QACs probe solution, probe and method for rapidly screening and accurately analyzing QACs

Abstract

The invention provides a novel method for rapidly screening and accurately analyzing the quaternary ammonium salt surfactant. In order to solve the problems of weak selectivity or long time consumption and high cost of a detection method in the prior art, a sodium tetraphenylborate-bromcresol purple-phosphate buffer salt mixed solution is adopted as a probe solution, quaternary ammonium salt surfactants in a sample are rapidly identified through probe reaction, a positive sample is subjected to high-speed centrifugation, dissolution and precipitation, and the content of the quaternary ammonium salt surfactants in the sample is detected. Further liquid chromatography-mass spectrometry analysis is carried out, so that accurate qualitative and quantitative analysis on the quaternary ammonium salt surfactant is realized. The method can effectively meet the requirements of rapid screening and accurate analysis, has important practical value and wide application prospect, and can remarkably improve the working efficiency and reduce the analysis cost especially in the fields of environmental protection, daily chemical management and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of surfactant product analysis and detection, and in particular to a quaternary ammonium salt surfactant probe solution, its preparation, and application. Furthermore, the present invention also relates to a rapid detection technology and a precise quantification technology for quaternary ammonium salt surfactants using the probe solution. Technical Background

[0002] Quaternary ammonium cationic surfactants (QACs), a class of industrial additives widely used in detergents, disinfectants, and softeners, have raised concerns about their environmental behavior. Some varieties, such as D1821 (dioctadecyldimethylammonium chloride), are difficult to degrade in the environment and exhibit significant ecotoxicity to the ecosystem and aquatic communities, necessitating strict restrictions on their use and dosage. While some industry regulations and standards regulate the use of QACs and provide testing methods, many products in circulation or regulatory scenarios lack applicable QAC testing methods.

[0003] The QACs detection methods currently reported in the literature mainly include two-phase titration, spectrophotometry, liquid chromatography, and liquid chromatography-mass spectrometry. Among them, the two-phase titration method is more suitable for the quality control of the product itself; the spectrophotometry method is only applicable to specific product types. Both methods lack qualitative capabilities and have limitations in the analysis of unknown samples. Although liquid chromatography and liquid chromatography-mass spectrometry are advanced analytical methods, they are difficult to apply to on-site rapid screening and testing, and the analysis cost is high in the case of large-scale screening. Therefore, the development of a detection method that has both rapid screening characteristics and accurate qualitative and quantitative functions has important application value in fields such as environmental monitoring and circulation product analysis. However, there is currently a lack of probe solutions that can rapidly screen QACs, resulting in the inability to perform accurate qualitative and quantitative analysis. Summary of the Invention

[0004] In response to the problems existing in the prior art, the first object of the present invention is to provide a probe solution for rapidly indicating or screening quaternary ammonium surfactants (QACs). The probe solution is a mixed solution of sodium tetraphenylborate-bromocresol purple-phosphate buffer, wherein the total molar concentration of sodium tetraphenylborate and bromocresol purple is 2 mmol / L to 20 mmol / L, and the molar ratio of sodium tetraphenylborate to bromocresol purple is 100:1 to 500:1; the phosphate buffer solution is composed of sodium dihydrogen phosphate-disodium hydrogen phosphate and has a pH of 7 to 8; when the probe solution encounters a sample containing a quaternary ammonium surfactant, if the sample exhibits at least one of turbidity, precipitation, or discoloration due to the presence of the QACs, the sample can be determined to contain the quaternary ammonium surfactant.

[0005] The method for preparing a probe solution for rapid indication or screening of QACs of the present invention is as follows: (1) Prepare Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 2 mmol / L to 20 mmol / L. (2) Prepare Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 0.2 mmol / L to 2 mmol / L. (3) Prepare Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve them in water, and prepare a mixed buffer solution with a pH of 7-8 and a total concentration of 10 mmol / L-100 mmol / L. (4) Take an appropriate amount of liquid A and an appropriate amount of liquid B and mix them. The molar ratio of sodium tetraphenylborate to bromocresol purple in the mixed solution should be controlled at 100:1~500:1. Then add an appropriate amount of liquid C dropwise so that the pH value of the final solution is maintained at 7~8, thereby obtaining the probe solution.

