1. A method for detecting distearyldimethylammonium chloride (DSDMAC) in cosmetics is characterized in that: the detection method is a detection method for analyzing by connecting a high performance liquid chromatography with an evaporative light scattering system, wherein the high performance liquid chromatography adopts a surfactant column.

2. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic composition according to claim 1, wherein the method specifically comprises the steps of:

s1: dissolving a sample, adding sodium chloride and acetonitrile, oscillating, centrifuging, and taking supernatant to obtain a sample solution to be detected;

s2: making a standard curve by adopting an external standard method;

s2-1: preparing a series of standard working solutions;

s2-2: respectively analyzing and detecting each standard working solution by a high performance liquid chromatography-tandem evaporative light scattering detection system to obtain the corresponding peak areas of the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride under various concentrations, wherein the analysis conditions are as follows:

a chromatographic column: a surfactant column;

mobile phase: adopting a mixed mobile phase, wherein the mobile phase A is 100mmol/L ammonium acetate aqueous solution, and the mobile phase B is acetonitrile;

elution procedure: adopting a gradient elution mode;

temperature of the column: 30 ℃;

the evaporation temperature of the evaporation light detector is 40 ℃, the temperature of the atomizer is 45 ℃, the atomizing gas is nitrogen, and the flow rate of the carrier gas is 1.5 SLM;

s2-3: establishing a standard curve by taking the concentration of DSDMAC in the standard working solution as a horizontal coordinate and taking the sum of peak areas corresponding to the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride under corresponding concentrations as a vertical coordinate;

s3: analyzing and detecting the sample solution to be detected obtained in the step S1 by adopting the same detection system and monitoring conditions;

s4: and (4) bringing the sum of the peak areas corresponding to the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride in the analysis result obtained in the step (S3) into the standard curve prepared in the step (S2), and further obtaining the corresponding concentration of DSDMAC.

3. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the ratio of the sample aqueous solution to the added sodium chloride is 5mL:3g of the total weight.

4. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the ratio of the sample to the added acetonitrile is 1g:10 mL.

5. The method of detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein when the sample is a sparingly soluble sample, the sample is dispersed by ultrasound, and then sodium chloride and acetonitrile are added.

6. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the oscillation frequency is 160 r/min; further preferably, the oscillation time is 30 min.

7. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the pH of the mobile phase a is 5.5.

8. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the gradient elution procedure is 0.0 to 10.0min, 30% A to 5% A, 10.0 to 15.0min, 5% A, 15.0 to 16.0min, 5% A to 30% A, 16.0 to 20min, 30% A.

9. The method for detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic according to claim 2, wherein the retention time of each compound of the DSDMAC in a high performance liquid chromatography tandem evaporative light scattering system chromatogram is respectively 8.367min for dicetyldimethylammonium chloride, 9.694min for hexadecyloctadecyldimethylammonium chloride and 11.171min for dioctadecyldimethylammonium chloride.

10. The method of detecting distearyldimethylammonium chloride (DSDMAC) in a cosmetic product of claim 9 wherein the standard curve is: y 6.037 x-7.512.

Background

Distearyldimethylammonium Chloride (DSDMAC) is a quaternary ammonium cationic surfactant, generally composed of a mixture of alkyl dimethylammonium chlorides with carbon chain lengths of sixteen and eighteen. DSDMAC is mainly used as an antistatic agent, an emulsifier and a softener in cosmetics and mainly comprises three compounds of dicetyl dimethyl ammonium chloride, hexadecyl octadecyl dimethyl ammonium chloride and dioctadecyl dimethyl ammonium chloride.

At present, researches show that DSDMAC has certain irritation to skin, and particularly has the greatest irritation to sensitive and delicate skin around eyes, and ecotoxicology research results show that DSDMAC is one of allergen inducing allergy. Its median Lethal Concentration (LC) to fish₅₀) (48-96 hours of action) is 0.6-2.6 mg/L.

Therefore, the detection, especially the quantitative detection, of DSDMAC in the cosmetics is of great significance.

Disclosure of Invention

The invention aims to solve the technical problem of providing a reliable DSDMAC detection method, thereby providing technical support for quality safety supervision of cosmetics and providing technical guarantee for body health safety of the public.

In order to solve the technical problem, the invention discloses a detection method of DSDMAC in cosmetics, which is a detection method for analyzing by a high performance liquid chromatography-evaporative light scattering system in series, wherein the high performance liquid chromatography adopts a surfactant column.

