Rapid detection method for active oxygen content in washing salt

Abstract

The invention discloses a method for rapidly detecting the content of active oxygen in washing salt, and belongs to the technical field of analytical chemistry. According to the detection method provided by the invention, the defoaming dispersant is added, so that physical defoaming can be realized, the polarity of the solution can be reduced, the wrapping effect of surfactant micelles in the sample to be detected on iodine molecules or triiodide ions is reduced, and the color mutation at the titration end point is acute; meanwhile, the metal ion masking agent is complexed with interference metal ions, so that the catalyst is ensured to catalyze the oxidation-reduction reaction of peroxide and iodide ions, and the balance of'fast 'and'standard' is realized; in addition, the detection method disclosed by the invention is remarkably shortened in time, and has the advantages of good detection accuracy and high efficiency; moreover, the detection method is not only suitable for a pure sodium percarbonate raw material, but also suitable for a finished product washing salt containing a high-concentration surfactant and an enzyme preparation; therefore, the method is suitable for industrial large-scale detection application.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry technology, specifically relating to a rapid method for detecting the content of reactive oxygen species in washing salt. Background Technology

[0002] Washing salts (such as fruit and vegetable washing salt, dishwasher salt, and active oxygen laundry granules) typically contain peroxides such as sodium percarbonate and sodium perborate as their main active ingredients. The "active oxygen" they release has extremely strong bactericidal, bleaching, and stain-removing abilities. Therefore, the active oxygen content is a core indicator for measuring the quality of washing salts and their stain-removing effect.

[0003] Currently, the conventional methods for detecting reactive oxygen species in peroxides mainly refer to the redox titration methods (primarily the potassium permanganate method and iodometric method) in national standards (such as GB / T 19106-2003 sodium hypochlorite solution or HG / T 2764-2008 sodium percarbonate). However, when testing a specific finished product like washing salt, existing technologies have the following problems: 1) Severe matrix interference: Washing salt formulations are complex, usually containing large amounts of surfactants (foaming agents), fragrances, enzymes, and chelating agents. When using the traditional iodometric method, the foam generated by the surfactants adsorbs iodine molecules, resulting in a less sensitive color change at the titration endpoint, or even a "color reversal" phenomenon, which seriously affects the accuracy of the reading; 2) Slow reaction rate: Some encapsulated or slow-release washing salt particles dissolve and release reactive oxygen species slowly in cold water, resulting in long detection times and a tendency for low detection results due to volatilization; 3) Metal ion interference: Trace amounts of metal ions (such as iron and copper) mixed in washing salt can catalyze the ineffective decomposition of hydrogen peroxide, leading to unstable detection results.

[0004] Therefore, there is an urgent need for a method for detecting reactive oxygen species in washing salts that can eliminate surfactant interference, react rapidly, and produce accurate results, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid method for detecting the active oxygen content in washing salt. This method addresses the problems of severe matrix interference, metal ion interference, poor detection accuracy, and low efficiency in existing washing salt detection processes.

[0006] In a first aspect, the present invention provides a rapid detection method for the content of reactive oxygen species in washing salt, comprising the following steps: S1, adding water, defoaming dispersant, and metal ion masking agent to the sample to be tested to obtain a first mixture; S2, adding potassium iodide and sulfuric acid solution to the first mixture, then adding a catalyst and sealing with water, and reacting in the dark; after the reaction is completed, titrating with standard sodium thiosulfate solution, when the solution changes from dark brown to light yellow, adding starch indicator solution, and continuing titration until the blue color just disappears, which is the endpoint, and recording the volume of standard sodium thiosulfate solution consumed by the sample to be tested; S3, performing a blank experiment according to steps S1 and S2, and recording the volume of standard sodium thiosulfate solution consumed by the blank sample; S4, calculating the content of reactive oxygen species in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0007] In this invention, the inventors discovered that by adding an antifoaming dispersant, not only can physical defoaming be achieved, but the polarity of the solution can also be reduced, thereby decreasing the encapsulation effect of surfactant micelles on iodine molecules or triiodine ions in the sample and making the color change at the titration endpoint more acute. Simultaneously, the metal ion masking agent complexes and interferes with metal ions, ensuring the catalyst catalyzes the redox reaction between peroxides and iodine ions, achieving a balance between speed and accuracy. Furthermore, the detection method of this invention significantly reduces the detection time and has the advantages of high accuracy and efficiency; therefore, it is suitable for large-scale industrial detection applications.