[0006] A second object of the present invention is to provide a method for rapidly screening quaternary ammonium surfactants, comprising: taking a sample to be tested, dissolving it if necessary, and adding it dropwise to the probe solution of the present invention to obtain a sample solution; if the sample solution becomes turbid, precipitated, or discolored, the sample contains the quaternary ammonium surfactant; if the sample solution has no obvious change in appearance, the sample does not contain the quaternary ammonium surfactant.

[0007] As a preferred technical solution, based on the principle of the above-mentioned method for rapid screening of quaternary ammonium surfactants, the probe solution of the present invention can also be prepared into a droplet probe for rapid indication or screening of quaternary ammonium surfactants, which is more convenient to use.

[0008] A third object of the present invention is to provide a method for rapidly screening and accurately analyzing quaternary ammonium surfactants using the above-mentioned probe solution, comprising the following steps: (1) Rapid screening: Take the sample to be tested, dissolve it if necessary, and add it dropwise to the probe solution of the present invention to obtain a sample solution. If the sample solution becomes turbid, precipitates, or fades, it is determined to be positive, indicating that the sample contains a quaternary ammonium surfactant. If the sample solution has no obvious change in appearance, it is determined to be negative, indicating that the sample does not contain a quaternary ammonium surfactant. (2) Accurate analysis: a. Take the sample solution that is quickly screened as positive in step (1), and centrifuge it at high speed. The supernatant should remain purple. If it fades significantly, reduce the sample volume and repeat step (1) until the positive sample solution is centrifuged at high speed and the supernatant remains purple. b. After the sample solution is centrifuged, discard the supernatant, add an appropriate amount of solvent to dissolve the precipitate, and then send it to liquid chromatography-mass spectrometry for accurate qualitative and quantitative analysis.

[0009] Preferably, in step (1), the sample sampling amount is 1 g to 5 g, and if necessary, 1 mL to 5 mL of solvent is added to dissolve to obtain a transparent solution; the solvent is selected from one or more of water, methanol, ethanol, and isopropanol.

[0010] Preferably, the solvent for dissolving the precipitate in step (2) is one of benzene, ketone, alcohol, or chlorinated alkane solvents, or their corresponding aqueous solutions, or a liquid chromatography mobile phase. More preferably, the solvent is one of benzene, toluene, acetone, isopropanol, or carbon tetrachloride, or their corresponding aqueous solutions; and the liquid chromatography mobile phase is an ammonium acetate aqueous solution-acetonitrile-water system.

[0011] Preferably, in step (2), the analysis conditions of the liquid chromatography-mass spectrometry are as follows: the chromatographic column adopts a ThermoAcclaim Surfactant Plus column; the mobile phase is an ammonium acetate aqueous solution-acetonitrile-water system, and a gradient elution mode is adopted; the mass spectrometer is equipped with an electrospray ion source, and selectively monitors or extracts characteristic target ions in positive ion mode. More preferably, the concentration of the ammonium acetate aqueous solution in the mobile phase combination is 50 mmol / L to 100 mmol / L, and the pH value is 4.5~5.5; the gradient program used is set as follows: the ammonium acetate aqueous solution is used as the mobile phase A, acetonitrile is used as the mobile phase B, and water is used as the mobile phase C. The volume ratio of the mobile phase A is maintained at a fixed value of 5%~10% throughout the gradient program; elution separation is achieved by adjusting the ratio of the mobile phase B to the mobile phase C, and the volume ratio of the mobile phase B is maintained at 50% to 60% within an initial time period of 1 min~2 min. Subsequently, within a time period of 2 min~10 min, the volume ratio gradient of the mobile phase B is increased to 80%~90%, and the volume ratio gradient of the mobile phase C is simultaneously reduced to 15%~0% to achieve complete elution of the target component.

[0012] The innovative features of the technical solution of the present invention are:

[0013] (1) Innovation of probe solution: Sodium tetraphenylborate, bromocresol purple, and phosphate buffer are combined in a specific ratio to form a synergistic effect under specific conditions, resulting in new properties. This makes the probe solution highly sensitive and easy to observe. This property cannot be exhibited when the reagents are used alone and has not been reported.

