Method for measuring trace tin in brine

Abstract

The invention belongs to the technical field of detection, and relates to a method for determining trace tin in brine, in particular to a method for determining trace tin in brine through ferric hydroxide coprecipitation-inductively coupled plasma spectrometry. The method comprises the following steps: adjusting the pH value of brine to 8-10, then adding ferric chloride, stirring for reaction, and collecting a solid product; dropwise adding a sulfuric acid solution into the solid product until the solid product is completely dissolved to obtain a solution to be detected; and measuring the tin content in the solution to be measured by using inductively coupled plasma spectrometry. According to the method, the influence of matrix salinity is eliminated, the detection limit is low, the sensitivity is high, the operation is simple, convenient and rapid, and the detection limit is (3s / N) = 0.37 mu g / mL.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, and more specifically relates to a method for determining trace tin in brine. Background Art

[0002] Tin is a silvery white metal with strong luster, high density, stable chemical properties, and non-toxic tin salts. It is widely used in life, industry and other fields. The content of tin in natural brine and salt water is low. If it is not enriched and separated, it cannot be directly measured by general quantitative methods. The mineralization of brine is usually greater than 50g / L. In some areas, the mineralization of brine is as high as 200-300g / L, which has serious matrix interference in the direct determination of trace tin. Therefore, how to provide a method for detecting trace tin in brine with low detection limit, high sensitivity, simple operation and rapidity has become a difficult problem that technicians in this field need to overcome. Summary of the invention

[0003] The purpose of the present invention is to provide a method for determining trace tin in brine, and more specifically, to provide a method for determining trace tin in brine by ferric hydroxide coprecipitation-inductively coupled plasma spectrometry, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention is to provide a method for determining trace tin in brine, the steps comprising:

[0006] The pH value of the brine is adjusted to 8-10, and then ferric chloride is added, and after stirring for reaction, the solid product is collected;

[0007] Add sulfuric acid solution dropwise to the solid product until it is completely dissolved to obtain a solution to be tested;

[0008] The tin content in the solution to be tested is determined by inductively coupled plasma spectroscopy.

[0009] Furthermore, the brine is chloride brine or sulfate brine.

[0010] Furthermore, the pH value is adjusted to 8-10 using a sodium hydroxide solution.

[0011] Optionally, the concentration of the sodium hydroxide solution is 0.5 mol / L.

[0012] Furthermore, the dosage ratio of the ferric chloride to the brine is 20 mg:250 mL.

[0013] pH value was adjusted to 8-10, Fe(OH) 3 The precipitation is complete; when pH is less than 8, Fe(OH) 3Incomplete generation affects the enrichment efficiency; when pH>10, the brine contains a large amount of Mg 2+ A large amount of Mg(OH) will be generated 2 The influence of Fe(OH) 3 Enrichment of trace tin.

[0014] Furthermore, the ferric chloride is added in the form of an aqueous solution with a concentration of 10 mg / mL.

[0015] Furthermore, the stirring reaction is carried out at a speed of 80-120 rpm and the reaction time is not less than 30 min.

[0016] Fe(OH) 3 It is insoluble in water, so the generated Fe(OH) 3 The precipitate cannot be evenly distributed in the brine solution for a long time, so it may happen that the tin is not fully enriched and the Fe(OH) 3 The precipitated Fe(OH) 3 The precipitate is suspended in the brine solution for a long time to allow the tin to be enriched as completely as possible.

[0017] Furthermore, the concentration of the sulfuric acid solution is 0.18 mol / L.

[0018] Furthermore, the step of determining the tin content in the solution to be tested by inductively coupled plasma spectroscopy includes:

[0019] By measuring the standard solution of tin, the linear relationship of tin in the range of 0-10 mg / L was obtained;

[0020] Then, the solution to be tested is measured, and the tin content in the solution to be tested is obtained based on the linear relationship of tin in the range of 0-10 mg / L.

[0021] Optionally, the concentration of iron ions in the standard tin solution is 80 mg / 100 mL.

[0022] Optionally, the concentration of tin in the standard tin solution is 0 mg / L, 0.25 mg / L, 0.5 mg / L, 1 mg / L, 3 mg / L, 5 mg / L and 10 mg / L.

[0023] The invention utilizes ferric hydroxide to adsorb trace tin in brine to obtain a precipitate, then uses a 0.18 mol / L sulfuric acid solution to treat the precipitate to completely dissolve the precipitate, and utilizes inductively coupled plasma spectroscopy to measure its strength, which is proportional to the concentration of tin.

[0024] The present invention discloses the following technical effects:

[0025] The present invention utilizes ferric hydroxide coprecipitation to separate trace tin in brine, and then utilizes inductively coupled plasma spectrometry to determine the tin content. The method eliminates the influence of matrix salt (because the salt content in the brine is too high and the tin content is low, direct measurement cannot obtain the measurement result of the tin content), has a low detection limit, high sensitivity, simple and fast operation, and a detection limit of (3s / N)=0.37μg / mL. The spiked recovery rate is 98.6%-102%. Using 0mg·L -1 The standard series points were measured 11 times continuously, and the relative standard deviation (n=11) was 2.14%. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0032] The brine used in the specific embodiment of the present invention is chloride brine, which is the brine of the Chaerhan Salt Lake in Qinghai Province.

[0033] The standard stock solutions of tin with concentrations of 1 mg / mL, 10 μg / mL, and 1 μg / mL were diluted to 1000 mL with 0.18 mol / L sulfuric acid (prepared before use) to obtain standard solutions, wherein the tin ion concentrations of the standard solutions were 0 mg / L, 0.25 mg / L, 0.5 mg / L, 1 mg / L, 3 mg / L, 5 mg / L, and 10 mg / L, respectively. The standard solutions were measured using inductively coupled plasma spectrometry, and it was found that tin was linearly related in the range of 0-10 mg / L, and the linear regression equation was: intensity = 128.90028930*concentration+5.74943123, and the correlation coefficient was 0.99996.