[0008] In some implementations, in step S1, the mass-to-volume ratio of the sample to be tested, water, defoaming dispersant, and metal ion masking agent is (1.0000-1.5000g):(60-100mL):(3-8mL):(2-5mL).

[0009] In some embodiments, in step S1, the defoaming dispersant includes at least one of a mixture of ethanol and n-octanol, or a polyether defoamer.

[0010] In some implementations, the volume ratio of ethanol to n-octanol in the mixture of ethanol and n-octanol is (8-12):1.

[0011] In some embodiments, in step S1, the metal ion masking agent comprises a disodium ethylenediaminetetraacetate solution, and the concentration of the metal ion masking agent is 0.05-0.1 mol / L.

[0012] In some implementations, in step S2, the mass-to-volume ratio of the sample to be tested to the sulfuric acid solution is (1.0000-1.5000 g): (30-45 mL).

[0013] In some implementations, the concentration of the sulfuric acid solution in step S2 is 8-12%.

[0014] In some embodiments, in step S2, the catalyst comprises an ammonium molybdate solution, the concentration of the catalyst is 2-4%, and the amount of catalyst added is 2-4 drops.

[0015] In some implementations, the reaction time in the dark in step S2 is 2-5 minutes.

[0016] In some implementations, in step S2, the concentration of the standard sodium thiosulfate solution is 0.05-0.15 mol / L; the mass-to-volume ratio of the sample to be tested to the starch indicator solution is (1.0000-1.5000 g): (6-9 mL), and the concentration of the starch indicator solution is 3-7 g / L.

[0017] The beneficial effects of this invention are as follows: Unlike existing technologies, the detection method provided by this invention, by adding an antifoaming and dispersing agent, not only can physical defoaming be achieved, but the polarity of the solution can also be reduced, thereby reducing the encapsulation effect of surfactant micelles on iodine molecules or triiodine ions in the sample to be tested, making the color change at the titration endpoint more acute; at the same time, the metal ion masking agent complexes and interferes with the metal ions, ensuring that the catalyst catalyzes the redox reaction between peroxides and iodine ions, achieving a balance between speed and accuracy; in addition, the detection method of this invention significantly shortens the detection time and has the advantages of good detection accuracy and high efficiency; therefore, it is suitable for large-scale industrial detection applications. Attached Figure Description

[0018] Figure 1 This is a flowchart of the rapid detection method for active oxygen content in washing salt according to the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0021] Currently, existing methods for detecting washing salts suffer from problems such as severe matrix interference, metal ion interference, poor detection accuracy, and low efficiency.

[0022] To address the problems of severe matrix interference, metal ion interference, poor detection accuracy, and low efficiency in existing washing salt detection processes, this invention provides a rapid method for detecting the active oxygen content in washing salt.