[0014] (2) Innovation in the integration of probe identification and enrichment and separation: The quaternary ammonium surfactant is precipitated and enriched while being identified, and is separated from most impurities after high-speed centrifugation. The analytical method realizes the integration of identification, enrichment and separation.

[0015] (3) Innovation in method design: This scheme combines the probe solution method and the instrumental analysis method, so that the scheme as a whole has both the ability to quickly identify and the ability to further accurately determine the quality and quantify. Compared with existing methods, the method of the present invention combines the high efficiency of the rapid indication method and the accuracy of the instrumental analysis method, and can provide the detection results of QACs in a short time, at a low cost, and with significant advancement.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) Rapid screening, cost reduction and efficiency improvement: Through the rapid reaction mechanism of the specially formulated probe solution, the presence of quaternary ammonium surfactants in the sample can be quickly detected, significantly shortening the initial screening time and being suitable for on-site rapid identification. At the same time, a large number of negative samples can be effectively excluded, significantly improving work efficiency and reducing analysis costs.

[0018] (2) The method is simple, sensitive and accurate: After a simple separation operation, the quaternary ammonium surfactant is effectively enriched, providing high-quality test samples for subsequent liquid chromatography-mass spectrometry analysis, making the overall solution simpler, more sensitive and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the extracted ion chromatogram of the liquid chromatography-mass spectrometry analysis for determining the D1821 component in the softener product in Example 1. DETAILED DESCRIPTION

[0020] Quaternary ammonium salt cationic surfactants (‌QACs) are a type of cationic surfactant formed by replacing all four hydrogen atoms of the ammonium cation [H4N+] with organic groups. They mainly include alkyltrimethylammonium salt type cationic surfactants, dialkyldimethylammonium salt type cationic surfactants, alkyldimethylbenzylammonium type cationic surfactants, pyridinium salt type cationic surfactants, alkylisoquinolinium salt type cationic surfactants and benzylammonium chloride type cationic surfactants.

[0021] The inventors accidentally discovered that a specific combination of sodium tetraphenylborate, bromocresol purple, and phosphate buffered saline in a specific ratio produces a novel property under specific conditions. This mixture exhibits at least one of turbidity, precipitation, or discoloration when exposed to a sample containing a quaternary ammonium surfactant. This allows it to be used as a highly sensitive and easily observable indicator for rapid screening of quaternary ammonium surfactants (QACs). The basic principle is as follows:

[0022]

[0023] Wherein: NaB(C6H5)4 represents sodium tetraphenylborate, R represents bromocresol purple, Q+ represents quaternary ammonium salt cationic surfactant, and PBS represents phosphate buffered saline.

[0024] The reaction of sodium tetraphenylborate with QACs is the fundamental principle of the commonly used two-phase titration method. However, the inventors discovered that under specific conditions, sodium tetraphenylborate and bromocresol purple can produce a synergistic effect, reacting with QACs to form a complex precipitate. This precipitation is sensitive, rapid, and complete, and can be separated by simple centrifugation, achieving the goal of enriching and isolating the QACs. Furthermore, once the sodium tetraphenylborate is consumed, the QACs will independently combine with bromocresol purple to form a complex, causing the bromocresol purple solution to fade. Therefore, fading can indicate that the concentration of QACs in the sample solution is too high, requiring a reduced sample volume to prevent incomplete enrichment.

[0025] QACs are identified through the above operations and then enriched and separated from most impurities, providing high-quality samples for further liquid chromatography-mass spectrometry analysis. Under the optimized chromatographic conditions, QACs peaks are undisturbed and highly sensitive.

[0026] The technical solutions provided by the present invention are described in detail below with reference to the examples. It should be noted that the following examples are only some preferred implementation methods of the present invention. All examples obtained by combination, simple transformation, parameter range modification, etc. under the guidance of the spirit of the present invention fall within the scope of protection of the present invention.

