A method for high-efficiency detection of 40 kinds of quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry

Abstract

The present application relates to the technical fields of environmental detection and pollutant analysis, and particularly relates to a high-efficiency detection method for 40 kinds of quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry. The present application uses a WCX solid-phase extraction column to complete enrichment and purification of a sample, realizes separation of target objects through a C18 reversed-phase chromatographic column combined with an optimized methanol-water mobile phase gradient elution program, adopts a multiple reaction monitoring technology in a positive ion mode of an electrospray ion source, and optimizes exclusive parent ion-daughter ion pairs, collision energy and de-clustering potential parameters for the 40 kinds of quaternary ammonium salt compounds. The present method has a detection limit of 0.1-0.5 mu g / L, a quantitative limit of 0.01-200 mu g / L, a correlation coefficient R 2 >=0.995, all target objects complete baseline separation within 20 minutes, has the advantages of high throughput, high sensitivity and simple operation, and is suitable for synchronous quantitative detection of quaternary ammonium salt pollutants in complex environmental samples.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring and pollutant analysis technology, and in particular to a highly efficient method for the detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry. Background Technology

[0002] Quaternary ammonium compounds (QACs) are important industrial additives widely used in plastics, textiles, and synthetic materials, often serving as antibacterial agents, surfactants, preservatives, antistatic agents, softeners, and dispersants. Furthermore, due to their ability to disrupt bacterial cell membranes, QACs are commonly found in cleaning products, hand sanitizers, personal care products, various wipes (surface wipes, baby wipes, hand wipes, and disinfectant wipes), and various insecticides. During the COVID-19 pandemic, of the 430 disinfectant products listed by the EPA for COVID-19 eradication, 216 used QACs as active ingredients.

[0003] Disinfectants containing quaternary ammonium compounds (QACs) flow into sewers with domestic sewage and eventually reach wastewater treatment plants (WWTPs). Therefore, WWTPs are a critical point where QACs enter the natural environment. Studies have shown that high concentrations of QACs are frequently detected in WWTP influent, with particularly high levels of BACs (such as BAC C12 and C14) and DADMACs (such as DADMAC C10), reaching concentrations as high as 170 μg / L. Quaternary ammonium compounds not only pollute water and soil but can also cause ecosystem imbalances through bioaccumulation, posing a potential threat to human health.

[0004] Currently, the detection of quaternary ammonium compounds mainly relies on high-performance liquid chromatography-mass spectrometry (LC-MS) or direct mass spectrometry. However, existing technologies generally suffer from problems such as cumbersome sample pretreatment, insufficient sensitivity, severe signal interference, and limited detection range, which are not conducive to the accurate monitoring of trace QACs in the environment. Summary of the Invention

[0005] The purpose of this invention is to provide a highly efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry (LC-MS). By combining ultra-high resolution mass spectrometry analysis with optimized ion source conditions, the detection method provided by this invention achieves rapid, sensitive, and accurate detection of 40 typical quaternary ammonium salt compounds in complex environmental samples. It has advantages such as low detection limit, high resolution, and simple method, providing strong technical support for the tracking and assessment of environmental pollutants.

[0006] To achieve the above objectives, this invention provides a high-efficiency detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry, comprising the following steps: S1. Add 50 μL of dodecyl dimethyl ammonium chloride-d25 internal standard solution, 50 μL of tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution, and 50 μL of hexadecyl trimethyl ammonium chloride-d9 internal standard solution to 100 mL of pretreated water sample to obtain the water sample standard solution. Perform solid phase extraction, elution, and concentration on the water sample standard solution to obtain the test solution. S2. Plot a standard curve, then inject the test solution and blank solution into a high performance liquid chromatography-tandem mass spectrometry system for analysis. Adjust the chromatographic and mass spectrometry conditions to obtain the contents of 40 quaternary ammonium salt compounds. The quaternary ammonium salt compound is a tetravalent nitrogen cationic compound; The chromatographic conditions used were as follows: a C18 reversed-phase column; gradient elution program; mobile phase A was an aqueous solution composed of ammonium acetate, formic acid, and water; the concentration of ammonium acetate in the aqueous solution was 5 mmol / L, and the volume fraction of formic acid was 0.1%; mobile phase B was a methanolic solution of formic acid with a volume fraction of 0.1%; the flow rate was 0.4-0.5 mL / min; and the column temperature was 40-50℃. The mass spectrometry conditions were as follows: positive ion mode of electrospray ionization source, multiple reaction monitoring (MRM); nebulizer gas temperature 450℃; nebulizer gas pressure 50psi; auxiliary gas pressure 50psi; nozzle voltage 5000V; collision gas pressure 8psi; curtain gas pressure 20psi; segmented acquisition mode, isolation time window 0.5min.

