Rapid detection method for mercaptoacetic acid substances in cosmetics

Abstract

The invention relates to a rapid detection method for mercaptoacetic acid substances in cosmetics, and belongs to the technical field of rapid detection. The rapid detection method for the mercaptoacetic acid substances in the cosmetics comprises the following steps: (1) uniformly mixing the cosmetics in an extraction solvent to obtain a sample solution; and (2) adding a citric acid solution into the sample solution, uniformly mixing, adding a ferric chloride hydrochloric acid solution, uniformly mixing, and observing the color to obtain a result, thereby completing the rapid detection. Wherein if the color is red or purplish red, the cosmetic contains mercaptoacetic acid or mercaptoacetate; if the color is green, the cosmetic contains isooctyl thioglycolate or butyl thioglycolate. The rapid detection method is simple and efficient, the detection result of the mercaptoacetic acid substances in the cosmetics can be rapidly obtained, the accuracy is high, the detected concentration meets the limit value requirement of the cosmetics, the stability and the specificity are good, and the application value is very high.

Description

Technical Field

[0001] The invention relates to the technical field of rapid detection, and in particular to a method for rapid detection of thioglycolic acid substances in cosmetics. Background Art

[0002] Thioglycolic acid, also known as thioglycolic acid or thioglycolic acid, has a chemical formula of C2H4O2S. It is a toxic, colorless, transparent liquid, and sulfur-containing organic matter with a strong pungent odor. Thioglycolic acid has a strong reducing effect under alkaline conditions. It can react with cystine in hair, cut the disulfide bond of cystine, and undergo chemical changes to soften the hair, which plays a role in curling and shaping the hair. Thioglycolic acid salts and esters have similar effects and are widely used in perming and depilatory cosmetics. In addition, thioglycolic acid ingredients can also be used in rinse-off hair products. There are also reports of using thioglycolic acid ingredients to exfoliate the skin and apply them in other cosmetics.

[0003] However, the use of thioglycolic acid has certain safety hazards. As a perm ingredient, it can damage the hair while changing its shape. Direct contact with the skin can cause erythema and itching. In severe cases, it can cause acute swelling, exudation, pain, and induce chronic dermatitis. The positive rate in the skin irritation test is as high as 85% or more. The results of animal experiments show that long-term contact with thioglycolic acid can cause immune dysfunction, chronic skin toxicity, reproductive toxicity, and mutagenic effects. If the human body is in long-term contact, it will cause damage to the human skin and various tissues and organs, affect human metabolism, and endanger human health. my country's "Cosmetic Safety Technical Specifications" (2015 edition) has listed thioglycolic acid and its salts and thioglycolic acid esters as restricted components of cosmetics, and stipulates that the content of thioglycolic acid and its salts is ≤8% for general perm products, ≤11% for professional perm products, ≤5% for depilatory products, and ≤2% for other rinse-off hair products; the content of thioglycolic acid esters is ≤8% for general perm products and ≤11% for professional perm products (both calculated as thioglycolic acid).

[0004] Currently, the detection methods for thioglycolic acid substances in cosmetics include ion chromatography, high performance liquid chromatography and chemical titration. These detection methods are relatively cumbersome in experimental operation and take a long time to test, and are not suitable for rapid screening requirements in scenarios such as on-site testing.

[0005] Therefore, developing a method for rapid detection of thioglycolic acid-like substances in cosmetics is of high value in application fields such as cosmetics quality monitoring and on-site detection and screening. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a rapid detection method for thioglycolic acid substances in cosmetics. The rapid detection method provided by the present invention can quickly detect thioglycolic acid substances in cosmetics with different matrices, with high detection accuracy, specificity and good stability.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for rapid detection of thioglycolic acid substances in cosmetics, comprising the following steps:

[0009] (1) mixing the cosmetics in an extraction solvent to obtain a sample solution;

[0010] The extraction solvent is a mixture of a standard buffer solution and anhydrous ethanol, the pH of the standard buffer solution is 9.9-10.1, and the volume ratio of the standard buffer solution to anhydrous ethanol is (8-10):1;

[0011] (2) adding citric acid solution to the sample solution and mixing, then adding ferric chloride hydrochloric acid solution and mixing, observing the color and obtaining the result, thereby completing the rapid detection of thioglycolic acid substances in the cosmetics;

[0012] The mass ratio of citric acid in the citric acid solution to ferric chloride in the ferric chloride hydrochloric acid solution is (0.49-1):(0.24-0.25).