[0027] Example 1: Screening and detection of D1821 in a commercially available softener product

[0028] (I) Preparation of probe solution: Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 15 mmol / L; Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 0.2 mmol / L; Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve in water, and prepare a mixed buffer solution with a pH of 7 and a total concentration of 100 mmol / L. Mix 5 mL of Solution A and Solution B, and place them in a 15 mL transparent centrifuge tube. After mixing, the molar ratio of sodium tetraphenylborate to bromocresol purple in the solution is 100:1. Add 5 mL of Solution C, and the final pH value of the solution is 7 to obtain the probe solution.

[0029] (2) Measurement process: Dissolve 5g of a commercially available sample in water to a clear solution, then transfer to a 5mL volumetric flask. Add 1mL of the sample solution dropwise to the probe solution prepared above. A purple precipitate immediately forms in the probe solution, indicating a positive sample. Centrifuge at 4000 rpm; the supernatant is significantly less discolored than the probe solution.

[0030] A further 2 g sample was taken and the above steps were repeated. After centrifugation, the supernatant remained purple and showed no signs of fading. The supernatant was discarded, and the precipitate was dissolved in a 50% acetone-water solution, diluted to 10 mL, and sent to a liquid chromatography-mass spectrometer for further analysis.

[0031] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 150 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ionization source and monitored in positive ion mode; characteristic target ions such as dihexadecyldimethylammonium chloride (m / z 494.6), hexadecyloctadecyldimethylammonium chloride (m / z 522.6), and dioctadecyldimethylammonium chloride (m / z 550.7) were extracted.

[0032] Elution program: Mobile phase A is 100 mmol / L ammonium acetate aqueous solution (adjusted to pH 5.0 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0033] Table 1 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 5 55 40 2 5 55 40 8 5 85 10 10 5 55 40 Under the above conditions, the extracted ion chromatogram of D1821 standard working solution is shown in the attached figure. Figure 1 .

[0034] It was determined that the content of D1821 in the softener product was 6%.

[0035] Example 2: Screening of D1821 surfactant in a commercially available laundry detergent

[0036] (I) Preparation of probe solution: Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 20 mmol / L; Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 2 mmol / L; Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve in water, and prepare a mixed buffer solution with a pH of 7.5 and a total concentration of 20 mmol / L. Mix solution A and solution B, totaling 6 mL, and place in a 20 mL transparent centrifuge tube. After mixing, the molar ratio of sodium tetraphenylborate: bromocresol purple in the solution is 500:1; add 6 mL of solution C, and the final pH value of the solution is 7.5 to obtain the probe solution.

[0037] (2) Measurement process: Dissolve 2 g of the commercially available sample in isopropyl alcohol to a clear solution. Transfer the solution to a 5 mL volumetric flask and bring to volume. Add 1 mL of the sample solution dropwise to the probe solution prepared above. If the probe solution shows no significant reaction, the sample is considered negative and does not contain the D1821 surfactant.

[0038] Example 3: Missed Detection Troubleshooting Another 2 g of the sample from Example 2 was taken, dissolved in isopropanol to form a transparent solution, transferred to a 5 mL volumetric flask, fixed to volume, and sent to a liquid chromatography-mass spectrometer for missed detection and troubleshooting.

[0039] The same liquid chromatography-mass spectrometry detection conditions as in Example 1 were used for detection. The results showed that no characteristic molecular weight information of D1821 was found, which proved that the rapid screening method of this scheme had a low missed detection rate and accurate determination results.

[0040] Example 4: Screening and Detection of Quaternary Ammonium Surfactants in a Commercially Available Disinfectant Product

[0041] (I) Preparation of probe solution: Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 5 mmol / L; Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 2 mmol / L; Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve in water, and prepare a mixed buffer solution with a pH of 8 and a total concentration of 10 mmol / L. Take liquid A and liquid B and mix them, totaling 10 mL, and place them in a 25 mL transparent centrifuge tube. After mixing, the molar ratio of sodium tetraphenylborate: bromocresol purple in the solution is 200:1; add 10 mL of liquid C, and the final pH value of the solution is 8 to obtain the probe solution.

[0042] (2) Measurement process: Dissolve 3g of a commercially available sample in water to a clear solution, then transfer to a 5mL volumetric flask and adjust to volume. Pipette 1mL of the sample solution and dropwise add it to the probe solution prepared above. A purple precipitate immediately appears in the probe solution, indicating a positive sample. Centrifuge at 3000 rpm; the supernatant shows no significant discoloration compared to the probe solution.

