CN100594373C - Method for detecting aqueous solution oxalate - Google Patents

Abstract

The invention provides a method for detecting oxalate in aqueous solution. The method is based on Cu ²⁺ ions, using catechol violet as a chromogenic agent, and directly and quantitatively detects oxalate in aqueous solution in a HEPES buffer solution with a pH of 6.0. Oxalate, the determination process is simple, convenient, and the measurement result is accurate. This method has high sensitivity and is not interfered by other anions in aqueous solution, so it can be applied to the detection of oxalate in clinical, food and environment.

Description

A method for detecting oxalate in aqueous solution

Technical field:

The invention relates to a method for detecting oxalate, in particular to a method for detecting oxalate in an aqueous solution.

Background technique:

Oxalic acid is a highly toxic compound that widely exists in plants, animals, and microorganisms. Its accumulation in the body can cause various pathological conditions, such as urolithiasis, hyperoxaluria, and renal failure. Increased oxalate concentration in urine may be a symptom of diabetes and other diseases, and decreased may be acute and chronic nephritis. Excessive oxalic acid in the daily diet can form insoluble matter with calcium before absorption, hindering the absorption of calcium; after absorption, it can form stones with calcium and other substances. It is reported that 70%-80% of kidney stones are mainly composed of calcium oxalate. Beverages sterilized by ozone will form oxalic acid when the content of vitamin C is high, thereby promoting the regeneration of microorganisms and reducing the bactericidal effect. At the same time, oxalic acid is a toxin secreted by fungi and participates in pathogenicity. It has been found in genera such as Sclerotinia, Aspergillus, Chestnutia, Invertia, Rhizoctonia, Sclerotinia and Crystaliella. reports. Oxalic acid plays an important role in the pathogenic process of the above-mentioned fungal genera. From this point of view, the quantitative detection of oxalic acid in aqueous solution is very important.

Regarding the determination of oxalate in aqueous solution, the methods for detecting oxalate at home and abroad in the past can be summarized as follows:

1, titration, with ceric sulfate as titrant, with iron-o-phenanthroline as indicator (Wu Xiaoling etc., Journal of Xinjiang Medical University, 22 (1999) 148);

2. Colorimetric method, oxidizing or reducing oxalic acid, or directly reacting with a certain chromogenic agent to generate colored substances (Shen You et al., Spectroscopy and Spectral Analysis, 18 (1998) 756-758);

3. Ion chromatography (Del Nozal, M.J, J. Chromatograohy A, 881 (2000) 629-638);

4. Capillary electrophoresis analysis method (Bryant, C.N, Chromatography A, 771(1997) 285-299);

5. High-performance liquid chromatography (Yu Le, Peng Xinxiang, Yang Chong, etc., Analytical Chemistry Research Bulletin, 30(2002) 1119-1122);

6. Enzymatic method (Thakue, M., Goyal, L., and Pundie, C.S, J. Biochem Biophys. Methods, 44 (2000) 77-88).

However, there are some problems with the above methods:

1. The titration method has low sensitivity, and the operation is cumbersome and time-consuming;

2. Other colorimetric methods require pre-precipitation, it is difficult to completely extract oxalate, and the operation is cumbersome and the repeatability is poor;

3. Capillary electrophoresis instruments are not popular yet;

4. High-performance liquid chromatography requires the separation of oxalate, and the interference of inorganic acids is serious during the separation process, and the equipment is expensive, and the requirements for operators are high;

5. The high cost of oxalate oxidase limits the wide application of this method.

Invention content:

The object of the present invention is to provide a method for detecting oxalate in aqueous solution with low cost, simple operation and high sensitivity.

The invention provides a method for detecting oxalate in aqueous solution. The method is based on Cu ²⁺ ions, uses catechol violet as a chromogen, and directly and quantitatively detects oxalic acid in aqueous solution in a HEPES buffer solution with a pH of 6.0 root, its specific detection steps include:

1. Prepare a HEPES buffer solution with a concentration of 10 mM at pH 6.0, and prepare Cu ²⁺ solution and catechol violet solution with a concentration of 2 mM respectively;

2. Add the above 2ml HEPES buffer solution to the UV cuvette, as a blank, use a micro-sampler to absorb 10-100μl of the above-mentioned catechol violet solution and add it to the cuvette, at this time the solution changes from colorless to Turn yellow, detect on a UV-Vis spectrophotometer, there is a maximum absorption at 443nm;

3. In the above-mentioned cuvette, add the Cu ²⁺ solution whose molar number is 2 times that of the catechol violet solution. At this time, the solution turns from yellow to blue, and detects on a UV-visible spectrophotometer, and finds the maximum absorption peak From the above 443nm to 624nm;

4. Take the tested oxalate solution, gradually add it into the cuvette with a micro-injector, and detect it on the UV-Vis spectrophotometer while adding the sample. With the addition of the solution, the maximum absorption peak gradually changes from 624nm to 443nm back, the color of the solution also gradually changed from blue to yellow, and when the absorption peak reached the maximum at 443nm and the color of the solution turned yellow completely, stop adding the solution;

5. Calculate the content of oxalate in the solution according to [Cu ²⁺ ]×2×V _Cu /V _oxalate .

The Cu ²⁺ solution is a water-soluble divalent copper inorganic salt solution such as copper chloride, copper nitrate, copper sulfate, copper acetate, copper perchlorate solution and the like.

The method for detecting oxalate in aqueous solution of the invention can be applied to the detection of oxalate in clinical, food and environment.