[0013] The invention provides a method capable of quickly detecting thioglycolic acid substances in cosmetics, comprising thioglycolic acid and its salts and esters.

[0014] The principle of the detection method of the present invention is: using a suitable extraction solvent to dissolve the thioglycolic acid components from the cosmetic matrix, the thioglycolic acid can reduce the trivalent iron ions in the ferric chloride hydrochloric acid solution to divalent iron ions, and the divalent iron ions can further react with the thioglycolic acid in the ammonia-alkali solution to generate red coordination ions, and the detection is achieved by observing the color. For thioglycolic acid esters such as isooctyl thioglycolate and butyl thioglycolate, the trivalent iron ions can be reduced to divalent iron ions, and the solution is displayed as green, which also achieves detection, but it cannot further react to generate red coordination ions due to structural reasons.

[0015] The rapid detection method of the present invention first adds citric acid solution before adding ferric chloride hydrochloric acid solution, so that citric acid of a specific ratio can be combined with trivalent iron ions added later to form coordination ions, so as to prevent iron from producing red ferric hydroxide precipitation in an alkaline solution and affecting the detection result. After adding ferric chloride hydrochloric acid solution, the observed color depth is related to the amount of thioglycolic acid substances contained in the sample. The greater the content, the darker the color of the color development can be observed. This feature can be reasonably used within a certain concentration range to achieve semi-quantitative detection.

[0016] The ratio of the specific extraction solvent in the present invention, as well as the ratio of the amount of citric acid and ferric chloride added during the color development process, are crucial to the detection of thioglycolic acid substances in cosmetics. When the ratio of the extraction solvent is not appropriate, color development cannot occur; too much citric acid causes the iron ions to be unable to react with thioglycolic acid substances to develop color, while too little citric acid may interfere; too much ferric chloride causes the thioglycolic acid substances to be unable to further develop color, while too little ferric chloride results in an unclear color development effect.

[0017] The rapid detection method of thioglycolic acid substances in cosmetics provided by the present invention is applicable to cosmetics with different matrices, including water-based preparations, creams, etc., and can cover common types of cosmetics on the market that may add thioglycolic acid substances; and the method has high accuracy, good specificity and stability, fast detection speed, low cost, and can provide effective technical support for on-site detection scenarios such as supervision and inspection, and has strong practicality and high application value.

[0018] Preferably, in step (1), the ratio of the mass of the cosmetic to the volume of the extraction solvent is (0.5-1) g:10 mL.

[0019] Preferably, in step (1), the mixing method is vortexing or shaking.

[0020] As a preferred solution, the vortex conditions are: frequency 50-60 Hz, rotation speed 5300-5500 rpm, time 0.5-1.5 min; the shaking is manual shaking 10-15 times.

[0021] When the rapid detection method of thioglycolic acid substances of the present invention is used for rapid screening in the field, if there is no vortex oscillation instrument, the sample can also be mixed by vigorous manual shaking.

[0022] Preferably, in step (1), components of the standard buffer solution include boric acid, potassium chloride and sodium hydroxide.

[0023] Preferably, in step (1), the volume ratio of the standard buffer solution to anhydrous ethanol is 9:1.

[0024] Preferably, in step (2), the volume ratio of the sample solution, the citric acid solution and the ferric chloride solution is sample solution: citric acid solution: ferric chloride solution = (1-2): (0.03-0.05): (0.03-0.05).

[0025] The present invention requires very little amount of detection reagent, has fast color development reaction, high detection efficiency, low cost, and no technical threshold.

[0026] Further preferably, in step (2), the citric acid solution is obtained by dissolving 0.5-1 g of citric acid monohydrate in 100 mL of water and mixing.

[0027] Further preferably, in step (2), the ferric chloride solution is prepared by dissolving 2.5 g of anhydrous ferric chloride in 10 mL of concentrated hydrochloric acid, adding 36 mL of water, mixing, and then diluting 20 times.

[0028] Preferably, in step (2), the color is red or purple, and the result obtained is that the cosmetic contains thioglycolic acid or thioglycolate; the color is green, and the result obtained is that the cosmetic contains isooctyl thioglycolate or butyl thioglycolate.

[0029] Preferably, in the sample solution, the detection concentration of the thioglycolic acid is 100 μg / mL, and the detection concentrations of isooctyl thioglycolate and butyl thioglycolate are 275 μg / mL.

