Method for detecting quaternary ammonium salt compounds in infant products and application thereof

Abstract

This invention discloses a method and application for detecting quaternary ammonium compounds in infant and toddler products, belonging to the field of quaternary ammonium analysis and detection technology. The method involves first mixing a sample of the infant and toddler product with a recovery indicator and adding it to a centrifuge tube for extraction, then combining the extracts. The combined extracts are then concentrated, redissolved in methanol, and concentrated again to obtain a concentrated extract. This concentrated extract is then centrifuged and collected. Finally, the centrifuged extract is mixed with an internal standard, and the quaternary ammonium compounds are quantitatively analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry. This invention enables the simultaneous detection of multiple types of quaternary ammonium compounds in infant and toddler products, is convenient to process, has a short analysis time, and low cost, maximizing analytical efficiency and achieving higher sensitivity and better reproducibility while avoiding matrix effects.

Description

Technical Field

[0001] This invention belongs to the field of quaternary ammonium salt analysis and detection technology, specifically a method and application for detecting quaternary ammonium salt compounds in infant products. Background Technology

[0002] Quaternary ammonium compounds (QACs) are a class of cationic surfactants with a permanent positive charge, commonly used for disinfection, antibacterial, antistatic, and antifungal purposes. They are widely found in consumer products such as baby wipes, laundry detergents, antibacterial coatings on toys, baby bedding, and clothing. Because infants' skin barrier function is not fully developed, long-term or high-concentration exposure to quaternary ammonium compounds may cause skin irritation, allergic reactions, and even potential systemic health risks. Therefore, the detection of these substances in infant products is of great significance.

[0003] Currently, there are few detection technologies for QACs (quaternary ammonium salts) compounds. For example, Chinese patent application CN109633036A discloses a method for detecting benzalkonium chloride in wet wipes. This method utilizes ultra-high performance liquid chromatography-ultraviolet detection (UPLC-UV) for quantitative analysis of benzalkonium chloride in wet wipes, and can, to some extent, detect single quaternary ammonium salt compounds in wet wipes. However, existing technologies still have the following shortcomings:

[0004] 1. Limitations of testing targets: Existing patented methods are mainly for single-type samples such as wet wipes, and lack adaptability to a variety of complex matrices in infant and toddler products (such as textiles, plastics, liquid care products, etc.).

[0005] 2. Insufficient selectivity: When multiple quaternary ammonium salt compounds coexist, UPLC-UV detection is prone to overlapping or interference of chromatographic peaks, making it difficult to achieve accurate separation and quantification of multiple components.

[0006] 3. Limited sensitivity: The detection limit of the ultraviolet detector is relatively high, and the detection sensitivity is insufficient for quaternary ammonium salt compounds that are present at low concentrations or in trace amounts.

[0007] 4. Lack of unified standards: Currently, there are no unified standards for the limits of quaternary ammonium compounds in infant and toddler products, and the comparability of test results between different laboratories is poor.

[0008] Therefore, there is an urgent need for a detection method that is applicable to the complex matrices of various infant and toddler products, can simultaneously detect multiple types of quaternary ammonium compounds, and has high sensitivity and selectivity, in order to meet the needs of product safety supervision and risk assessment. Summary of the Invention

[0009] The purpose of this invention is to provide a method and application for the detection of quaternary ammonium compounds in infant products. This method can achieve efficient extraction, separation and accurate quantification of various QACs in complex matrices, with low detection limits, good repeatability and simple operation, thus meeting the safety testing requirements of infant products.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A method for detecting quaternary ammonium compounds in infant and toddler products, comprising the following steps:

[0012] Step 1: Mix the sample of infant products with the recovery indicator and add it to a centrifuge tube, then perform the extraction operation and combine the extracts;

[0013] Step 2: Concentrate the combined extracts, redissolve them in methanol, and then concentrate them again to obtain a concentrated extract. Centrifuge and collect the centrifuged extract.

[0014] Step 3: Mix the centrifuged extract with the internal standard, and perform quantitative analysis of quaternary ammonium compounds using ultra-high performance liquid chromatography-tandem mass spectrometry.

