dissolve completely, slowly turning into a yellow, transparent liquid. Repeat this process several times. After the molten material is completely dissolved, transfer it to a 100 ml plastic volumetric flask, dilute to volume, shake well, and filter. This solution can be used directly for boron determination. Diluting it 50 times allows for silicon determination. For other elements, a preliminary determination of the solution can be performed using an inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the approximate concentration range of the element. Based on the preliminary results, adjust the dilution factor of the molten material to ensure the element concentration falls within the instrument's linear detection range before re-determining the element's content and recording the results.

[0040] Furthermore, when the crucible is placed in a muffle furnace and heated to 1000℃, the target temperature is controlled within the muffle furnace using 1000℃ as the target temperature. This includes: dividing the target temperature into multiple temperature gradients according to a preset gradient rule; after placing the crucible lid in the muffle furnace, controlling the temperature rise according to the first gradient heating rate; adjusting the heating control according to the second gradient heating rate when the overall crucible temperature reaches the first temperature gradient; continuing to adjust the heating control according to the third gradient heating rate; and repeating this cycle multiple times until the overall crucible temperature reaches the target temperature. After the overall crucible temperature reaches the target temperature, the heating control is then adjusted to maintain a constant temperature. In the preset gradient rule, the temperature difference of each temperature gradient is an increasing sequence, and the heating rate of each gradient is also increasing. The above technical solution enables the muffle furnace to gradually control the target temperature during the heating process by performing gradient segmentation according to a preset gradient rule, thus avoiding uneven heating of the crucible due to excessively rapid temperature changes and damage to the crucible.

[0041] Furthermore, the plastic stirring rod is equipped with multiple stirring blades, and an intelligent control system is configured for the plastic stirring rod. When the plastic stirring rod is used for thorough stirring, the stirring blades are merged according to a start signal. Then, based on the merged stirring blades, stirring is performed according to a first preset power and a first preset time. When the stirring time reaches the first preset time, the first stirring mode is completed. At this point, the merged stirring blades are separated, allowing them to return to their initial state. Then, a second stirring is performed according to a second preset power and a second preset time, until the second stirring time reaches the second preset time, completing the second stirring. The first preset power is greater than the second preset power, and the first and second preset times can be the same or different. The above technical solution achieves intelligent stirring of the plastic stirring rod through an intelligent control system, which not only saves manpower and enables rapid stirring but also ensures stirring effect, allowing more molten material to detach from the crucible. By dividing the stirring process into two stages, the molten material adhering to the crucible can be better removed, ensuring the molten material can be removed from the pot, improving stirring efficiency, and providing convenience for the subsequent use of the molten material. Moreover, based on the combined stirring blades, stirring according to the first preset power and the first preset time, not only can the molten material with strong adhesion to the crucible be removed, avoiding damage to the plastic stirring rod, but also large areas of molten material can be removed from the pot simultaneously, improving the removal efficiency. By continuing to stir according to the second preset power and the second preset time, smaller residual molten material on the crucible can be removed, allowing more molten material to be removed from the pot as much as possible, ensuring the stirring effect.

[0042] Performance testing

[0043] The standard test samples with known element contents were tested using Example 1, and the results are shown in Table 1.

[0044] Table 1

[0045]

[0046]

[0047] As shown in Table 1, the calculated results obtained using Example 1 show a small deviation from the actual true values ​​of the content of each element.

[0048] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A method for determining multiple elements in soil or sediment using sodium carbonate alkali fusion, characterized in that, A melting extraction method for multiple elements in soil or sediments, comprising the following steps: a. Place anhydrous sodium carbonate flux at the bottom of the crucible; b. Place the soil or sediment sample to be tested evenly on anhydrous sodium carbonate flux; c. Add anhydrous sodium carbonate on top of the sample layer; d. Cover the entire mixture with another layer of anhydrous sodium carbonate flux; Place 0.4 parts by weight of anhydrous sodium carbonate flux at the bottom of the platinum crucible. Then, evenly place 0.2 parts by weight of the soil or sediment sample to be tested on the anhydrous sodium carbonate flux. The main purpose of this layer is to allow the sample to initially contact the flux, preparing for the subsequent melting reaction. Next, add another layer of 0.6 parts by weight of anhydrous sodium carbonate on top of the sample layer. This layer promotes complete melting of the sample and ensures that all elements are effectively extracted. Finally, cover the entire mixture with another 0.4 parts by weight of anhydrous sodium carbonate flux. This layer prevents the evaporation of the sample and solvent during the melting process and also helps maintain the stability of the molten state. The melt obtained by the melt extraction method is dissolved and transferred to a volumetric flask and brought to volume; after filtration, it is used directly for boron determination.

2. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 1, characterized in that, The soil or sediment samples to be tested are subjected to foreign matter removal, air drying, grinding, and sieve treatment with a nylon sieve aperture of 0.096 mm.

3. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 1, characterized in that, It also includes placing the crucible in a muffle furnace and heating it to 1000°C, holding it for 30 minutes, and then removing the crucible.

4. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 3, characterized in that, After removing the crucible, while the sample is still molten, remove the lid and place it in cold water. Shake the crucible in a circular motion to allow the molten liquid to gradually solidify into a thin layer at the bottom and 1 / 3 of the crucible wall.

5. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 4, characterized in that, It also includes cooling the bottom of the crucible in room temperature tap water until slight cracks appear, then adding 1 / 2 the volume of deionized water to the crucible, heating and pyrolyzing at 90°C, soaking overnight for 24 hours, and stirring with a plastic rod.

6. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 2, characterized in that, The grinding step is carried out in a ball mill or mortar.

7. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 1, characterized in that, This includes methods for determining the content of multiple elements in soil or sediments, and these methods include the following steps: a. Dissolve the melt obtained by the melt extraction method according to any one of claims 3 to 6 and transfer it to a volumetric flask and bring it to volume; b. After filtration, it can be used directly for boron determination; c. Dilute it 50 times and use it to determine the silicon element; d. For other elements, the concentration range of the element is determined by preliminary determination of the test solution using inductively coupled plasma atomic emission spectrometry. The dilution factor of the melt is then adjusted according to the preliminary determination results to make the concentration of the element fall within the linear detection range of the instrument. The content of the element is then re-determined and the results are recorded.

8. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 7, characterized in that, In step d of the method for determining the content of multiple elements in soil or sediment, the dilution factor can be adjusted according to the specific concentration of the element to be measured and the detection sensitivity of the instrument.

9. The sodium carbonate alkali fusion method for determining multiple elements in soil or sediments according to claim 7, characterized in that, The method for determining the content of multiple elements in soil or sediments further includes the step of adding dilute hydrochloric acid and a nitric acid-hydrochloric acid mixture during the dissolution of the melt to promote complete dissolution of the melt, wherein the volume ratio of nitric acid to hydrochloric acid in the nitric acid-hydrochloric acid mixture is 1:4.

Images