The selectivity of the detection method for oxalate is specific compared to other anions, that is, the presence of other anions does not interfere with the determination of oxalate by the method. Proof experiment: In the cuvette described in step 3, add acetate, nitrate, carbonate, phosphate, hydrogen phosphate, fluoride, and chlorine with molar numbers 10 times the amount of oxalate in step 4, respectively or sequentially Ions or bromide ions are detected on the ultraviolet-visible spectrophotometer, and the maximum absorption peak at 624nm does not change, and the color of the system does not change.

The present invention has the following advantages: 1. The cost of the detection system is low; 2. It is detected on a UV-visible spectrophotometer, and the detection process is simple, and the effect can be clearly observed with the naked eye to realize the naked eye monitoring; 3. The method shows oxalate It has good selectivity, that is to say, the presence of other anions does not interfere with the detection results; 4. The detection is quantitative, has a large linear range, and the error is small; 5. The detection environment is carried out in aqueous solution, Therefore, this invention can be applied to the detection of oxalate in environmental water sources or clinical body fluids.

Description of drawings:

Fig. 1 is the ultraviolet-visible absorption figure of embodiment 1

Fig. 2 is the ultraviolet-visible absorption figure of embodiment 2

Fig. 3 is the ultraviolet-visible absorption figure of embodiment 3

Fig. 4 is the ultraviolet-visible absorption figure of embodiment 4

Fig. 5 is the color change figure of embodiment 5 detection process

Implementation method:

Example 1:

Prepare HEPES (10mM) buffer solution with pH 6.0, and prepare 2mM Cu(NO ₃ ) ₂ ·3H ₂ O solution, 2mM catechol violet solution and 2mM sodium oxalate solution; add 2ml of HEPES buffer solution to Put it into an ultraviolet cuvette, as a blank, draw 50 μl of 2mM catechol violet solution with a micro-injector, and add it to this cuvette, at this time, the solution turns from colorless to yellow, and the solution is detected on the UV-visible spectrophotometer. Detect, 443nm has maximum absorption; In above-mentioned cuvette, add 2mM Cu ²⁺ 100μl, at this moment the solution turns from yellow to blue, detect on the ultraviolet-visible spectrophotometer, find that the maximum absorption peak changes from above-mentioned 443nm to 624nm; take the sodium oxalate solution, and test it on the HP8453 UV-Vis spectrophotometer while adding the sample. With the addition of oxalate, the maximum absorption peak gradually changes from 624nm to 443nm, and the color of the solution gradually changes from blue to yellow. , when the absorption peak reaches the maximum at 443nm and the color of the solution turns yellow completely, the amount of oxalate added is 200μl; calculation: 100μl×2× ^10-3 ×2/200μl, the content of oxalic acid in the solution is 2mM. The UV-visible absorption diagram is shown in Figure 1.

Example 2:

A 2mM CuCl ₂ ·3H ₂ O solution was prepared, and the rest was the same as in Example 1. The ultraviolet absorption diagram is shown in FIG. 2 .

Example 3:

A 2mM CuSO ₄ ·5H ₂ O solution was prepared, and the rest was the same as in Example 1. The ultraviolet absorption diagram is shown in FIG. 3 .

Example 4:

In the buffer solution containing 50 μM catechol violet and 100 μM Cu(NO ₃ ) ₂ 3H ₂ O, pH 6.0 HEPES (10 mM), add acetate, nitrate, carbonate and phosphoric acid with a molar number 10 times that of oxalate in sequence root, hydrogen phosphate, fluoride ion, chloride ion and bromide ion, the UV absorption diagram is shown in Figure 4.

Example 5

Gradually add 2 mM oxalate solution (0, 50, 100, 150, 200 μl) to the buffer solution containing 50 μM catechol violet and 100 μM Cu(NO ₃ ) ₂ 3H ₂ O, pH 6.0 HEPES (10 mM) . The color change diagram is shown in Figure 5.

Claims (1)

1, a kind of method that detects aqueous solution medium-height grass acid group is characterized in that, comprises following detection step:

(1), the concentration of preparation pH6.0 is the HEPES buffer solution of 10mM, and compound concentration is the Cu of 2mM respectively ²⁺Solution and pyrocatechol violet solution;

(2) the HEPES buffer solution with above-mentioned 2ml is added in the ultraviolet cuvette, as blank, to draw above-mentioned pyrocatechol violet solution 10-100 μ l with microsyringe and be added in the cuvette, this moment, solution was by colourless flavescence look, detect on the UV, visible light spectrophotometer, 443nm has absorption maximum;

(3), in above-mentioned cuvette, add 2 times of molal quantitys again to the Cu of pyrocatechol violet solution ²⁺Solution, solution is detected on the UV, visible light spectrophotometer by xanthochromia indigo plant at this moment, finds that maximum absorption band becomes 624nm by above-mentioned 443nm;

(4), get tested oxalate solution, be added in the cuvette gradually with microsyringe, application of sample limit, limit is detected on the UV, visible light spectrophotometer, adding along with oxalate, maximum absorption band is become again to 443nm gradually by 624nm again, and the color of solution is also returned yellow by blue stain gradually, when absorption peak reaches maximum at 443nm, during the complete flavescence of the color of solution, stop to add oxalate;

(5), by [Cu ²⁺] * 2 * V _Cu/ V _OxalateCalculate the content of oxalate;

Described Cu ²⁺Solution is the solution of cupric chloride, copper nitrate, copper sulphate, Schweinfurt green or cupric perchlorate.

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