[0015] Furthermore, the ratio of sample to recovery indicator was 0.2 g: 10 ng.

[0016] Furthermore, the recovery indicator was obtained by mixing benzyl dimethyl dodecyl ammonium-d7 chloride and benzyl dimethyl tetradecyl ammonium-d7 chloride in a 1:1 mass ratio. The internal standard was phosmet-d10.

[0017] Furthermore, samples of infant and toddler products include fiber-containing samples and liquid samples.

[0018] Furthermore, fiber-containing samples include, but are not limited to, consumer products such as infant clothing, diapers, and wipes that contain at least one layer of nonwoven fabric, fiber web, or cotton textile.

[0019] The extraction procedure for samples containing fiber is as follows:

[0020] Add the extraction solvent to the centrifuge tube, sonicate for 15 min, and centrifuge at 2500 rpm for 5 min. Repeat the extraction twice. Then add acetonitrile to the extracted fiber-containing sample, sonicate for 15 min, and centrifuge at 2500 rpm for 5 min. Repeat the extraction twice. Combine the four extracts.

[0021] The centrifugation conditions for fiber-containing samples were as follows: the concentrated extract was transferred to a 0.2 μm nylon microcentrifuge filter rinsed with methanol and centrifuged at 6000 rpm for 3 min.

[0022] Furthermore, liquid samples include, but are not limited to, liquid personal care products such as lotions and shower gels.

[0023] The extraction procedure for liquid samples is as follows:

[0024] Add the extraction solvent to the centrifuge tube, sonicate for 15 minutes, centrifuge at 2500 rpm for 5 minutes, repeat the extraction four times, and then combine the extracts.

[0025] The conditions for centrifuging the liquid sample were as follows: the concentrated extract was frozen at -80℃ for 6 hours and centrifuged at -10℃ and 13000 rpm for 5 minutes.

[0026] Furthermore, the extractant is a mixture of n-hexane and dichloromethane in a volume ratio of 1:1.

[0027] This invention also provides an application of a method for detecting quaternary ammonium compounds in infant products in complex matrices.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention provides a high-throughput and convenient method for detecting and analyzing quaternary ammonium compounds in infant and toddler products. This method can simultaneously detect multiple types of quaternary ammonium compounds in infant and toddler products, with convenient pretreatment, short analysis time, low cost, and can maximize the analysis efficiency.

[0030] 2. In the pretreatment of baby lotion and washing products in this invention, the extract is blown down to 0.1 mL, reconstituted with methanol, and then frozen to allow lipids to precipitate. Then, it needs to be centrifuged at low temperature in a refrigerated centrifuge to allow lipid precipitation to facilitate the transfer of the supernatant, thereby achieving the purpose of removing lipids, reducing matrix effect, and thus improving the spiked recovery rate.

[0031] 3. This invention uses ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) for quantitative analysis of quaternary ammonium salt compounds. The MRM mode is used for quantitative analysis, which can achieve higher sensitivity (detection limit reaches ng / g) and better reproducibility while avoiding matrix effects. Attached Figure Description

[0032] Figure 1 This is a comparison chart of the recovery rates of Example 1 and Comparative Example 1 when the spiked amount is 1 ng.

[0033] Figure 2 This is a comparison chart of the recovery rates of Example 1 and Comparative Example 1 of the present invention when the spiked amount is 10 ng. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: A method for detecting quaternary ammonium compounds in infant and toddler products, specifically for analyzing quaternary ammonium compounds in infant and toddler clothing, diapers, wipes, lotions, and toiletries:

[0036] 1. Sample collection:

[0037] I purchased 36 baby clothes, 38 kinds of baby wipes, 30 kinds of baby diapers, 37 kinds of baby care products (lotion), and 24 kinds of bath products (body wash) from e-commerce platforms.

[0038] 2. Sample pretreatment:

[0039] (1) Pretreatment method for clothing (i.e., fiber-containing samples):

[0040] ① After cutting the clothing into small pieces, weigh out 0.20g (accurate to 0.01g) and place it in a 15mL PP centrifuge tube. Add the recovery indicator as follows:

[0041] 10 ng of benzyl dimethyl dodecyl ammonium-d7 chloride and 10 ng of benzyl dimethyl tetradecyl ammonium-d7 chloride.