[0030] Under the above detection concentration, calculated based on the weighing amount of the cosmetics as 1 g and the sampling amount as 1 mL, the detection limit of the detection method of the present invention for thioglycolic acid is 1 mg / g, and the detection limit for isooctyl thioglycolate and butyl thioglycolate is 2.75 mg / g, both of which meet the detection requirements of the limit values ​​in my country's "Technical Specifications for Safety of Cosmetics", and can achieve accurate monitoring of thioglycolic acid substances in different cosmetics.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention realizes effective and rapid detection of thioglycolic acid substances in cosmetics by optimizing the ratio of extraction solvent and developer. The detection accuracy, specificity and stability are high, and the detected concentration meets the detection requirements of the limit value of thioglycolic acid substances in cosmetics.

[0033] 2. The detection method of the present invention is applicable to the detection of thioglycolic acid-like substances in cosmetics with different matrices, including aqueous solutions and creams. It can cover common types of cosmetics on the market that may use thioglycolic acid-like substances, such as perming solutions, depilatory creams, and leave-on skin care products suspected of illegal additions, etc., and has a wide range of applications.

[0034] 3. The detection method of the present invention can detect whether the sample contains thioglycolic acid substances through rapid pretreatment and color development steps, and the extraction solution and related reagents used are common chemical reagents. The detection cost is low, the operation is simple and there is no threshold. There is no need to use expensive analytical instruments. The detection is fast and suitable for on-site operation. It is suitable for the requirements of rapid on-site detection by supervisory departments, testing agencies, and various institutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a color development effect diagram of using the rapid detection method of the present invention to detect thioglycolic acid, isooctyl thioglycolate, and butyl thioglycolate;

[0036] Figure 2 This is a color development diagram of the rapid detection method of the present invention using different extraction solvents;

[0037] Figure 3 The figure is a color development effect diagram of the rapid detection method of the present invention using citric acid solutions of different concentrations;

[0038] Figure 4 The diagram is a color development effect diagram of ferric chloride hydrochloric acid solutions with different concentrations in the rapid detection method of the present invention;

[0039] Figure 5 This is a color development diagram of a liquid-based dosage form cosmetic detected using the rapid detection method of the present invention in Example 1;

[0040] Figure 6 This is a diagram showing the color development effect of a depilatory cream detected using the rapid detection method of the present invention in Example 2. DETAILED DESCRIPTION

[0041] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below in conjunction with specific examples. The test methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0042] Experimental Example 1

[0043] In order to explore the minimum detection concentration of the rapid detection method of thioglycolic acid substances in cosmetics of the present invention, the detection method of the present invention is used to detect cosmetic samples containing different concentrations of thioglycolic acid, isooctyl thioglycolate, and butyl thioglycolate, respectively, comprising the following steps:

[0044] 1. Prepare Reagents

[0045] (1) Extraction solvent: 9 parts by volume of standard buffer solution was mixed with 1 part by volume of anhydrous ethanol. The standard buffer solution (pH=10.00) was a commercially available solution (brand: Supeico, main components: boric acid, potassium chloride, sodium hydroxide).

[0046] (2) Citric acid solution: Accurately weigh 0.5 g of citric acid monohydrate and dissolve it in 100 mL of water. Shake well.

[0047] (3) Ferric chloride hydrochloric acid solution: accurately weigh 2.5 g of anhydrous ferric chloride and dissolve it in 10 mL of concentrated hydrochloric acid. Then add 36 mL of water, stir thoroughly to mix, and then dilute 20 times with water.

[0048] (4) Thioglycolic acid single standard solution:

[0049] Weigh 0.02 g of thioglycolic acid standard into a 10 mL volumetric flask, add extraction solvent to dissolve and dilute to the scale, shake well to obtain a single-standard thioglycolic acid stock solution with a mass concentration of 2000 μg / mL; further dilute with extraction solvent to obtain single-standard thioglycolic acid solutions with mass concentrations of 500 μg / mL, 200 μg / mL, 100 μg / mL, and 50 μg / mL, respectively.

[0050] (5) Single standard solution of isooctyl thioglycolate and single standard solution of butyl thioglycolate:

[0051] Weigh 0.02 g of isooctyl thioglycolate standard and butyl thioglycolate standard into a 10 mL volumetric flask, add anhydrous ethanol to dissolve and dilute to the mark, shake well, and use them as isooctyl thioglycolate single standard stock solution and butyl thioglycolate single standard stock solution with a mass concentration of 2000 μg / mL; further dilute with extraction solvent to obtain isooctyl thioglycolate single standard solution and butyl thioglycolate single standard solution with mass concentrations of 500 μg / mL, 275 μg / mL, 250 μg / mL and 100 μg / mL, respectively.