[0023] In a first aspect, the present invention provides a rapid detection method for the content of reactive oxygen species in washing salt, comprising the following steps: S1, adding water, defoaming dispersant, and metal ion masking agent to the sample to be tested to obtain a first mixture; S2, adding potassium iodide and sulfuric acid solution to the first mixture, then adding a catalyst and sealing with water, and reacting in the dark; after the reaction is completed, titrating with standard sodium thiosulfate solution, when the solution changes from dark brown to light yellow, adding starch indicator solution, and continuing titration until the blue color just disappears, which is the endpoint, and recording the volume of standard sodium thiosulfate solution consumed by the sample to be tested; S3, performing a blank experiment according to steps S1 and S2, and recording the volume of standard sodium thiosulfate solution consumed by the blank sample; S4, calculating the content of reactive oxygen species in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0024] In the detection method provided by this invention, the addition of an antifoaming and dispersing agent not only physically defoams but also reduces the polarity of the solution, thereby reducing the encapsulation effect of surfactant micelles on iodine molecules or triiodine ions in the sample and making the color change at the titration endpoint more acute. Simultaneously, the metal ion masking agent complexes and interferes with metal ions, ensuring the catalyst catalyzes the redox reaction between peroxides and iodine ions, achieving a balance between speed and accuracy. Furthermore, the detection method of this invention significantly reduces the detection time and has the advantages of high accuracy and efficiency. Moreover, the detection method of this invention is not only applicable to pure sodium percarbonate raw materials but also to finished washing salts containing high concentrations of surfactants and enzymes; therefore, it is suitable for large-scale industrial detection applications.

[0025] In some implementations, in step S1, the mass-to-volume ratio of the sample to be tested, water, defoaming dispersant, and metal ion masking agent is (1.0000-1.5000g):(60-100mL):(3-8mL):(2-5mL).

[0026] In this invention, by controlling the mass-volume ratio of the sample to be tested, water, defoaming dispersant, and metal ion masking agent within a specific range, interference can be eliminated, the reaction can be completed, and the accuracy of detection can be significantly improved.

[0027] In some embodiments, in step S1, the defoaming dispersant includes at least one of a mixture of ethanol and n-octanol, and a polyether defoamer, preferably a mixture of ethanol and n-octanol.

[0028] In this invention, by selecting a specific defoaming and dispersing agent, not only can defoaming be achieved, but the color change at the titration endpoint can also be made more acute, thereby further improving the accuracy of detection.

[0029] In some implementations, the volume ratio of ethanol to n-octanol in the mixture of ethanol and n-octanol is (8-12):1.

[0030] It is understood that the volume ratio of ethanol to n-octanol can be routinely adjusted according to actual usage needs, as long as the color change at the titration endpoint is sharp. For example, in this invention, the preferred volume ratio of ethanol to n-octanol is (8-12):1, more preferably 10:1.

[0031] In some embodiments, in step S1, the metal ion masking agent comprises a disodium ethylenediaminetetraacetate solution, and the concentration of the metal ion masking agent is 0.05-0.1 mol / L.

[0032] In this invention, by controlling the concentration of the metal ion masking agent within a specific range, matrix interference can be completely eliminated, thereby significantly improving the accuracy of detection.

[0033] In some implementations, in step S2, the mass-to-volume ratio of the sample to be tested to the sulfuric acid solution is (1.0000-1.5000 g): (30-45 mL).

[0034] In some implementations, the concentration of the sulfuric acid solution in step S2 is 8-12%.

[0035] It is understood that the volume and concentration of the added sulfuric acid solution can be routinely adjusted according to actual usage needs, as long as an acidification reaction system can be provided. For example, in this invention, the preferred mass-to-volume ratio of the sample to the sulfuric acid solution is (1.0000-1.5000 g): (30-45 mL); the preferred concentration of the sulfuric acid solution is 8-12%.

[0036] In some embodiments, in step S2, the catalyst comprises an ammonium molybdate solution, the concentration of the catalyst is 2-4%, and the amount of catalyst added is 2-4 drops.

[0037] In this invention, by adding a catalyst, the activation energy of the reaction between hydrogen peroxide and iodide ions can be significantly reduced, shortening the reaction time from the conventional 30 min to 2-5 min.

[0038] In some implementations, the reaction time in the dark in step S2 is 2-5 minutes.

[0039] In some implementations, in step S2, the concentration of the standard sodium thiosulfate solution is 0.05-0.15 mol / L; the mass-to-volume ratio of the sample to be tested to the starch indicator solution is (1.0000-1.5000 g): (6-9 mL), and the concentration of the starch indicator solution is 3-7 g / L.