[0007] In this invention, the tetravalent nitrogen cationic compounds include diallyl dimethyl ammonium chloride (DDA), 1-butyl-1-methylpyrrolidone onium chloride (BMPC), (3-carboxypropyl)trimethylammonium chloride (CPAC), benzyltrimethylammonium bromide (BTMAC), 1-butyl-3-methylimidazolium chloride (BMLC), (5-bromopentyl)trimethylammonium bromide (BPTMAC), benzyltributylammonium chloride (BTBAC), benzyltriethylammonium bromide (BTEAC), S-butyrylthiocholine iodide (SBTCC), tetrapropylammonium bromide (TPABC), and 1-hexyl-3-methylammonium chloride (TBMC). 1,2-Dimethyl-3,5-diphenylpyrazolium chloride (HMIMCl), dodecylethyl dimethylammonium bromide (TMABC), 1,2-dimethyl-3,5-diphenylpyrazolium methyl sulfate (DB), hexyl dimethyl benzyl ammonium chloride (C6-BAC), octyl trimethyl ammonium chloride (C8-ATMAC), octyl dimethyl benzyl ammonium chloride (C8-BAC), decyl trimethyl ammonium bromide (C10-ATMAC), decyl dimethyl benzyl ammonium chloride (C10-BAC), dodecyl trimethyl ammonium chloride (C12-ATMAC), and didodecyl dimethyl ammonium bromide (C2-12-DADMAC). Dioctyl dimethyl ammonium bromide (C8-DADMAC), dodecyl dimethyl benzyl ammonium chloride (C12-BAC), tetradecyl trimethyl ammonium chloride (C14-ATMAC), dodecyl dimethyl (2-phenoxyethyl) ammonium bromide (DMPC), decyl dimethyl octyl ammonium chloride (C8-10-DADMAC), tetradecyl dimethyl benzyl ammonium chloride (C14-BAC), hexadecyl trimethyl ammonium chloride (C16-ATMAC), didecyl dimethyl ammonium chloride (C10-DADMAC), hexadecylpyridinium bromide (CPB), methyl trioctyl ammonium chloride (MTOAC) Tetraheptylammonium bromide (THAC), benzyl dimethyl hexadecyl ammonium chloride (C16-BAC), octadecyl trimethylammonium chloride (C18-ATMAC), octadecyl dimethyl benzyl ammonium chloride (C18-BAC), dimethyl ditetradecyl ammonium bromide (C12-DADMAC), dimethyl dioctadecyl ammonium bromide (C14-DADMAC), dihexadecyl dimethyl ammonium bromide (C16-DADMAC), dioctadecyl dimethyl ammonium chloride (C18-DADMAC), 1-decyl-3-methylimidazolium chloride (C10MIN), and benzyl ammonium chloride (BEC).

[0008] In this invention, the pretreatment process of the water sample to be tested includes: filtering the water sample to be tested through a glass fiber filter membrane with a pore size of 0.45 μm to obtain a pretreated water sample to be tested.

[0009] In this invention, the concentration of the dodecyl dimethyl ammonium chloride-d25 internal standard solution is 1 mg / L; the concentration of the tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution is 1 mg / L; and the concentration of the hexadecyl trimethyl ammonium chloride-d9 internal standard solution is 1 mg / L.

[0010] In this invention, the preparation process of the bis(dodecyl)dimethylammonium chloride-d25 internal standard solution includes: dissolving the bis(dodecyl)dimethylammonium chloride-d25 standard in methanol and making up to volume to obtain a single standard stock solution; diluting the single standard stock solution with methanol to obtain a 1 mg / L bis(dodecyl)dimethylammonium chloride-d25 internal standard solution.

[0011] In this invention, the preparation process of the tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution includes: dissolving the tetradecyl dimethyl benzyl ammonium chloride-d7 standard in methanol and making up to volume to obtain a single standard stock solution; diluting the single standard stock solution with methanol to obtain a 1 mg / L tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution.

[0012] In this invention, the preparation process of the hexadecyltrimethylammonium chloride-d9 internal standard solution includes: dissolving the hexadecyltrimethylammonium chloride-d9 standard in methanol and making up to volume to obtain a single standard stock solution; diluting the single standard stock solution with methanol to obtain a 1 mg / L hexadecyltrimethylammonium chloride-d9 internal standard solution.