[0042] ② Add 3 mL of extraction solvent (a 1:1 volume ratio of hexane and dichloromethane) to the centrifuge tube. Sonicate for 15 min, then centrifuge at 2500 rpm for 5 min. Repeat this process twice, then combine the extracts. Next, add 3 mL of acetonitrile to the extracted sample, sonicate for 15 min, then centrifuge at 2500 rpm for 5 min. Repeat this extraction process twice more, then combine the extracts.

[0043] ③ The combined extract was concentrated under a gentle nitrogen flow to 0.1 mL. Then 1 mL of methanol was added and the mixture was concentrated to 0.1 mL to obtain the concentrated extract.

[0044] ④ Rinse the 0.2µm nylon microcentrifuge filter three times with methanol, transfer the concentrated extract into the filter, and centrifuge at 6000rpm for 3min.

[0045] ⑤ Transfer the extract after freezing and centrifugation to a vial (with a liner), add 10 ng of internal standard phosmet-d10, and then use liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) to quantitatively analyze the environmental pollutants.

[0046] The pretreatment methods for wet wipes and diapers are the same as those for clothing.

[0047] (2) Pretreatment method for nursing products (lotion, i.e., liquid sample):

[0048] ① Weigh 0.20g of lotion (accurate to 0.01g) and place it in a 15mL PP centrifuge tube. Add the recovery indicator as follows:

[0049] 10 ng of benzyl dimethyl dodecyl ammonium-d7 chloride and 10 ng of benzyl dimethyl tetradecyl ammonium-d7 chloride.

[0050] ② Add 3 mL of extraction solvent (a 1:1 volume ratio of hexane and dichloromethane) to a centrifuge tube. Sonicate for 15 min, then centrifuge at 2500 rpm for 5 min. Repeat the above steps four times, and then combine the extracts.

[0051] ③ Concentrate the combined extract to 0.1 mL under a gentle nitrogen flow, add 1 mL of methanol, and continue to concentrate to 0.1 mL under nitrogen to obtain a concentrated extract.

[0052] ④ Rinse the 0.2µm nylon microcentrifuge filter three times with methanol, transfer the concentrated extract into the filter, freeze at -80℃ for at least 6 hours, and then centrifuge at -10℃ and 13000rpm for 5 minutes.

[0053] ⑤ Transfer the extract after freezing and centrifugation to a vial (with a liner), add 10 ng of internal standard phosmet-d10, and then use ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) to quantitatively analyze the environmental pollutants.

[0054] The pretreatment method for bath products (shower gel) is the same as that for skin care products (moisturizer).

[0055] 3. Instrumental analysis:

[0056] All pretreated samples were subjected to ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS). The liquid chromatography methods are shown in Table 2. The mass spectrometry conditions included: electrospray ionization source, voltage 4500V, ion source temperature 500℃, detection mode positive ion mode; nebulizer gas pressure: nitrogen pressure 30psi, auxiliary heating gas pressure: nitrogen pressure 40psi; the specific ion pair parameters and mass spectrometry parameters for multiple reaction monitoring (MRM) mode are shown in Table 1.

[0057] Table 1. Specific information about the compounds

[0058]

[0059] Table 2 Information on liquid phase methods for compounds

[0060]

[0061] 4. Quality Assurance and Quality Control:

[0062] Quality assurance and quality control included testing for the recovery of procedural blanks and recovery indicators, as well as testing of mixed matrix spiked samples. Two laboratory procedural blanks were processed for every 10 samples, with anhydrous sodium sulfate used as a substitute for the blanks; the processing procedure was identical to that of the actual samples. The recoveries of the recovery indicators for all samples were calculated using AB Sciex 5500 Q Trap triple quadrupole-linear ion trap mass spectrometer software Analyst 1.6.3, and the results showed a recovery rate of 70-110%.

[0063] Spiked samples in mixed matrix: Samples of baby clothes, wipes, diapers, lotion, and toiletries were mixed separately. Two samples of each type were taken after mixing, for a total of 10 samples. Standards were added to three samples, with 1 ng of standard added to the other three samples and 10 ng of standard added to the other three samples.