[0034] Use 0mg·L -1 The standard series points were measured 11 times in succession. The results are shown in Table 1. The relative standard deviation (n=11) was 2.14%.

[0035] Table 1

[0036]

[0037] The determinations of the following examples were performed based on the above linear regression equation.

[0038] Example 1

[0039] The method for determining trace tin in brine (chloride type brine) comprises the following steps:

[0040] S1. Add the same volume of water to 250 mL of brine, then adjust the pH value to 9 using 0.5 mol / L sodium hydroxide solution, then add 20 mg of ferric chloride in the form of an aqueous solution with a concentration of 10 mg / mL, stir the reaction at a speed of 100 rpm for 30 minutes, and then separate the solid and liquid to obtain a precipitated product;

[0041] S2. Add 0.18 mol / L sulfuric acid solution to the precipitated product until the precipitate is completely dissolved to obtain a test solution;

[0042] S3. The tin content in the test solution was determined to be 0.028 μg / L using inductively coupled plasma spectrometry. 2.0 μg of tin was added and 1.972 μg was measured.

[0043] Directly using inductively coupled plasma spectrometry to determine the brine in step S1, the tin content value obtained is too salty and causes serious interference, so no measurement value can be obtained. This shows that eliminating the interference of matrix salt is crucial for determining trace tin in brine.

[0044] Example 2

[0045] Compared with Example 1, the only difference is that the stirring reaction time in step S1 is 5 min, 10 min, 15 min, 20 min, 25 min, 35 min, 40 min, 45 min or 50 min.

[0046] Test Example 1

[0047] The method of Example 1 and Example 2 was used to detect the tin content in the chloride brine. The results are shown in Table 2.

[0048] During the detection, the recovery rate of tin was determined by adding a spike. In step S1 of Example 1 and Example 2, 20 μg of tin was added to 250 mL of brine after adding the same volume of water, and then the pH value was adjusted. The other steps were the same as in Example 1 and Example 2. The results are shown in Table 2.

[0049] Table 2 Effect of stirring time on enrichment efficiency

[0050]

[0051]

[0052] It can be seen from the data in Table 2 that the optimal enrichment efficiency is achieved when the stirring reaction (enrichment) time is 30 minutes or more.

[0053] Example 3

[0054] Compared with Example 1, the only difference is that the pH is adjusted to 7, 8, 10 or 11 in step S1.

[0055] Test Example 2

[0056] The method of Experimental Example 1 was used to detect the tin content in the chloride-type brine. The results are shown in Table 3.

[0057] Table 3 Effect of pH on trace tin enrichment

[0058] pH 7 8 9 10 11 Sn content / μg 1.012 1.972 1.984 1.980 0.974

[0059] It can be seen from the data in Table 3 that when the pH value of the solution is adjusted to 8-10, Fe(OH) 3 The precipitation is complete; when pH is less than 8, Fe(OH) 3 Incomplete generation affects the enrichment efficiency; when pH>10, due to the large amount of Mg contained in the brine 2+ A large amount of Mg(OH) will be generated 2 The influence of Fe(OH) 3 For the enrichment of trace tin, the pH value should be controlled at 8-10 to achieve the best enrichment effect.

[0060] Example 4

[0061] Compared with Example 1, the difference is that the brine selected is sulfate brine.

[0062] Test Example 3

[0063] The same method as in Experimental Example 1 was used for detection, and the content and spiked recovery are shown in Table 4.

[0064] Table 4

[0065]

[0066] It can be seen from the data in Table 4 that the method of the present invention is applicable to the detection of trace tin in different brines.

[0067] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining trace tin in brine, characterized in that the steps include: The pH value of the brine is adjusted to 8-10, and then ferric chloride is added, and after stirring for reaction, the solid product is collected; Add sulfuric acid solution dropwise to the solid product until it is completely dissolved to obtain a solution to be tested; The tin content in the solution to be tested is determined by inductively coupled plasma spectroscopy.

2. The method according to claim 1, characterized in that The brine is chloride brine or sulfate brine.

3. The method according to claim 1, characterized in that The pH value is adjusted to 8-10 by using sodium hydroxide solution.

4. The method according to claim 1, characterized in that The dosage ratio of the ferric chloride to the brine is 20 mg:250 mL.

5. The method according to claim 4, characterized in that The ferric chloride was added in the form of an aqueous solution with a concentration of 10 mg / mL.

6. The method according to claim 1, characterized in that The stirring reaction is carried out at a speed of 80-120 rpm and the reaction time is not less than 30 min.

7. The method according to claim 1, characterized in that The concentration of the sulfuric acid solution is 0.18 mol / L.

8. The method according to claim 1, characterized in that The step of determining the tin content in the solution to be tested by inductively coupled plasma spectroscopy comprises: By measuring the standard solution of tin, the linear relationship of tin in the range of 0-10 mg / L was obtained; Then, the solution to be tested is measured, and the tin content in the solution to be tested is obtained based on the linear relationship of tin in the range of 0-10 mg / L.

9. The method according to claim 8, characterized in that The concentration of iron ions in the standard tin solution is 80 mg / 100 mL.

10. The method according to claim 8, characterized in that The concentrations of tin in the standard tin solution are 0 mg / L, 0.25 mg / L, 0.5 mg / L, 1 mg / L, 3 mg / L, 5 mg / L and 10 mg / L.

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