[0052] (6) One sample each of liquid-based cosmetics and cream-based cosmetics that do not contain thioglycolic acid substances.

[0053] 2. Sample Pretreatment

[0054] Weigh 1 g of a cosmetic sample that does not contain thioglycolic acid substances into a 10 mL stoppered colorimetric tube, add 10 mL of an extraction solvent, vortex at a frequency of 50-60 Hz and a speed of 5400 rpm for 1 min, mix well, and set aside to obtain a sample solution that does not contain thioglycolic acid substances;

[0055] Take 1 mL of the sample solution not containing thioglycolic acid substances, add 1 mL of single standard solutions of thioglycolic acid / isooctyl thioglycolate / butyl thioglycolate of different mass concentrations respectively, mix well, and obtain the sample solution to be tested.

[0056] 3. Test and results

[0057] Add 1 drop of citric acid solution to the above sample solution and shake well; then add 1 drop of ferric chloride hydrochloric acid solution, shake well, and observe the change in solution color.

[0058] The color development of cosmetic samples containing different thioglycolic acid substances is as follows Figure 1 According to the observed color development of thioglycolic acid substances at different concentrations: in the sample solution, the lowest concentration of thioglycolic acid that can be observed as purple or red is 100μg / mL, and the lowest concentration of thioglycolic acid isooctyl thioglycolate or butyl thioglycolate that can be observed as green is 275μg / mL.

[0059] The minimum detection concentration of the rapid detection method of thioglycolic acid substances in cosmetics provided by the present invention is low, which meets the limit detection requirements for thioglycolic acid substances in different cosmetics.

[0060] Experimental Example 2

[0061] In order to explore the stability and specificity (anti-interference ability) of the rapid detection method of thioglycolic acid substances in cosmetics of the present invention, the detection method of the present invention is used to detect cosmetic samples containing interfering substances, comprising the following steps:

[0062] 1. Prepare Reagents

[0063] (1) Extraction solvent: same as in Experimental Example 1.

[0064] (2) Citric acid solution: same as in Experimental Example 1.

[0065] (3) Ferric chloride hydrochloric acid solution: same as in Experimental Example 1.

[0066] (4) Thioglycolic acid single-label solution and interfering substance single-label solution:

[0067] Weigh 0.02g of thioglycolic acid and 0.02g of L-cysteine ​​(interfering substance) in a 10mL volumetric flask, add extraction solvent to dissolve and dilute to scale, shake well, and use them as thioglycolic acid single-label stock solution and L-cysteine ​​single-label stock solution, with a mass concentration of 2000μg / mL; further dilute with extraction solvent to obtain thioglycolic acid single-label solution and L-cysteine ​​single-label solution with a mass concentration of 1000μg / mL, respectively, and store at room temperature. The numbers are marked as:

[0068] Thioglycolic acid single standard solution: S1;

[0069] L-Cysteine ​​single label solution: S2.

[0070] (5) Mixed standard solution of thioglycolic acid and interfering substances:

[0071] Take 5 mL of the single-label stock solution of thioglycolic acid and the single-label stock solution of L-cysteine ​​in the above step (4) respectively in a 10 mL stoppered colorimetric tube, shake well, and obtain a mixed standard solution with a mass concentration of 1000 μg / mL. Store at room temperature and mark it with the number H.

[0072] (6) One sample each of liquid-based cosmetics and cream-based cosmetics that do not contain thioglycolic acid substances.

[0073] 2. Sample Pretreatment

[0074] Weigh 1g of liquid-based and cream-based cosmetic samples that do not contain thioglycolic acid into a 10mL stoppered colorimetric tube, add 10mL of extraction solvent, vortex at a frequency of 50-60Hz and a speed of 5400rpm for 1min, vortex and shake well, and store at room temperature. They are numbered and marked as:

[0075] Liquid-based dosage form without thioglycolic acid substances: Y1;

[0076] Cream dosage form without thioglycolic acid substances: Y2.