[0043] The supernatant was discarded, the precipitate was dissolved with acetone, the mobile phase was diluted to 5 mL, and sent to liquid chromatography-mass spectrometry for further analysis.

[0044] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 250 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ion source and monitored in positive ion mode; characteristic target ions were extracted, such as dodecyltrimethylammonium chloride (m / z 228.3), dodecyldimethylbenzylammonium chloride (m / z 304.3), dihexadecyldimethylammonium chloride (m / z 494.6), hexadecyldimethylammonium chloride (m / z 522.6), and dioctadecyldimethylammonium chloride (m / z 550.7).

[0045] Elution program: Mobile phase A is 50 mmol / L ammonium acetate aqueous solution (adjusted to pH 4.5 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0046] Table 2 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 10 50 40 1 10 50 40 10 10 80 10 After analysis, the product contained dodecyltrimethylammonium chloride and dodecyldimethylbenzylammonium chloride. Determined by external standard method, the content of dodecyltrimethylammonium chloride was 0.52% and the content of dodecyldimethylbenzylammonium chloride was 0.15%.

[0047] The sample preparation was repeated 6 times, and the results were as follows:

[0048] Table 3 Precision investigation Serial number Dodecyltrimethylammonium chloride Dodecyldimethylbenzyl ammonium chloride 1 0.52% 0.14% 2 0.54% 0.15% 3 0.54% 0.13% 4 0.50% 0.15% 5 0.56% 0.14% 6 0.51% 0.14% RSD / % 4.2 5.3 The relative standard deviation (RSD) value was less than 6%, indicating that the determination method had good precision.

[0049] Example 5: Screening and detection of quaternary ammonium surfactants in wastewater from a factory

[0050] Prepare the probe solution in advance using the same method as in Example 4.

[0051] Measurement process: Wastewater from a factory outlet was added dropwise to the probe solution prepared above. A purple precipitate immediately formed in the probe solution, indicating a positive sample. Centrifugation at 5000 rpm revealed no significant discoloration of the supernatant compared to the probe solution. The supernatant was discarded, the precipitate dissolved in acetone, and the mobile phase diluted to 5 mL before analysis by liquid chromatography-mass spectrometry.

[0052] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 100 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ion source and monitored in positive ion mode. The SCAN mode was used to scan in the molecular weight range of 100 to 1000.

[0053] Elution program: Mobile phase A is 80 mmol / L ammonium acetate aqueous solution (adjusted to pH 5.5 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0054] Table 4 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 5 60 35 2 5 60 35 10 5 90 5 After analysis, the wastewater was found to contain didecyldimethylammonium chloride, and its content was determined to be 0.1% by external standard method.

[0055] Example 6: Identification and Detection of Quaternary Ammonium Surfactants in a Commercially Available Disinfectant Product

[0056] (I) Preparation of probe solution: Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 15 mmol / L; Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 0.4 mmol / L; Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve in water, and prepare a mixed buffer solution with a pH of 7 and a total concentration of 100 mmol / L. Mix 5 mL of Solution A and Solution B, and place them in a 15 mL transparent centrifuge tube. After mixing, the molar ratio of sodium tetraphenylborate to bromocresol purple in the solution is 100:1. Add 5 mL of Solution C, and the final pH value of the solution is 7 to obtain the probe solution.

[0057] (2) Measurement process: Take 5g of a commercially available disinfectant sample, add water to dissolve it into a clear solution, and transfer it to a 5mL volumetric flask to the volume. Pipette 1mL of the sample solution and drop it into the probe solution prepared as above. The probe solution immediately develops a purple precipitate, which is determined to be a positive sample. Centrifuge at 4000r / min. The supernatant does not show any significant discoloration compared to the probe solution. Discard the supernatant, dissolve the precipitate in a 50% acetone-water solution, dilute to 10mL, and send it to a liquid chromatography-mass spectrometer for further accurate identification and analysis.