[0064] The added standards include the following compounds: (benzyl dimethyl octyl ammonium chloride (C8-BAC), N-decyl-N,N-dimethyl benzyl ammonium chloride (C10-BAC), dodecyl dimethyl benzyl ammonium chloride (C12-BAC), tetradecyl dimethyl benzyl ammonium chloride (C14-BAC), hexadecyl dimethyl benzyl ammonium chloride (C16-BAC), octadecyl dimethyl benzyl ammonium chloride (C18-BAC), octyl trimethyl ammonium chloride (C8-ATMAC), decadecyl trimethyl ammonium bromide (C10-ATMAC), dodecyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C8-ATMAC), octyl trimethyl ammonium bromide (C10-ATMAC), octyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C14-BAC), octyl trimethyl ammonium chloride (C16-BAC), octyl trimethyl ammonium chloride (C18-BAC), octyl trimethyl ammonium chloride (C8-ATMAC), octyl trimethyl ammonium bromide (C10-ATMAC), octyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C12-BAC), octyl trimethyl ammonium chloride (C14-BAC), octyl trimethyl ammonium chloride (C15-BAC), octyl trimethyl ammonium chloride (C16-BAC), octyl trimethyl ammonium chloride (C18-BAC), octyl trimethyl ammonium chloride (C10-ATMAC), octyl trimethyl ammonium chloride ( -ATMAC), tetradecyltrimethylammonium chloride (C14-ATMAC), hexadecyltrimethylammonium chloride (C16-ATMAC), octadecyltrimethylammonium chloride (C18-ATMAC), dimethyl dioctylammonium bromide (C8-DDAC), didecyl dimethylammonium bromide (C10-DDAC), didodecyl dimethylammonium bromide (C12-DDAC), ditetradecyl dimethylammonium bromide (C14-DDAC), dihexadecyl dimethylammonium bromide (C16-DDAC), dioctadecyl dimethylammonium bromide (C18-DDAC)).

[0065] The spiked samples were pretreated in the same way as in steps (1) and (2) of step 2 above. The average recovery and matrix effect of the target compounds were calculated by integral calculation using Analyst 1.6.3 software of AB Sciex5500 Q Trap triple quadrupole-linear ion trap mass spectrometer: the average recovery of all target compounds ranged from 69 to 114%, and the matrix effect ranged from 90 to 115%.

[0066] For each class of compounds, quantification was performed using standard curves at five or more concentration levels, with a correlation coefficient greater than 0.995. The limit of quantification (LOQ) was defined as the compound concentration corresponding to a response that was 3 or 10 times the standard deviation of the noise. If the calculated LOQ was lower than the background contamination value in the blank, the highest blank concentration was used as the LOQ. The LOQs for the target compounds are shown in Table 1.

[0067] 5. Results Analysis:

[0068] Analysis of the test results of 18 quaternary ammonium compounds in five categories of consumer products, including clothing, diapers, wet wipes, shower gel, and lotion, revealed that these compounds are widely present in consumer products, and their distribution patterns show a specificity closely related to the product type.

[0069] Overall, among baby products, baby wipes showed a detection rate of 8 compounds exceeding 50%, with 7 of them exceeding 70%. Clothing and body wash followed, with 9 and 8 compounds respectively exceeding 50% detection rates. Diapers and lotions showed fewer frequently detected compounds, with only 4 and 3 respectively. In some products, specific compounds were even universally detected; for example, C12-BAC and C16-DDAC in clothing, C12-BAC, C14-BAC, and C10-DDAC in baby wipes, and C16-DDAC in body wash all had a 100% detection rate, indicating that they may exist as commonly used ingredients or common residues in these product systems.