[0077] Then, sample solutions 1-8 were prepared according to the following ratios:

[0078] Solution 1: 0.5 mL Y1 + 0.5 mL extraction solvent;

[0079] Solution 2: 0.5 mL Y1 + 0.5 mL S1;

[0080] Solution 3: 0.5 mL Y1 + 0.5 mL S2;

[0081] Solution 4: 0.5 mL Y1 + 0.5 mL H;

[0082] Solution 5: 0.5 mL Y2 + 0.5 mL extraction solvent;

[0083] Solution 6: 0.5 mL Y2 + 0.5 mL S1;

[0084] Solution 7: 0.5 mL Y2 + 0.5 mL S2;

[0085] Solution 8: 0.5 mL Y2 + 0.5 mL H.

[0086] 3. Test and results

[0087] Take 1 mL of each of the sample solutions 1-8 prepared above, add 1 drop of citric acid solution, shake well; then add 1 drop of ferric chloride hydrochloric acid solution, shake well, and observe the color change of the solution;

[0088] This step was repeated at the same time on the first, second and third days. The results are shown in Table 1.

[0089] From the results in Table 1, it can be seen that in different cosmetic sample matrices, the cosmetic sample solutions containing the target analyte thioglycolic acid can all be well colored, but those containing only L-cysteine ​​cannot be colored, so the interference of L-cysteine ​​can be ruled out in real samples. According to the color development results of the experiment repeated at the same time within three days, the color of thioglycolic acid becomes lighter and lighter as time goes by, but it can be effectively colored within three days.

[0090] In summary, the rapid detection method for thioglycolic acid substances in cosmetics provided by the present invention has good specificity and stability.

[0091] Table 1 Results of using the method of the present invention to determine the cosmetic matrix samples containing interfering substances and / or target substances

[0092] serial number Day 1 the next day Day 3 Solution 1 No color No color No color Solution 2 Purple+++ Purple++ Purple+ Solution 3 No color No color No color Solution 4 Purple+++ Red++ Red+ Solution 5 No color No color No color Solution 6 Purple+++ Purple++ Purple+ Solution 7 No color No color No color Solution 8 Purple+++ Purple++ Purple+

[0093] The color depth is divided into + to +++ based on the color observed by the naked eye, from light to dark.

[0094] Experimental Example 3

[0095] In order to explore the influence of different proportions of extraction solvents on the detection results in the rapid detection method of thioglycolic acid substances in cosmetics of the present invention, the following experiment was conducted:

[0096] 1. Prepare Reagents

[0097] (1) Extraction solvent 1: Mix 1 volume part of the standard buffer solution (same as in Experimental Example 1) with 9 volume parts of anhydrous ethanol;

[0098] Extraction solvent 2: Mix 9 parts by volume of the standard buffer solution (same as in Experimental Example 1) with 1 part by volume of anhydrous ethanol.

[0099] (2) Citric acid solution: same as in Experimental Example 1.

[0100] (3) Ferric chloride hydrochloric acid solution: same as in Experimental Example 1.

[0101] 2. Sample Pretreatment

[0102] Weigh 0.1 g of thioglycolic acid reference substance into a 10 mL volumetric flask, add extraction solvents 1 and 2 to dissolve and dilute to the mark, shake well, and the mass concentration is 10000 μg / mL;

[0103] The extracted solutions were further diluted with extraction solvents 1 and 2 to obtain single-label thioglycolic acid solutions with a mass concentration of 500 μg / mL, which were numbered T1 and T2 respectively.

[0104] 3. Test and results

[0105] Take 1 mL of the thioglycolic acid single-label solution T1 and T2 in the above steps respectively in a 10 mL stoppered colorimetric tube, add 1 drop of citric acid solution to each, shake well; then add 1 drop of ferric chloride hydrochloric acid solution, shake well, and observe the color change of the solution. The results are as follows: Figure 2 shown.

[0106] Depend on Figure 2 The results show that when the experimental results of extraction solvent 1 and extraction solvent 2 are compared, when the mixed volume ratio of the standard buffer solution and anhydrous ethanol is changed to 1:9 as the extraction solvent, no obvious color development reaction occurs; while within the extraction solvent range defined by the present invention, an obvious purple-red color can be developed. It can be seen that a specific extraction solvent ratio has a significant effect on the color development result, and only when the extraction solvent ratio is appropriate can a better color development effect be achieved.

[0107] Experimental Example 4

[0108] In order to explore the influence of different concentrations of citric acid solution on the detection results in the rapid detection method of thioglycolic acid substances in cosmetics of the present invention, the following experiment was conducted:

[0109] 1. Prepare Reagents

[0110] (1) Extraction solvent: same as in Experimental Example 1.