[0013] In this invention, the solid-phase extraction process includes: extracting the water sample standard solution to be tested by passing it through a pretreated WCX solid-phase extraction column at a flow rate of 10-14 mL / min.

[0014] In this invention, the pretreatment process of the WCX solid phase extraction column includes: activating the WCX solid phase extraction column sequentially with methanol and water; wherein the flow rate of methanol is 2-4 mL / min and the flow rate of water is 2-4 mL / min.

[0015] In this invention, the elution process includes: after solid-phase extraction, drying the WCX solid-phase extraction column under nitrogen conditions, followed by elution with glacial acetic acid-methanol solution, and after elution, rinsing the WCX solid-phase extraction column with air; in the glacial acetic acid-methanol solution, the volume ratio of glacial acetic acid to methanol is 1:100; the elution flow rate is 0.5-1.5 mL / min; the air flow rate is 9-11 mL / min, and the rinsing time is 8-12 min.

[0016] In this invention, the concentration process includes: placing the eluent obtained above at 35 °C and concentrating it with nitrogen to a volume of <1 mL, then placing it in a sample vial and adding methanol to bring the volume to 1 mL.

[0017] In this invention, the blank solution is purified water.

[0018] In this invention, the gradient elution procedure is as follows: .

[0019] In this invention, the mass spectrometry parameters of the 40 quaternary ammonium salt compounds under the specified mass spectrometry conditions are as follows: .

[0020] This invention also provides the application of the above-mentioned efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry in environmental pollution monitoring.

[0021] The present invention has the following beneficial effects: Compared with traditional LC-MS methods (such as isocratic elution or single ion monitoring), the advantages of this method are: (1) High throughput: 40 QACs can be detected simultaneously in a single injection, covering a variety of structures from short chain (C8) to long chain (C18), and including 21 emerging QACs that have not yet received attention; (2) Anti-interference ability: By optimizing the de-clustering potential, the signal interference of co-extractants such as humic acid and surfactants in complex matrices is effectively suppressed; (3) Environmental friendliness: The methanol-water mobile phase has low toxicity and is in line with the trend of green analytical chemistry.

[0022] The detection method established in this study possesses high sensitivity, wide coverage, and strong anti-interference capabilities, providing a reliable tool for the accurate monitoring of quaternary ammonium salt pollutants in environmental media. Future research can further expand the range of compounds and combine it with non-targeted screening techniques to comprehensively reveal the environmental behavior and health effects of QACs.

[0023] This invention employs a WCX solid-phase extraction column for sample enrichment and purification, and a C18 reversed-phase chromatography column combined with an optimized methanol-water mobile phase gradient elution program to achieve target analyte separation. Multiple reaction monitoring (MRM) is used in positive ion mode with an electrospray ionization source. Specific parent-daughter ion pairs, collision energies, and de-clustering potential parameters were optimized for 40 quaternary ammonium compounds. The method detection limit is 0.1-0.5 μg / L, the quantitation limit is 0.01-200 μg / L, and the correlation coefficient R0 is [not specified]. 2 With a sensitivity of ≥0.995, all target analytes are baseline separated within 20 minutes. It has the advantages of high throughput, high sensitivity, and simple operation, and is suitable for the simultaneous quantitative detection of quaternary ammonium salt pollutants in complex environmental samples.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is the liquid chromatogram of the present invention using the gradient elution program in Table 1; Figure 2 This is a comparison chart of the average response of the target compound when the atomizing gas pressure of this invention is (40-60 psi); Figure 3 This is a comparison chart of the average response of the target compounds at the ion source temperature (450-550℃) of this invention; Figure 4 This is a comparison chart of the average response of the target compound under the nozzle voltage (4000-5000V) of the present invention; Figure 5 These are the detection results of Embodiments 1 and 2 of the present invention; in, Figure 5 In the figure, 'a' represents a comparison of the total concentration of QACs in water samples from municipal wastewater treatment plants and cosmetic wastewater treatment plants. Figure 5 In the figure, b represents the percentage of the four types of QACs in the water sample from the municipal wastewater treatment plant. Figure 5 The figure 'c' represents the percentage of four types of QACs in the wastewater sample from the cosmetics wastewater treatment plant: ATMAC (orange), BAC (blue), DADMAC (green), and emerging QACs (red). Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0027] The quaternary ammonium salt compound standards used in the following experiments were purchased from TMstandard and TRC.