[0058] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 150 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ionization source and monitored in positive ion mode. Characteristic target ions extracted included dihexadecyldimethylammonium chloride (m / z 494.6), hexadecetyldimethylammonium chloride (m / z 522.6), dioctadecyldimethylammonium chloride (m / z 550.7), hexadecyltrimethylammonium bromide (284.3), dodecyltrimethylammonium chloride (228.3), octadecyltrimethylammonium chloride (312.4), benzalkonium chloride (304.3), and hexadecylpyridinium chloride (340.0).

[0059] Elution program: Mobile phase A is 100 mmol / L ammonium acetate aqueous solution (adjusted to pH 5.0 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0060] Table 5 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 5 55 40 2 5 55 40 8 5 85 10 10 5 55 40 Under the above conditions, it is accurately identified that the disinfectant contains: hexadecyltrimethylammonium bromide and benzalkonium chloride.

[0061] It has been determined that the contents of cetyltrimethylammonium bromide and benzalkonium chloride in this disinfectant product are 0.5% and 0.3% respectively.

[0062] Example 7: Identification and Detection of Quaternary Ammonium Surfactants in a Commercially Available Pet Shampoo Product

[0063] (I) Preparation of probe solution: Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 10 mmol / L; Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 0.8 mmol / L; Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve in water, and prepare a mixed buffer solution with a pH of 7 and a total concentration of 80 mmol / L. Mix 5 mL of Solution A and Solution B, and place them in a 15 mL transparent centrifuge tube. After mixing, the molar ratio of sodium tetraphenylborate to bromocresol purple in the solution is 150:1. Add 5 mL of Solution C, and the final pH value of the solution is 7 to obtain the probe solution.

[0064] (2) Measurement process: Take 5g of commercially available sample, add water to dissolve it into a transparent solution, transfer it to a 5mL volumetric flask and make up the volume. Pipette 1mL of sample solution and drop it into the probe solution prepared as above. The probe solution immediately shows a purple precipitate, which is determined to be a positive sample. Centrifuge at 4000r / min. The supernatant does not show obvious fading compared with the probe solution. The supernatant is discarded, and the precipitate is dissolved with 80% acetone-water solution and made up to 10mL with the initial mobile phase. It is sent to liquid chromatography-mass spectrometry for further accurate identification and analysis.

[0065] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 150 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ion source and monitored in positive ion mode. The SCAN mode was used to scan in the molecular weight range of 100 to 1000.

[0066] Elution program: Mobile phase A is 100 mmol / L ammonium acetate aqueous solution (adjusted to pH 5.0 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0067] Table 6 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 5 60 35 2 5 60 35 10 5 90 5 Under the above conditions, it is accurately identified that the product contains: octadecyldimethylammonium chloride.

[0068] It was determined that the content of octadecyl dimethyl ammonium chloride in the product was 0.8%.

[0069] Example 8: Detection of quaternary ammonium surfactant residues in a degradation tank of a sewage treatment plant

[0070] Prepare the probe solution in advance using the same method as in Example 6.

[0071] Measurement process: Take 200 mL of sample from the sampling port of the degradation tank, shake well, draw 1 mL, and drop it into the probe solution prepared as above. If there is no obvious reaction in the probe solution, it is judged as a negative sample.

[0072] Another 5 mL of sample was taken, diluted to 5 mL with the initial mobile phase, and sent to the liquid chromatography-mass spectrometry instrument for missed detection confirmation.

[0073] The analysis conditions of liquid chromatography-mass spectrometry are as follows: The chromatographic column used was a Thermo Acclaim Surfactant Plus column (4.6 mm × 100 mm, 3 μm); The mobile phase was an ammonium acetate aqueous solution-acetonitrile-water system in a gradient elution mode with a flow rate of 1.0 mL / min; The mass spectrometer was equipped with an electrospray ion source and monitored in positive ion mode. The SCAN mode was used to scan in the molecular weight range of 100 to 1000.

[0074] Elution program: Mobile phase A is 100 mmol / L ammonium acetate aqueous solution (adjusted to pH 5.0 with acetic acid), mobile phase B is acetonitrile, and mobile phase C is water. The gradient elution program is shown in the table below:

[0075] Table 7 Gradient elution program Time min Mobile phase A Mobile phase B Mobile phase C 0 5 60 35 2 5 60 35 10 5 90 5 As a result, no characteristic ion peaks of common quaternary ammonium surfactants were detected in the molecular weight range of 100 to 1000, proving that the conclusion that the probe solution was negative was accurate.

