Rapid detection method and kit for anionic synthetic detergent in tableware

Abstract

The invention relates to a rapid detection method and kit for an anionic synthetic detergent in tableware, and the detection method comprises the following steps: washing the tableware with pure water, and collecting a washing solution; taking the washing liquid, sequentially adding a methyl violet solution and ethyl acetate into the washing liquid, uniformly shaking, and standing for a period of time; and sucking supernatant liquid, comparing the supernatant liquid with a standard colorimetric card in color, and calculating the concentration of the anionic synthetic detergent in the washing liquid according to the color gradation of the standard colorimetric card. The detection method provided by the invention has the advantages of simple pretreatment operation and convenient detection, and is suitable for rapid detection requirements; and 2) the lowest detection mass concentration of the detection method provided by the invention is 0.04 mg / L, which is lower than 0.05 mg / L required by the limit of GB 14934-2016, and the detection method has higher sensitivity and can completely meet the requirement of limit supervision on the anion synthetic detergent.

Description

Technical Field

[0001] The invention relates to the field of chemical detection, and in particular to a method and a kit for rapid detection of anionic synthetic detergents in tableware. Background Art

[0002] Anionic synthetic detergents are the main active ingredients of washing powder, laundry detergent, and dishwashing liquid. The use of such products in daily life will produce anionic surfactant wastewater. Anionic surfactants have the advantages of being easy to use, easy to dissolve, stable, and low cost. They are widely used in the cleaning of tableware in hotels, restaurants, canteens, etc. Anionic synthetic detergents are toxic to a certain extent. If the tableware is not fully rinsed during cleaning, detergents will remain on the tableware and accumulate in the human body through food, endangering human health. It may also cause acute poisoning in people, and the main manifestations of poisoning are symptoms of the central nervous system and gastrointestinal tract. Therefore, my country has formulated GB 14934-2016 "National Food Safety Standard for Disinfection of Tableware (Drinking)", which stipulates that the residual amount of anionic synthetic detergents in tableware (drinking) disinfected by chemical disinfection should not be detected. The regulatory departments at all levels of the state, provinces, and cities have included the residual anionic synthetic detergents in tableware in the sampling monitoring items.

[0003] At present, the main methods for detecting anionic synthetic detergents are spectrophotometry and flow injection method. Spectrophotometry methods include: methylene blue spectrophotometry, phenanthroline extraction spectrophotometry, and the principle of spectrophotometry is to use positively charged ion complexes to react with negatively charged anionic synthetic detergents to form complexes that are insoluble in water but soluble in organic solvents, and then extract with chloroform to quantitatively determine the content of anionic synthetic detergents in the sample by measuring the absorbance value according to the depth of color in the organic layer. Flow injection method uses a continuous flow instrument for continuous online detection, which saves manpower and improves efficiency. All of the above methods can accurately quantify, but the required instruments are expensive, time-consuming, and the detection steps are complicated, which is not conducive to rapid on-site detection. Summary of the invention

[0004] In view of the problems of complicated detection steps and inability to separate the organic layer in the current standard test methods, this paper provides a simple-to-operate and highly sensitive rapid detection method and kit for anionic synthetic detergents in tableware, which can provide certain technical support for the supervision of anionic synthetic detergents in tableware.

[0005] The specific technical solutions are as follows:

[0006] The first aspect of the present invention is to provide a method for rapid detection of anionic synthetic detergents in tableware, comprising:

[0007] Wash tableware with pure water and collect the washing liquid;

[0008] Take the washing liquid, add methyl violet solution and ethyl acetate to it in sequence, shake well and let it stand for a while;

[0009] Aspirate the upper clear liquid and compare its color with the standard colorimetric card. Calculate the concentration of anionic synthetic detergent in the washing liquid based on the color depth of the standard colorimetric card.

[0010] Furthermore, when washing, the surface area of ​​tableware in contact with food is calculated as per 1cm 2 The contact area was washed with 1 mL of pure water.

[0011] Furthermore, the volume of the washing solution is not less than 20 mL, the volume of the methyl violet solution is 1.5-2.5 mL, and the volume of ethyl acetate is 4-6 mL.

[0012] Furthermore, the concentration of the methyl violet solution is 18-22 mg / L.

[0013] Further, the preparation method of the standard colorimetric card is:

[0014] Prepare a standard solution of sodium dodecylbenzene sulfonate with gradient concentrations;

[0015] Add methyl violet solution and ethyl acetate to the sodium dodecylbenzene sulfonate standard solution in sequence, shake well and let stand for a while;

[0016] Aspirate the upper clear liquid to obtain standard color scale solutions, and print standard color comparison cards according to the color values ​​of each standard color scale solution.

[0017] Furthermore, the concentrations of the sodium dodecylbenzenesulfonate standard solution are 0.00 mg / L, 0.040 mg / L, 0.050 mg / L, 0.10 mg / L, 0.20 mg / L, 0.40 mg / L, 0.50 mg / L, 1.0 mg / L, and 2.0 mg / L, respectively.