[0070] In terms of residual concentration, wet wipes also exhibited the highest contamination levels among product categories. The median concentrations of C12-BAC and C14-BAC were 651.76 ng / g and 2740.41 ng / g, respectively, with maximum values ​​reaching 14794.89 ng / g and 9963.66 ng / g, indicating that these compounds are not only prevalent in wet wipes but also present in high levels. The median concentration of C16-DDAC in clothing was 1396.80 ng / g, also at a relatively high level. Furthermore, although few compounds were frequently detected in lotions, the concentration range of C18-ATMC in some samples was extremely wide, with an upper limit as high as 60324.93 ng / g, suggesting a potential high point-source exposure risk due to specific formulations in this product. Overall, the residual characteristics of different types of quaternary ammonium salts showed significant differences: ATMC homologues were generally detected more frequently and had higher median values ​​in shower gels, while BAC homologues showed the most prominent residues in wet wipes.

[0071] This invention demonstrates that quaternary ammonium compounds are commonly found in various everyday consumer products, particularly wet wipes, clothing, and shower gels, and their distribution is closely related to product use and composition. Wet wipes showed the highest detection rate and residue concentration, suggesting that they may be a significant source of human exposure to quaternary ammonium compounds through skin contact, warranting close attention in subsequent exposure assessments and health risk studies.

[0072] Table 3. Detection of Quaternary Ammonium Compounds in Baby Products

[0073]

[0074] Comparative Example 1: Samples were collected according to the collection method in step 2 of Example 1. Samples of baby clothing, wet wipes, diapers, lotion, and shower gel were mixed separately. Two samples of each type were taken, for a total of 10 samples, each weighing 0.20g (accurate to 0.01g). Standards were added to three samples (1ng each) and the other three (10ng each). The added standards included the following compounds: (benzyl dimethyl octyl ammonium chloride (C8-BAC), N-decyl-N,N-dimethyl benzyl ammonium chloride (C10-BAC), dodecyl dimethyl benzyl ammonium chloride (C12-BAC), tetradecyl dimethyl benzyl ammonium chloride (C14-BAC), hexadecyl dimethyl benzyl ammonium chloride (C16-BAC), octadecyl dimethyl benzyl ammonium chloride (C18-BAC), octyl trimethyl ammonium chloride (C8-ATMAC), decadecyl trimethyl ammonium bromide (C10-ATMAC), dodecyl trimethyl ammonium chloride (C12-BAC), and octyl trimethyl ammonium chloride (C12-BAC). -ATMAC), tetradecyltrimethylammonium chloride (C14-ATMAC), hexadecyltrimethylammonium chloride (C16-ATMAC), octadecyltrimethylammonium chloride (C18-ATMAC), dimethyl dioctylammonium bromide (C8-DDAC), didecyl dimethylammonium bromide (C10-DDAC), didodecyl dimethylammonium bromide (C12-DDAC), ditetradecyl dimethylammonium bromide (C14-DDAC), dihexadecyl dimethylammonium bromide (C16-DDAC), dioctadecyl dimethylammonium bromide (C18-DDAC). Then, perform the following detection method:

[0075] (1) For clothing / wet wipes: After cutting into small pieces, add 5 mL of methanol, vortex and sonicate for 20 min. For shower gel / moisturizer: Add 5 mL of methanol directly, vortex to mix, and sonicate for 20 min.

[0076] (2) Add 5 mL of 20 mM ammonium formate solution (pH=3.5) to the methanol extract and vortex to mix. Centrifuge at 10000 rpm for 10 min and collect the supernatant for later use;

[0077] (3) Add 3 mL of methanol to the WCX column (Waters Oasis WCX solid phase extraction column / SPE column 6cc / 150mg), and allow it to drip naturally to wet the stationary phase. Then add 3 mL of ultrapure water, and allow it to drip naturally as well.

[0078] (4) Add 3 mL of 20 mM ammonium formate solution (pH=3.5) and let the solution drip down to the top of the extraction column bed;

[0079] (5) Pass all the prepared sample supernatant slowly through the equilibrated WCX column at a flow rate of 1 mL / min;

[0080] (6) Add 3 mL of 20 mM ammonium formate solution (pH=3.5) to the column, let it drip naturally, add 3 mL of methanol, rinse, and then dry the column bed under strong vacuum (10 psi) for 5-10 min;

[0081] (7) Add 3 mL of 5% ammonia-methanol solution to the column. Let it stand for 2 min, then elute at a flow rate of 1-2 mL / min and collect the eluent.