[0076] Comparative Example 1:

[0077] Take 5 g of the sample from Example 1, add water to dissolve it into a transparent solution, and transfer it to a 5 mL volumetric flask to make up the volume.

[0078] 1 mL of the sample solution was pipetted and added dropwise to a 15 mmol / L sodium tetraphenylborate solution. The probe solution became turbid but with no apparent precipitation. After centrifugation at 4000 rpm, the supernatant became transparent and the precipitate was white. The supernatant was discarded and analyzed by liquid chromatography-mass spectrometry as in Example 1. The content of D1821 in the product was 2%, significantly lower than the actual content of 6%.

[0079] This comparative example shows that when only sodium tetraphenylborate is used as the probe solution, the precipitation reaction is relatively slow, the precipitate is white in color, and is difficult to observe. In addition, it is impossible to determine whether the precipitation is complete, and the measurement result is low.

[0080] Comparative Example 2:

[0081] Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 2mmol / L. Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve them in water to prepare a mixed buffer solution with a pH of 8 and a total concentration of 10mmol / L. Take 10 mL of solution B, place it in a 25 mL transparent centrifuge tube, add 10 mL of solution C, and the final pH value of the solution is 8, which is used as the probe solution.

[0082] Get embodiment 4 sample 3g, be dissolved in water as clear solution, be transferred to constant volume in 5mL volumetric flask.Pipette sample solution 1mL, splash in the probe solution of preparation as above, there is fading phenomenon in probe solution, but has no obvious precipitation.This solution, as testing solution, is sent to liquid chromatography-mass spectrometry and is analyzed, and adopts analytical condition and operation identical with embodiment 4, and result fails to detect quaternary ammonium salt surfactant.

[0083] This comparative example shows that using only bromocresol purple-phosphate buffer as the probe solution, although it can indicate the presence of quaternary ammonium surfactants, cannot achieve separation and enrichment through precipitation reaction, resulting in the concentration of the analyte in the sample solution being lower than the instrument detection limit, and accurate results cannot be obtained for further analysis.

[0084] Comparative Example 3:

[0085] The commercially available water treatment agent raw material, dodecyldimethylbenzyl ammonium chloride (1227), was analyzed using QB / T 1915-2021 and this protocol. The results are compared as follows:

[0086] Table 8 Result analysis comparison table Serial number Analytical results using QB / T 1915-2021 Analyze the results using this solution 1 30.1% 30.4% 2 30.3% 30.5% 3 30.2% 30.3% mean 30.2% 30.4% This comparative example shows that the results of this solution are close to those of the standard method.

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A probe solution for rapid indication or screening of quaternary ammonium surfactants, characterized in that: The probe solution is a mixed solution of sodium tetraphenylborate-bromocresol purple-phosphate buffer saline, wherein the total molar concentration of sodium tetraphenylborate and bromocresol purple is 2 mmol / L to 20 mmol / L and the molar ratio of sodium tetraphenylborate to bromocresol purple is 100:1 to 500:1; the phosphate buffer saline solution is composed of sodium dihydrogen phosphate and disodium hydrogen phosphate and has a pH value of 7 to 8; and when the probe solution encounters a sample containing a quaternary ammonium surfactant, if at least one of turbidity, precipitation, or fading occurs, it is determined that the sample contains a quaternary ammonium surfactant.

2. A method for preparing a probe solution for rapid indication or screening of quaternary ammonium surfactants, comprising the following steps: (1) Prepare Solution A: Weigh sodium tetraphenylborate and dissolve it in water to prepare a solution with a concentration of 2 mmol / L to 20 mmol / L. (2) Prepare Solution B: Weigh bromocresol purple, dissolve it in a small amount of ethanol, and dilute it with water to prepare a solution with a concentration of 0.2 mmol / L to 2 mmol / L. (3) Prepare Solution C: Weigh sodium dihydrogen phosphate and disodium hydrogen phosphate, dissolve them in water, and prepare a mixed buffer solution with a pH of 7-8 and a total concentration of 10 mmol / L-100 mmol / L. (4) Take an appropriate amount of liquid A and an appropriate amount of liquid B and mix them. The molar ratio of sodium tetraphenylborate to bromocresol purple in the mixed solution should be controlled at 100:1~500:

1. Then add an appropriate amount of liquid C dropwise so that the pH value of the final solution is maintained at 7~8, thereby obtaining the probe solution.