The invention further discloses that the detection method specifically comprises the following steps:

s1: dissolving a sample, adding sodium chloride and acetonitrile, oscillating, centrifuging, and taking supernatant to obtain a sample solution to be detected;

s2: making a standard curve by adopting an external standard method;

s2-1: preparing a series of standard working solutions;

s2-2: respectively analyzing and detecting each standard working solution by a high performance liquid chromatography-tandem evaporative light scattering detection system to obtain the corresponding peak areas of the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride under various concentrations, wherein the analysis conditions are as follows:

a chromatographic column: a surfactant column;

mobile phase: adopting a mixed mobile phase, wherein the mobile phase A is 100mmol/L ammonium acetate aqueous solution, and the mobile phase B is acetonitrile;

elution procedure: adopting a gradient elution mode;

temperature of the column: 30 ℃;

the evaporation temperature of the evaporation light detector is 40 ℃, the temperature of the atomizer is 45 ℃, the atomizing gas is nitrogen, and the flow rate of the carrier gas is 1.5 SLM;

s2-3: establishing a standard curve by taking the concentration of DSDMAC in the standard working solution as a horizontal coordinate and taking the sum of peak areas corresponding to the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride under corresponding concentrations as a vertical coordinate;

s3: analyzing and detecting the sample solution to be detected obtained in the step S1 by adopting the same detection system and monitoring conditions;

s4: bringing the sum of peak areas corresponding to the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride in the analysis result obtained in the step S3 into the standard curve prepared in the step S2, and further obtaining the corresponding concentration of DSDMAC;

wherein the step S2 is not in sequence with the step S3. That is, the standard curve may be calculated first, and then the concentration of the sample to be detected may be measured, or the detection value of the sample to be detected may be recorded first, and then the concentration of the sample to be detected may be obtained after the standard curve is calculated.

Further preferably, the ratio of the sample aqueous solution to the added sodium chloride is 5mL:3 g.

Preferably, the ratio of sample to added acetonitrile is 1g:10 mL.

In a preferred technical scheme, when the sample is a sample which is difficult to dissolve, the sample is dispersed by using ultrasonic, and then sodium chloride and acetonitrile are added.

Further preferably, the oscillation frequency is 160 r/min. Further preferably, the oscillation time is 30 min.

In a preferred embodiment, the pH of the mobile phase a is 5.5.

As a preferred technical scheme, the gradient elution procedure is 0.0-10.0 min, 30-5% A, 10.0-15.0 min, 5% A, 15.0-16.0 min, 5-30% A, 16.0-20 min and 30% A.

Further preferably, the retention time of each compound of DSDMAC in a chromatogram of a high performance liquid chromatography-tandem evaporative light scattering system is 8.367min, 9.694min and 11.171min respectively.

Further preferably, the standard curve is: y 6.037 x-7.512.

By adopting the technical scheme disclosed by the invention, the detection of DSDMAC in cosmetics with different textures can be realized. The invention establishes various conditions and parameters in the method for accurately detecting DSDMAC in cosmetics with different textures through a great deal of complicated creative labor, and the conditions and the parameters comprise but are not limited to the selection of an extraction solvent and the determination of volume in a process in pretreatment, the determination of oscillation frequency and time, the selection of a chromatographic column in detection and analysis, the selection of a mobile phase, particularly the selection and the determination of an ammonium acetate aqueous solution mobile phase, the concentration and pH conditions of the ammonium acetate aqueous solution mobile phase and the like. The verification proves that the recovery rate and the precision data of the detection method disclosed by the invention both accord with the technical index of residue analysis, and the detection method is a reliable detection method for DSDMAC in cosmetics.

Drawings

FIG. 1 is a chromatogram of a sample of the emulsion of example 3.

Detailed Description

In order that the invention may be better understood, we now provide further explanation of the invention with reference to specific examples.

The chemical information of the compounds involved in the invention is as follows:

example 1

Preparing a standard working solution: accurately weighing a certain amount of DSDMAC standard substance, dissolving with methanol, fixing the volume to 10mL, preparing a standard stock solution with the mass concentration of 1000mg/L, transferring a certain volume of the standard stock solution, and preparing a standard working solution with the concentration of 200 mg/L.

Diluting the standard working solution step by step into the following concentrations: 0. 10, 20, 50, 100 and 200mg/L series of standard working solutions.

Analyzing and detecting each standard working solution by a high performance liquid chromatography-tandem evaporative light scattering detection system to obtain peak areas corresponding to the dicetyl dimethyl ammonium chloride, the hexadecyl octadecyl dimethyl ammonium chloride and the dioctadecyl dimethyl ammonium chloride under each concentration, wherein the analysis conditions are as follows:

a chromatographic column: a surfactant column;

mobile phase: adopting a mixed mobile phase, wherein the mobile phase A is 100mmol/L ammonium acetate aqueous solution, and the mobile phase B is acetonitrile;

elution procedure: adopting a gradient elution mode;

temperature of the column: 30 ℃;

the evaporation temperature of the evaporation light detector is 40 ℃, the temperature of the atomizer is 45 ℃, the atomizing gas is nitrogen, and the flow rate of the carrier gas is 1.5 SLM;

the retention time of each compound of DSDMAC in a chromatogram of a high performance liquid chromatography-tandem evaporation light scattering system is 8.367min, 9.694min and 11.171min respectively;

and calculating to obtain a standard curve equation, wherein y is 6.037 x-7.512.