[0040] In this invention, by controlling the concentration of the standard sodium thiosulfate solution, the concentration of the starch indicator solution, and the amount added within a specific range, the titration reaction can be completed, thereby significantly improving the accuracy of detection.

[0041] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] Please see Figure 1 This is a flowchart of a rapid detection method for the content of active oxygen in washing salt according to the present invention. Specifically, the rapid detection method includes the following steps: S1, adding water, defoaming dispersant, and metal ion masking agent to the sample to be tested to obtain a first mixture; S2, adding potassium iodide and sulfuric acid solution to the first mixture, then adding a catalyst and sealing with water, and placing it in the dark for reaction; after the reaction is completed, titrating with standard sodium thiosulfate solution, when the solution changes from dark brown to light yellow, adding starch indicator solution, and continuing titration until the blue color just disappears, which is the endpoint, and recording the volume of standard sodium thiosulfate solution consumed by the sample to be tested; S3, performing a blank experiment according to steps S1 and S2, and recording the volume of standard sodium thiosulfate solution consumed by the blank sample; S4, calculating the content of active oxygen in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0043] Example 1 In this embodiment, the active oxygen content in a certain brand of fruit and vegetable washing salt (regular type) is rapidly detected, including the following steps: S1. Accurately weigh 1.5000g of fruit and vegetable washing salt and place it in an iodine flask; then add 100mL of water, 5mL of a mixture of ethanol and n-octanol (volume ratio of 10:1), and 2mL of 0.05mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution to obtain the first mixture. S2. Add excess potassium iodide and 45 mL of 10% sulfuric acid solution to the first mixture, then add 3 drops of 3% ammonium molybdate solution and seal with water, and place in the dark to react for 5 min. After the reaction is complete, titrate with 0.1 mol / L standard sodium thiosulfate solution. When the solution changes from dark brown to light yellow, add 9 mL of starch indicator solution (5 g / L) and continue titrating until the blue color just disappears, which is the endpoint. Record the volume of standard sodium thiosulfate solution consumed by the sample. S3. Perform a blank experiment according to steps S1 and S2, and record the volume of standard sodium thiosulfate solution consumed by the blank sample. S4. Calculate the content of active oxygen in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0044] Among them, the active oxygen content in the washing salt ( X The formula for calculating (in terms of mass fraction) is as follows:

[0045] In the formula, V : The volume (mL) of standard sodium thiosulfate solution consumed by the sample to be tested. V 0: Volume (mL) of standard sodium thiosulfate solution consumed by the blank sample; c : Concentration of standard sodium thiosulfate solution (mol / L); 0.008: Mass of active oxygen in grams equivalent to 1.00 mL of standard sodium thiosulfate solution, Na2S2O3 = 1.000 mol / L; m Mass of the sample to be tested (g).

[0046] After five parallel repetitions of the experiment, the calculated reactive oxygen species content in the fruit and vegetable washing salt samples is as follows: X1=11.94%, X2=11.96%, X3=11.95%, X4=11.92%, X5=11.94%.

[0047] Furthermore, the reliability of the test results is verified using a relative standard deviation (RSD) determination algorithm.

[0048] For example, if the same sample is subjected to n parallel measurements (n≥5), the relative standard deviation (RSD) is calculated:

[0049] If RSD ≤ 0.5%, the test result is considered valid; otherwise, the test needs to be repeated.

[0050] Calculations showed that after five repeated experiments, the RSD in this embodiment was 0.19%, indicating that the detection result was valid. The results demonstrate that this method exhibits extremely high precision after eliminating foam interference.