3. A method for rapid screening of quaternary ammonium surfactants, characterized in that: Taking a sample to be tested, dissolving it if necessary, and adding it dropwise to the probe solution according to claim 1 to obtain a sample solution. If the sample solution shows at least one of turbidity, precipitation, or fading, the sample contains a quaternary ammonium surfactant; If there is no obvious change in the appearance of the sample solution, the sample does not contain quaternary ammonium surfactants.

4. A droplet probe for rapid indication or screening of quaternary ammonium surfactants prepared using the probe solution according to claim 1.

5. A method for rapid screening and accurate analysis of quaternary ammonium surfactants, characterized in that: The following steps are involved: (1) Rapid screening: Take the sample to be tested, dissolve it if necessary, and add it dropwise to the probe solution described in claim 1 to obtain a sample solution. If the sample solution becomes turbid, precipitates, or fades, it is determined to be positive, indicating that the sample contains a quaternary ammonium surfactant. If the sample solution has no obvious change in appearance, it is determined to be negative, indicating that the sample does not contain a quaternary ammonium surfactant. (2) Accurate analysis: a. Take the sample solution that is quickly screened as positive in step (1), and centrifuge it at high speed. The supernatant should remain purple. If it fades significantly, reduce the sample volume and repeat step (1) until the positive sample solution is centrifuged at high speed and the supernatant remains purple. b. After the sample solution is centrifuged, discard the supernatant, add an appropriate amount of solvent to dissolve the precipitate, and then send it to liquid chromatography-mass spectrometry for accurate qualitative and quantitative analysis.

6. The method according to claim 5, characterized in that In the step (1), the sample sampling amount is 1 g to 5 g, and if necessary, 1 mL to 5 mL of solvent is added to dissolve the sample to obtain a transparent solution; the solvent is selected from one or more of water, methanol, ethanol, and isopropanol.

7. The method according to claim 5, characterized in that The solvent for dissolving the precipitate in step (2) is one of benzene, ketone, alcohol or chlorinated alkane solvents or their corresponding aqueous solutions, or a liquid chromatography mobile phase.

8. The method according to claim 7, characterized in that The solvent is one of benzene, toluene, acetone, isopropyl alcohol or carbon tetrachloride or their corresponding aqueous solutions; the liquid chromatography mobile phase is an ammonium acetate aqueous solution-acetonitrile-water system.

9. The method according to claim 5, characterized in that The analysis conditions of the liquid chromatography-mass spectrometry in step (2) are as follows: the chromatographic column is a Thermo Acclaim Surfactant Plus column; the mobile phase is an ammonium acetate aqueous solution-acetonitrile-water system, and the gradient elution mode is adopted; the mass spectrometer is equipped with an electrospray ion source, and the characteristic target ions are selectively monitored or extracted in the positive ion mode.

10. The analysis method according to claim 9, characterized in that: The concentration of the ammonium acetate aqueous solution in the mobile phase combination is 50 mmol / L to 100 mmol / L, and the pH value is 4.5 to 5.5; The gradient program of the gradient elution mode is set as follows: ammonium acetate aqueous solution is used as mobile phase A, acetonitrile is used as mobile phase B, and water is used as mobile phase C. The volume ratio of mobile phase A is maintained at a fixed value of 5% to 10% throughout the gradient program; elution separation is achieved by adjusting the ratio of mobile phase B to mobile phase C, and the volume ratio of mobile phase B is maintained at 50% to 60% within an initial time period of 1 min to 2 min. Subsequently, within a time period of 2 min to 10 min, the volume ratio gradient of mobile phase B is increased to 80% to 90%, and the volume ratio gradient of mobile phase C is simultaneously reduced to 15% to 0% to achieve complete elution of the target component.

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