[0111] (2) Citric acid solution 1: Weigh 5 g of citric acid monohydrate and dissolve it in 100 mL of water. Shake well.

[0112] (3) Citric acid solution 2: Weigh 1 g of citric acid monohydrate and dissolve it in 100 mL of water. Shake well.

[0113] (4) Citric acid solution 3: Weigh 0.5 g of citric acid monohydrate and dissolve it in 100 mL of water. Shake well.

[0114] (5) Ferric chloride hydrochloric acid solution: same as in Experimental Example 1.

[0115] 2. Sample Pretreatment

[0116] Weigh 0.1 g of thioglycolic acid reference substance into a 10 mL volumetric flask, add extraction solvent to dissolve and dilute to the scale, shake well, and the mass concentration is 10000 μg / mL; further use the extraction solvent to prepare a single standard thioglycolic acid solution with a mass concentration of 500 μg / mL.

[0117] 3. Test and results

[0118] Take 1 mL of the thioglycolic acid single-label solution in the above step into a 10 mL stoppered colorimetric tube, take three portions in parallel, add 1 drop of citric acid solution 1, citric acid solution 2, and citric acid solution 3 to each, shake well; then add 1 drop of ferric chloride hydrochloric acid solution to each, shake well, and observe the color change of the solution. The results are as follows: Figure 3 shown.

[0119] Figure 3 The results show that in the citric acid solution 1 with an excessively high concentration ratio, citric acid completely captures trivalent iron ions, and thioglycolic acid cannot obviously develop color; while the color development effect of the citric acid solution with a mass concentration of about 0.49-1% is good, and the color development color of the low concentration citric acid solution 3 is darker when observed with the naked eye.

[0120] Experimental Example 5

[0121] In order to explore the influence of different concentrations of ferric chloride hydrochloric acid solution on the detection results in the rapid detection method of thioglycolic acid substances in cosmetics of the present invention, the following experiment was conducted:

[0122] 1. Prepare Reagents

[0123] (1) Extraction solvent: same as in Experimental Example 1.

[0124] (2) Citric acid solution: same as in Experimental Example 1.

[0125] (3) Ferric chloride hydrochloric acid solutions of different concentrations:

[0126] ① Dissolve 2.5g of anhydrous ferric chloride in 10mL of concentrated hydrochloric acid, then add 36mL of water and stir thoroughly. The reagent number is C1.

[0127] ② Dilute C1 solution to 2 times. The reagent number is C2.

[0128] ③ Dilute C1 solution to 5 times. The reagent number is C3.

[0129] ④C1 solution is diluted to 10 times. The reagent number is C4.

[0130] ⑤ Dilute C1 solution to 20 times. The reagent number is C5.

[0131] 2. Sample Pretreatment

[0132] Weigh 0.1 g of thioglycolic acid reference substance into a 10 mL volumetric flask, add extraction solvent to dissolve and dilute to the scale, shake well, the mass concentration is 10000 μg / mL, and further use the extraction solvent to prepare a single standard thioglycolic acid solution with a mass concentration of 500 μg / mL.

[0133] 3. Test and results

[0134] Take 1 mL of the thioglycolic acid single-label solution in the above step into a 10 mL stoppered colorimetric tube, take five portions in parallel, add 1 drop of citric acid solution to each, shake well; then add 1 drop of C1, C2, C3, C4, C5 solution to each, shake well, and observe the color change of the solution. The results are as follows: Figure 4 shown.

[0135] Depend on Figure 4 The results showed that the high concentration of ferric chloride hydrochloric acid solution C1-C3 completely consumed the thioglycolic acid substances, and thioglycolic acid could not further combine with divalent iron to develop color; continuing to dilute and reduce the concentration of ferric chloride hydrochloric acid solution, red or purple-red color appeared, and when the dilution multiple reached 20 times, the color turned into a darker purple-red, which was the best effect.

[0136] Example 1

[0137] An embodiment of a method for rapid detection of thioglycolic acid substances in cosmetics according to the present invention, wherein the cosmetics detected in this embodiment are 11 liquid-based cosmetics purchased online; the method for rapid detection of thioglycolic acid substances in this embodiment comprises the following steps:

[0138] 1. Preparation of reagents

[0139] (1) Extraction solvent: 9 parts by volume of standard buffer solution was mixed with 1 part by volume of anhydrous ethanol. The standard buffer solution (pH=10.00) was a commercially available solution (brand: Supeico, main components: boric acid, potassium chloride, sodium hydroxide).