Example 2

According to the invention, a known amount of DSDMAC is added into a negative sample, and the detection accuracy of the cosmetic with different textures is verified through the standard addition recovery rate and the relative standard deviation.

According to different cosmetic textures, different sample pretreatment modes are respectively selected and prepared into sample solutions to be detected.

1. Sample pretreatment

(1) Oily, powdery, cream and lotion samples

Weighing 1.0g (accurate to 0.01g) of sample in a 50mL centrifuge tube, adding 5mL of aqueous solution, dispersing the sample by ultrasonic, adding 3g of sodium chloride and 10mL of acetonitrile, extracting for 30min by oscillation at the oscillation frequency of 160r/min, centrifuging for 5min at 8000r/min, absorbing part of supernatant, filtering by an organic phase needle type filter head to a sample injection bottle, and determining by a high performance liquid chromatograph.

(2) Liquid water-based sample

Weighing 1.0g (accurate to 0.01g) of sample in a 50mL centrifuge tube, adding 4mL of water, 3g of sodium chloride and 10mL of acetonitrile, extracting for 30min by oscillation at the oscillation frequency of 160r/min, centrifuging for 5min at 8000r/min, absorbing part of supernatant, filtering to a sample injection bottle through an organic phase needle type filter head, and determining by using a high performance liquid chromatograph.

2. Conditions of instrumental analysis

A chromatographic column: a Surfactant column (Acclaim Surfactant, 5 μm, 4.6 mm. times.150 mm, Thermo Co., USA); mobile phase: a-100mmol/L aqueous ammonium acetate solution (pH 5.5), B-acetonitrile, gradient elution procedure: 0.0-10.0 min, 30-5% A, 10.0-15.0 min, 5% A, 15.0-16.0 min, 5-30% A, 16.0-20 min, 30% A; temperature of the column: 30 ℃; the sample injection amount is 10 mu L; the flow rate was 1.0 mL/min. The evaporation temperature of the evaporation light detector is 40 ℃, the temperature of the atomizer is 45 ℃, the atomizing gas is nitrogen, and the flow rate of the carrier gas is 1.5 SLM.

The results are shown in Table 1;

table 1: normalized recovery and relative standard deviation of DSDMAC in negative samples

As can be seen from the results in Table 1, within the range of the addition level of (100-1000) mg/kg, the average recovery rate of DSDMAC in the oily, powdery, cream and emulsion samples is 82.5-98.4%, and the RSD value is not more than 6.3%; the average recovery rate of DSDMAC in the liquid water-based sample is 95.1-100.9%, and the RSD value is not more than 5.2%.

The recovery rate and precision data of the method both accord with the technical index of residue analysis, and the method is accurate.

Example 3

Weighing 1.0g (accurate to 0.01g) of emulsion sample in a 50mL centrifuge tube, adding 5mL of aqueous solution, dispersing the sample by ultrasonic, adding 3g of sodium chloride and 10mL of acetonitrile, extracting for 30min by oscillation at the oscillation frequency of 160r/min, centrifuging for 5min at 8000r/min, absorbing part of supernatant, filtering by an organic phase needle type filter head to a sample injection bottle, and determining by a high performance liquid chromatograph.

The detection analysis was carried out according to the following conditions:

a chromatographic column: a Surfactant column (Acclaim Surfactant, 5 μm, 4.6 mm. times.150 mm, Thermo Co., USA); mobile phase: a-100mmol/L aqueous ammonium acetate solution (pH 5.5), B-acetonitrile, gradient elution procedure: 0.0-10.0 min, 30-5% A, 10.0-15.0 min, 5% A, 15.0-16.0 min, 5-30% A, 16.0-20 min, 30% A; temperature of the column: 30 ℃; the sample injection amount is 10 mu L; the flow rate was 1.0 mL/min. The evaporation temperature of the evaporation light detector is 40 ℃, the temperature of the atomizer is 45 ℃, the atomizing gas is nitrogen, and the flow rate of the carrier gas is 1.5 SLM.

Results and analysis:

the chromatogram of the obtained sample of the emulsion is shown in FIG. 1, and the sample chromatogram has chromatographic peaks at 8.367min, 9.694min and 11.171min as can be seen from the combination of FIG. 1, which indicates that the sample of the emulsion contains DSDMAC.

The areas of the three peaks were then summed to give a total area of 583.3.

According to the standard curve equation, y is 6.037x-7.512, and y is 583.3, resulting in x being 97.865 mg/kg.

What has been described above is a specific embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.