[0051] Example 2 In this embodiment, the active oxygen content in a certain brand of active oxygen laundry granules is rapidly detected, including the following steps: S1. Accurately weigh 1.0000g of laundry detergent granules and place them in an iodine flask; then add 60mL of water, 5mL of a mixture of ethanol and n-octanol (volume ratio of 10:1), and 2mL of 0.05mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution to obtain the first mixture. S2. Add excess potassium iodide and 30 mL of 10% sulfuric acid solution to the first mixture, then add 3 drops of 3% ammonium molybdate solution and seal with water. Let it react in the dark for 3 min. After the reaction is complete, titrate with 0.1 mol / L standard sodium thiosulfate solution. When the solution changes from dark brown to light yellow, add 6 mL of starch indicator solution (5 g / L) and continue titrating until the blue color just disappears. This is the endpoint. Record the volume of standard sodium thiosulfate solution consumed by the sample. S3. Perform a blank experiment according to steps S1 and S2, and record the volume of standard sodium thiosulfate solution consumed by the blank sample. S4. Calculate the content of active oxygen in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0052] The calculated active oxygen content in the laundry granules is as follows: X = 13.16%.

[0053] Further, the recovery rate was verified by spiked analysis. Specifically, a standard hydrogen peroxide solution containing 0.0500g of active oxygen was precisely added to another 1.0000g sample from the same batch. The spiked sample was then analyzed (the defoamer was increased to 8mL), and the total amount of active oxygen in the spiked sample was found to be 0.1812g.

[0054] The spiked recovery rate (P) was verified using the following formula:

[0055] In the formula, X total The total amount of reactive oxygen species measured after spiking; X sample : Background reactive oxygen species content in the sample; m standard Theoretical mass of the added standard reactive oxygen species; m total : Total mass of reactive oxygen species in the spiked sample.

[0056] If the P-value is within the range of 98.0-102.0%, it proves the effectiveness of the defoaming masking system.

[0057] The calculation yielded P=99.2%, proving that the defoaming masking system of the present invention did not cause any loss of active oxygen and could accurately resist interference, with extremely high detection accuracy.

[0058] Example 3 In this embodiment, the rapid detection of active oxygen content in a certain industrial-grade sodium percarbonate raw material containing impurities includes the following steps: S1. Accurately weigh 1.2000g of sample and place it in an iodine flask; then add 80mL of water, 5mL of a mixture of ethanol and n-octanol (volume ratio of 10:1), and 5mL of 0.1mol / L disodium ethylenediaminetetraacetate (EDTA-2Na) solution to obtain the first mixture; S2. Add excess potassium iodide and 40 mL of 10% sulfuric acid solution to the first mixture, then add 3 drops of 3% ammonium molybdate solution and seal with water. Let it react in the dark for 5 min. After the reaction is complete, titrate with 0.1 mol / L standard sodium thiosulfate solution. When the solution changes from dark brown to light yellow, add 7 mL of starch indicator solution (5 g / L) and continue titrating until the blue color just disappears. This is the endpoint. Record the volume of standard sodium thiosulfate solution consumed by the sample. S3. Perform a blank experiment according to steps S1 and S2, and record the volume of standard sodium thiosulfate solution consumed by the blank sample. S4. Calculate the content of active oxygen in the washing salt based on the amount of standard sodium thiosulfate solution used in steps S2 and S3.

[0059] The results showed that the titration endpoint was stable and no metal ion-catalyzed bubbles were generated; the active oxygen content was measured to be 10.50% and the RSD was 0.28% (n=5), which met the quality control requirements.

[0060] Comparative Example 1 In this comparative example, the national standard method was used to test the fruit and vegetable washing salt in Example 1. The method was basically the same as in Example 1, except that the mixture of ethanol and n-octanol, disodium ethylenediaminetetraacetate (EDTA-2Na) solution and ammonium molybdate solution were not added, and the reaction was carried out in the dark for 30 minutes.

[0061] The results showed that the solution produced abundant foam during dissolution, making the liquid surface difficult to observe, and the foam layer also carried some unreacted sample. During titration, the foam adsorbed iodine and turned dark blue. Although the solution became colorless at the endpoint, it quickly turned blue again after about 15 seconds (severe color reversion), making it difficult to determine the endpoint and prone to over-titration.