[0018] Furthermore, the volume of the sodium dodecylbenzenesulfonate standard solution is not less than 20 mL, the volume of the methyl violet solution is 1.5-2.5 mL, and the volume of ethyl acetate is 4-6 mL.

[0019] Furthermore, the concentration of the methyl violet solution is 20 mg / L.

[0020] The second aspect of the present invention is to provide a rapid detection kit for anionic synthetic detergents in tableware, comprising a washing liquid, an extracting liquid, and a color developing liquid; wherein the washing liquid is pure water, the extracting liquid is ethyl acetate, and the color developing liquid is a methyl violet solution.

[0021] Furthermore, the kit also includes an area measuring device, which is a ruler-type tool, including but not limited to a folding ruler, a ruler or a vernier caliper and other conventional tools that can calculate or read the area.

[0022] In the present invention, sodium dodecylbenzene sulfonate (SDBS), a main component of anionic synthetic detergent, reacts with a color developer such as methyl violet to form a purple organic dye with obvious color and high recognizability, and then the purple organic dye is extracted with an organic solvent to form a system with different color depths, which is then compared with a standard colorimetric card to determine the residual amount of anionic synthetic detergent in tableware.

[0023] Considering that ethyl acetate has a lower density than water, is slightly soluble in water, and has low toxicity, it can easily meet market regulatory requirements. Therefore, ethyl acetate is selected as the extraction solvent in the present invention. The selection and use of the above extraction solvent allows the upper clear liquid to be quickly separated using only a rubber-tipped dropper, thereby further meeting the needs of rapid detection.

[0024] The beneficial effects of the above scheme are:

[0025] 1) The detection method provided by the present invention has simple pre-treatment operation and convenient detection, and is suitable for rapid detection needs;

[0026] 2) The minimum detection mass concentration of the detection method provided by the present invention is 0.04 mg / L, which is lower than the limit requirement of 0.05 mg / L in GB 14934-2016. It has higher sensitivity and can fully meet the requirements for the limit regulation of anionic synthetic detergents. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the color diagram of the standard color scale solution of sodium dodecylbenzenesulfonate;

[0028] Figure 2 The diagram is a color diagram of each sodium dodecylbenzene sulfonate standard solution when the rapid detection method provided by the present invention is used for detection. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0032] An embodiment of the present invention provides a method for rapid detection of anionic synthetic detergents in tableware, comprising:

[0033] Use a vernier caliper to calculate the surface area of ​​tableware in contact with food, and then take samples according to the sampling method specified in GB 14934-2016 National Food Safety Standard for Disinfected Tableware (Drinking Utensils), that is, take samples every 100cm 2 Wash the tableware with pure water at a ratio of 100 mL of pure water to the contact surface area, and collect the washing liquid; use a measuring cylinder to measure 20 mL of washing liquid, add 2 mL and 20 mg / L methyl violet solution and 5 mL of ethyl acetate (analytical grade) thereto in sequence, shake well and let stand for 1 min; use a rubber-tipped dropper to draw the upper clear liquid into a 5 mL centrifuge tube, compare the color with the standard colorimetric card, and calculate the concentration of anionic synthetic detergent in the washing liquid according to the color depth of the standard colorimetric card.

[0034] The preparation method of the standard colorimetric card of the present invention is as follows: prepare a sodium dodecylbenzene sulfonate standard solution with gradient concentrations of 0.00 mg / L, 0.040 mg / L, 0.050 mg / L, 0.10 mg / L, 0.20 mg / L, 0.40 mg / L, 0.50 mg / L, 1.0 mg / L and 2.0 mg / L respectively; use a measuring cylinder to measure 20 mL of the sodium dodecylbenzene sulfonate standard solution, add 2 mL and 20 mg / L of methyl violet solution and 5 mL of ethyl acetate (analytical grade) respectively thereto, shake well and let stand for 1 minute; use a rubber dropper to absorb the upper clear liquid to obtain a standard color scale solution (such as Figure 1 As shown), a standard colorimetric card is printed according to the color value of each standard color scale solution.

[0035] In the present invention, sodium dodecylbenzene sulfonate standard solution is prepared with pure water to form sodium dodecylbenzene sulfonate standard solution with concentrations of 0 mg / L, 0.01 mg / L, 0.02 mg / L, 0.03 mg / L, 0.04 mg / L and 0.05 mg / L, and the test is performed as described above, with the blank sample as the reference, to observe whether the color of each sample can be recognized by the naked eye. Figure 2 As shown, the blank sample is colorless and transparent, and the samples at a concentration of 0.040 mg / L and above have a distinct purple color. By conversion, the detection limit of the method provided by the present invention is 0.004 mg / 100 cm 2 .