[0082] (8) Concentrate the eluent to near dryness under a gentle nitrogen flow, add 100µL of initial mobile phase (5mM ammonium formate solution) to redissolve, then rinse the 0.2µm nylon microcentrifuge filter three times with methanol, transfer the concentrated extract to the filter, centrifuge at 6000rpm for 3min, transfer the filtered solution into a vial, add 10ng of internal standard, and wait for UPLC-MSMS detection. The method is as described in step (3) of Example 1 and Table 1.

[0083] The results are as follows Figure 1 and Figure 2 As shown, Method 1 is the method used in Example 1, and Method 2 is the method used in Comparative Example 1. It can be seen that regardless of the spiking amount of 1 ng ( Figure 1 ) or 10ng ( Figure 2 For all compounds, the spiked recoveries of Method 1 were significantly better than those of Method 2. The spiked recoveries of Method 1 were 60-120%, while those of Method 2 were basically unacceptable. In some cases, the spiked recoveries of octadecyltrimethylammonium chloride (C18-ATMAC) were even below 50%, indicating that Method 2 had poor resistance to matrix interference.

[0084] In summary, Method 1 in Embodiment 1 of this invention is significantly superior to Method 2 in Comparative Example 1.

[0085] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for detecting quaternary ammonium compounds in infant and toddler products, characterized in that, Includes the following steps: Step 1: Mix the sample of infant products with the recovery indicator and add it to a centrifuge tube, then perform the extraction operation and combine the extracts; Step 2: Concentrate the combined extracts, redissolve them in methanol, and then concentrate them again to obtain a concentrated extract. Centrifuge and collect the centrifuged extract. Step 3: Mix the centrifuged extract with the internal standard, and perform quantitative analysis of quaternary ammonium compounds using ultra-high performance liquid chromatography-tandem mass spectrometry.

2. The method for detecting quaternary ammonium compounds in infant products according to claim 1, characterized in that, The ratio of sample to recovery indicator was 0.2 g: 10 ng.

3. The method for detecting quaternary ammonium compounds in infant products according to claim 1, characterized in that, The recovery indicator was obtained by mixing benzyl dimethyl dodecyl ammonium-d7 chloride and benzyl dimethyl tetradecyl ammonium-d7 chloride in a 1:1 mass ratio; the internal standard was phosmet-d10.

4. The method for detecting quaternary ammonium compounds in infant products according to claim 1, characterized in that, The samples of the infant and toddler products include fiber samples and liquid samples.

5. The method for detecting quaternary ammonium compounds in infant products according to claim 4, characterized in that, The extraction process for the fiber-containing sample is as follows: Add the extraction solvent to the centrifuge tube, sonicate for 15 min, and centrifuge at 2500 rpm for 5 min. Repeat the extraction twice. Then add acetonitrile to the extracted fiber-containing sample, sonicate for 15 min, and centrifuge at 2500 rpm for 5 min. Repeat the extraction twice. Combine the four extracts.

6. The method for detecting quaternary ammonium compounds in infant products according to claim 4, characterized in that, The centrifugation conditions for the fiber-containing samples were as follows: the concentrated extract was transferred to a 0.2 μm nylon microcentrifuge filter rinsed with methanol and centrifuged at 6000 rpm for 3 min.

7. The method for detecting quaternary ammonium compounds in infant products according to claim 4, characterized in that, The extraction process for the liquid sample is as follows: Add the extraction solvent to the centrifuge tube, sonicate for 15 minutes, centrifuge at 2500 rpm for 5 minutes, repeat the extraction four times, and then combine the extracts.

8. The method for detecting quaternary ammonium compounds in infant products according to claim 4, characterized in that, The centrifugation conditions for the liquid sample were as follows: the concentrated extract was frozen at -80°C for 6 hours, and then centrifuged at -10°C and 13,000 rpm for 5 minutes.

9. A method for detecting quaternary ammonium compounds in infant products according to claim 5 or claim 7, characterized in that, The extractant is a mixture of n-hexane and dichloromethane in a volume ratio of 1:

1.

10. The application of the method for detecting quaternary ammonium compounds in infant products according to claim 1 in the detection of complex matrices.

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