[0062] The active oxygen content in the fruit and vegetable washing salt was measured to be 11.20% (low), with an RSD of 2.80% (n=5), which does not meet the quality control requirements.

[0063] Furthermore, the test data from Examples 1-3 and Comparative Example 1 were summarized, and the results are shown in Table 1 below.

[0064] Table 1 Data Test Results

[0065] As can be seen from Table 1, the detection method of the present invention has extremely high precision (RSD<0.2%) and accuracy (recovery rate close to 100%) in complex matrices (containing surfactants and impurity metals), which is far superior to the national standard method.

[0066] In summary, by adding an antifoaming and dispersing agent, this invention not only physically defoams but also reduces the polarity of the solution, thereby decreasing the encapsulation effect of surfactant micelles on iodine molecules or triiodine ions in the sample and making the color change at the titration endpoint more acute. Simultaneously, the metal ion masking agent complexes and interferes with metal ions, ensuring the catalyst catalyzes the redox reaction between peroxides and iodine ions, achieving a balance between speed and accuracy. Furthermore, the detection method of this invention significantly reduces the detection time and has the advantages of high accuracy and efficiency.

[0067] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0068] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for rapid detection of active oxygen content in a washing salt, characterized by, The method comprises the following steps: S1, adding water, defoaming dispersant and metal ion masking agent into a sample to be tested to obtain a first mixture; S2, adding potassium iodide and sulfuric acid solution into the first mixture, then adding a catalyst, performing water sealing and placing in dark place for reaction; after the reaction is completed, using standard sodium thiosulfate solution for titration, when the solution changes from dark brown to light yellow, adding starch indicator solution, continuing titration until blue color just disappears as the end point, recording the volume of standard sodium thiosulfate solution consumed by the sample to be tested; S3, performing blank test according to steps S1 and S2, recording the volume of standard sodium thiosulfate solution consumed by the blank sample; S4, calculating the content of active oxygen in the washing salt according to the amount of standard sodium thiosulfate solution in steps S2 and S3.

2. The rapid detection method according to claim 1, characterized in that, In step S1, the mass-volume ratio of the sample to be tested, the water, the defoaming dispersant, the metal ion masking agent is (1.0000-1.5000g):(60-100mL):(3-8mL):(2-5mL).

3. The rapid detection method according to claim 1, characterized in that, In step S1, the defoaming dispersant comprises at least one of a mixture of ethanol and n-octanol, a polyether defoaming agent.

4. The rapid detection method according to claim 3, characterized in that, In the mixture of ethanol and n-octanol, the volume ratio of the ethanol to the n-octanol is (8-12):

1.

5. The rapid detection method of claim 1, wherein, In step S1, the metal ion masking agent comprises disodium ethylenediaminetetraacetate solution, and the concentration of the metal ion masking agent is 0.05-0.1mol / L.

6. The rapid detection method of claim 1, wherein, In step S2, the mass-volume ratio of the sample to be tested to the sulfuric acid solution is (1.0000-1.5000g):(30-45mL).

7. The rapid detection method of claim 1, wherein, In step S2, the concentration of the sulfuric acid solution is 8-12%.

8. The rapid detection method of claim 1, wherein, In step S2, the catalyst comprises ammonium molybdate solution, the concentration of the catalyst is 2-4%, and the addition amount of the catalyst is 2-4 drops.

9. The rapid detection method of claim 1, wherein, In step S2, the time of the reaction in dark place is 2-5min.

10. The rapid detection method of claim 1, wherein, In step S2, the concentration of the standard sodium thiosulfate solution is 0.05-0.15mol / L. The mass-volume ratio of the sample to be tested to the starch indicator solution is (1.0000-1.5000g):(6-9mL), and the concentration of the starch indicator solution is 3-7g / L.

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