[0036] In order to verify whether the rapid detection method provided by the present invention is consistent with the results measured by the national standards, industry standards or verified normative methods involved in the corresponding projects (GB 14934-2016 "National Food Safety Standard for Disinfection of Tableware (Drinking Utensils") stipulates that anionic synthetic detergents (calculated as sodium dodecylbenzene sulfonate) in tableware shall not be detected), 50 sample liquids are selected for random inspection in the present invention, and the test is carried out according to the method provided by the present invention, among which 6 samples with obvious purple color are screened out, and 44 samples are colorless samples; GB / T 5750.4-2006 "Standard Test Method for Drinking Water Sensory Properties and Physical Indicators" (methylene blue spectrophotometry) is used as a reference method, and the 6 samples are tested again to confirm that they are indeed unqualified samples and 44 samples are qualified samples. This shows that the rapid detection method provided by the present invention is consistent with the results of the reference method, with a specificity of 100%.

[0037] In the present invention, 25 samples of laboratory tested liquid were taken (divided into positive samples and negative samples), and colorimetric analysis was performed according to the rapid detection method provided by the present invention. The sample results were consistent with the results of the reference method GB / T 5750.4-2006 "Standard Test Method for Drinking Water Sensory Properties and Physical Indicators" (Methylene Blue Spectrophotometry). This shows that the false negative rate of the rapid detection method provided by the present invention is 0%, and the false positive rate is 0%.

[0038] It should be noted that the conventional principle of GB 14934-2016 "National Food Safety Standard for Disinfecting Tableware (Drinking Utensils)" and similar spectrophotometric methods is: using positively charged ion complexes to react with negatively charged anionic synthetic detergents to form complexes that are insoluble in water and soluble in organic solvents, extracting with chloroform or other organic solvents, and then measuring the absorbance value of the color developing solution to quantitatively determine the content of anionic synthetic detergents in the sample. The above-mentioned spectrophotometric detection steps are cumbersome and time-consuming, and require the use of a matching instrument spectrophotometer, which cannot meet the needs of rapid detection. In the present invention, after preparing the standard colorimetric card, only methyl violet and ethyl acetate need to be added and left to stand for a while to perform rapid detection, and the results are correct, the overall operation takes a short time, and can meet the needs of rapid detection.

[0039] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A rapid detection method for anionic synthetic detergents in tableware, characterized in that: include: Wash tableware with pure water and collect the washing liquid; Take the washing liquid, add methyl violet solution and ethyl acetate to it in sequence, shake well and let it stand for a while; Aspirate the upper clear liquid and compare its color with the standard colorimetric card. Calculate the concentration of anionic synthetic detergent in the washing liquid based on the color depth of the standard colorimetric card.

2. The method for rapid detection of anionic synthetic detergents in tableware according to claim 1, characterized in that: When washing, the surface area of ​​tableware in contact with food is measured at 1 cm 2 The contact area was washed with 1 mL of pure water.

3. The method for rapid detection of anionic synthetic detergents in tableware according to claim 1, characterized in that: The volume of the washing solution is not less than 20 mL, the volume of the methyl violet solution is 1.5-2.5 mL, and the volume of ethyl acetate is 4-6 mL.

4. The method for rapid detection of anionic synthetic detergents in tableware according to claim 3, characterized in that: The concentration of methyl violet solution is 18-22 mg / L.

5. The method for rapid detection of anionic synthetic detergents in tableware according to claim 1, characterized in that: The preparation method of the standard colorimetric card is: Prepare a standard solution of sodium dodecylbenzene sulfonate with gradient concentrations; Add methyl violet solution and ethyl acetate to the sodium dodecylbenzene sulfonate standard solution in sequence, shake well and let stand for a while; Aspirate the upper clear liquid to obtain standard color scale solutions, and print standard color comparison cards according to the color values ​​of each standard color scale solution.

6. The method for rapid detection of anionic synthetic detergents in tableware according to claim 5, characterized in that: The concentrations of sodium dodecylbenzenesulfonate standard solution are 0.00 mg / L, 0.040 mg / L, 0.050 mg / L, 0.10 mg / L, 0.20 mg / L, 0.40 mg / L, 0.50 mg / L, 1.0 mg / L, and 2.0 mg / L, respectively.

7. The method for rapid detection of anionic synthetic detergents in tableware according to claim 5, characterized in that: The volume of the sodium dodecylbenzenesulfonate standard solution is not less than 20 mL, the volume of the methyl violet solution is 1.5-2.5 mL, and the volume of ethyl acetate is 4-6 mL.

8. The method for rapid detection of anionic synthetic detergents in tableware according to claim 5, characterized in that: The concentration of methyl violet solution is 20 mg / L.

9. A rapid detection kit for anionic synthetic detergents in tableware, characterized in that: It includes washing liquid, extracting liquid and developing liquid; wherein the washing liquid is pure water, the extracting liquid is ethyl acetate and the developing liquid is methyl violet solution.

10. The rapid detection kit for anionic synthetic detergents in tableware according to claim 9, characterized in that: The kit also includes an area measurer, which is a ruler-type tool.

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