[0140] (2) Citric acid solution: Accurately weigh 0.5 g of citric acid monohydrate and dissolve it in 100 mL of water. Shake well.

[0141] (3) Ferric chloride hydrochloric acid solution: accurately weigh 2.5 g of anhydrous ferric chloride and dissolve it in 10 mL of concentrated hydrochloric acid. Then add 36 mL of water, stir thoroughly to mix, and then dilute 20 times with water.

[0142] 2. Sample Pretreatment

[0143] Weigh 1 g of cosmetic sample into a 10 mL stoppered colorimetric tube, add 10 mL of extraction solvent, vortex at a frequency of 50-60 Hz and a speed of 5400 rpm for 1 min, mix well and set aside to obtain a sample solution.

[0144] 3. Test and results

[0145] Take 1 mL of the sample solution prepared above, add 1 drop of citric acid solution, shake well; then add 1 drop of ferric chloride hydrochloric acid solution, shake well, and observe the color change of the solution. The result is as follows: Figure 2 shown.

[0146] The results obtained using the rapid detection method of the present invention are compared with the results of the statutory inspection standard method. The statutory inspection standard method adopts the high performance liquid chromatography method in Appendix 18 of the Announcement No. 41 of the State Food and Drug Administration in 2023 "Inspection Methods for 8 Raw Materials Including Thioglycolic Acid in Cosmetics". The comparison results are shown in Table 2.

[0147] Depend on Figure 2 From the results in Table 2, it can be seen that: since the detected content of thioglycolic acid in one of the samples was extremely low, lower than the minimum detection concentration of this rapid test method, no detection was achieved. In addition, the test results of other samples were basically consistent with the results of the statutory standard method, and the depth of the observed red or purple-red color well reflected the concentration of thioglycolic acid in the sample: the darker the color, the higher the content; the relative accuracy of the method was 100%, the false negative rate was 0%, and the false positive rate was 0%.

[0148] The samples in this experiment are all commercially available leave-on cosmetics for ordinary skin use. None of the product labels indicate that they contain thioglycolic acid substances. The "Technical Specifications for Safety of Cosmetics" (2015 edition) clearly stipulates that thioglycolic acid and its salts and esters can only be used in perms, hair removal products and rinse-off hair products, and are prohibited from being used in leave-on products for ordinary skin use. According to the test results of this time, the rapid detection method of thioglycolic acid substances of the present invention can realize the rapid discovery of the actual safety risks of illegal addition of thioglycolic acid raw materials in leave-on cosmetics for ordinary skin use, and timely eliminate the possible health and safety hazards to consumers.

[0149] Table 2 Comparison of results of detecting thioglycolic acid substances in 11 cosmetics using the method of the present invention and the standard method

[0150] serial number Sample dosage form Label marking Standard method test results Color development by this method Result determination M1 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 3.1% Purple+++ Positive M2 Liquid base Unlabeled thioglycolic acid substances Not detected No obvious color Negative M3 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 0.29% Light red Positive M4 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 2.0% Purple+++ Positive M5 Liquid base Unlabeled thioglycolic acid substances Not detected No obvious color Negative M6 Liquid base Unlabeled thioglycolic acid substances Not detected No obvious color Negative M7 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 3.8% Purple+++ Positive M8 Liquid base Unlabeled thioglycolic acid substances Not detected No obvious color Negative M9 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 5.0% Purple+++ Positive M10 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 0.019% No obvious color Negative M11 Liquid base Unlabeled thioglycolic acid substances Thioglycolic acid 1.6% Purple+++ Positive

[0151] The color depth is divided into + to +++ based on the color observed by the naked eye, from light to dark.

[0152] Example 2

[0153] The present invention provides an embodiment of a rapid detection method for thioglycolic acid substances in cosmetics. The cosmetics detected in this embodiment are 11 depilatory cream samples purchased online. The steps of the rapid detection method for thioglycolic acid substances in this embodiment are the same as those in Example 1. The results are as follows: Figure 3 shown.

[0154] The results obtained by the rapid detection method of the present invention are also compared with the results of the statutory inspection standard method. The results are shown in Table 3.

[0155] Depend on Figure 3From the results in Table 3, we can see that: since the detected content of thioglycolic acid in one of the samples was extremely low, lower than the minimum detection concentration of this rapid test method, it was not detected. In addition, the test results of other samples were basically consistent with the results of the statutory standard method, and the depth of the observed red or purple-red color well reflected the concentration of thioglycolic acid in the sample: the darker the color, the higher the content; the relative accuracy of the method was 100%, the false negative rate was 0%, and the false positive rate was 0%.

[0156] The samples tested in this embodiment are all commercially available depilatory cream-type cosmetics, and the product labels all indicate that they contain thioglycolates. The rapid detection method for thioglycolates provided by the present invention can effectively detect thioglycolates in depilatory cream samples, thereby achieving preliminary monitoring of the amount of thioglycolates added in depilatory creams and other products.

[0157] The results of the comprehensive experimental examples and Examples 1 and 2 show that the rapid detection method of thioglycolic acid substances provided by the present invention is applicable to cosmetics with different matrices, including water-based preparations, creams, etc., and can cover common cosmetic types on the market that may add thioglycolic acid substances. The present invention can achieve rapid detection of thioglycolic acid substances in cosmetics with high accuracy, can provide effective technical support for the detection needs of on-site detection scenarios such as supervision and inspection, has strong practicality, and has high application value.

[0158] Table 3 Comparison of results of detecting thioglycolic acid substances in 11 depilatory creams using the method of the present invention and the standard method

[0159] serial number Sample dosage form Label marking Standard method test results Color development by this method Result determination Q1 Cream Labelled to contain potassium thioglycolate Thioglycolic acid 3.0% Purple+++ Positive Q2 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 2.8% Purple+++ Positive Q3 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 0.24% No obvious color Negative Q4 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 1.4% Purple++ Positive Q5 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 2.3% Purple+++ Positive Q6 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 2.8% Purple+++ Positive Q7 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 1.6% Purple+++ Positive Q8 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 1.6% Purple+++ Positive Q9 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 1.8% Purple+++ Positive Q10 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 3.1% Purple+++ Positive Q11 Cream Labelled to contain calcium thioglycolate Thioglycolic acid 1.9% Purple+++ Positive

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A rapid detection method for thioglycolic acid substances in cosmetics, characterized in that: The following steps are involved: (1) mixing the cosmetics in an extraction solvent to obtain a sample solution; The extraction solvent is a mixture of a standard buffer solution and anhydrous ethanol, the pH of the standard buffer solution is 9.9-10.1, and the volume ratio of the standard buffer solution to anhydrous ethanol is (8-10):1; (2) adding citric acid solution to the sample solution and mixing, then adding ferric chloride hydrochloric acid solution and mixing, observing the color and obtaining the result, thereby completing the rapid detection of thioglycolic acid substances in the cosmetics; The mass ratio of citric acid in the citric acid solution to ferric chloride in the ferric chloride hydrochloric acid solution is (0.49-1):(0.24-0.25).

2. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (1), the ratio of the mass of the cosmetic to the volume of the extraction solvent is (0.5-1) g:10 mL.

3. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (1), the mixing method is vortexing or shaking.

4. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (1), the components of the standard buffer solution include boric acid, potassium chloride and sodium hydroxide.

5. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (1), the volume ratio of the standard buffer solution to anhydrous ethanol is 9:

1.

6. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (2), the volume ratio of the sample solution, the citric acid solution and the ferric chloride solution is sample solution: citric acid solution: ferric chloride solution = (1-2): (0.03-0.05): (0.03-0.05).

7. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 6, characterized in that: In the step (2), the citric acid solution is obtained by dissolving 0.5-1 g of citric acid monohydrate in 100 mL of water and mixing.

8. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 6, characterized in that: In the step (2), the ferric chloride solution is prepared by dissolving 2.5 g of anhydrous ferric chloride in 10 mL of concentrated hydrochloric acid, adding 36 mL of water, mixing, and diluting by 20 times.

9. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 1, characterized in that: In the step (2), The color is red or purple, and the result is that the cosmetic contains thioglycolic acid or thioglycolate; The color is green, and the result is that the cosmetic contains isooctyl thioglycolate or butyl thioglycolate.

10. The rapid detection method of thioglycolic acid substances in cosmetics according to claim 9, characterized in that: In the sample solution, the detection concentration of the thioglycolic acid is 100 μg / mL, and the detection concentrations of isooctyl thioglycolate and butyl thioglycolate are 275 μg / mL.

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