[0028] The dodecyl dimethyl ammonium chloride-d25 standard, tetradecyl dimethyl benzyl ammonium chloride-d7 standard, and hexadecyl trimethyl ammonium chloride-d9 standard were purchased from AmyJet Scientific.

[0029] Mobile phase settings: To optimize chromatographic separation, this invention evaluated two common organic phase systems: a formic acid methanol solution with a volume fraction of 0.1% (based on formic acid volume) and a formic acid acetonitrile solution with a volume fraction of 0.1%. The aqueous phase solutions both consisted of ammonium acetate, formic acid, and water, with an ammonium acetate concentration of 5 mmol / L and a formic acid volume fraction of 0.1%.

[0030] Preliminary experiments show that the methanol-water system can detect all 40 target quaternary ammonium salt compounds. In contrast, while the acetonitrile-water system can significantly shorten the chromatographic retention time of most compounds and generally improve their mass spectrometry response signal, it cannot effectively detect key long-chain dialkyl quaternary ammonium salt homologues (including DADMAC-14, DADMAC-16, and DADMAC-18).

[0031] The optimized gradient elution procedure is shown in Table 1, and the results are shown in Table 2. Figure 1 .

[0032] Table 1 Gradient elution program

[0033] from Figure 1 As can be seen, under the gradient elution program in Table 1, all target compounds achieved baseline separation within 20 minutes (retention time range: 0.5-18.6 min). Each chromatographic peak was sharp and symmetrical (half-peak width ≤ 0.3 min), and the resolution between adjacent peaks was > 1.5. In particular, the structural homologues ATMAC-8 / 10 / 12 / 14 / 16 / 18 series, BAC-8 / 10 / 12 / 14 / 16 / 18, and DADMAC-8 / 10 / 12 / 14 / 16 / 18 series all exhibited clear baseline separation. The system maintained a good response across a wide range of compound polarities, from DADMAC-8 to DADMAC-18; for example, DADMAC-16 and DADMAC-18 could only be detected at 100% B phase. The entire analytical process maintained a stable baseline (noise level < 5000), and key compounds such as CPB and DADMAC-14, and BTBAC and TMABC, which are easily co-eluted, were completely separated (resolution R > 2.0). This method, through gradient elution program optimization, successfully resolved the peak tailing problem caused by differences in surface activity in quaternary ammonium salt compounds (symmetry factor 0.95–1.05), providing a reliable technical solution for the simultaneous and accurate quantification of multi-component quaternary ammonium salts in complex matrices.

[0034] Mass spectrometry condition optimization: Collision energy and de-clustering potential settings: This method also successfully achieved efficient and simultaneous separation and detection of 40 quaternary ammonium salt compounds by systematically optimizing the liquid chromatography gradient program and mass spectrometry parameters. Quaternary ammonium salt compounds are tetravalent nitrogen cations that often form stable salts with halide anions. In full scan mode, the parent ion was mainly R4N after dehalogenation. + Ions. In the mode where standards are directly introduced into the mass spectrometer, the daughter ions, collision energies, and de-clustering potentials of each quaternary ammonium salt compound were obtained, as shown in Table 2.

[0035] Table 2 Mass Spectrometry Condition Optimization Table

[0036] As can be seen from Table 2, the three main types of typical quaternary ammonium salts exhibit similar ionic fragments after cleavage. For example, BAC-type quaternary ammonium salts all contain benzyl fragments (m / z = 91.1), while ATMAC and DADMAC fragments are more numerous, but two fragments with higher response values ​​exist, m / z = 57.1 and m / z = 60.

[0037] Ion source parameters: To obtain the highest quality spectral detection sensitivity, this invention optimized three key ion source parameters: nozzle voltage, nebulizing gas pressure, and ion source temperature. The results are shown in [Figure number missing]. Figures 2-4 A comprehensive evaluation was conducted based on nozzle voltage (4000-5000V), atomizing gas pressure (40-60 psi), and ion source temperature (450-550℃). It was found that a nozzle voltage of 5000V... Figure 4 Most compounds showed the highest response at a pressure of 50 psi, and also at a pressure of 50 psi. Figure 2 Most compounds showed the highest response; most compounds showed the highest response at an ion source temperature of 550℃. Figure 3 Based on the above results, an optimized combination of ion source parameters was finally established: nozzle voltage 5000V, nebulizing gas pressure 50psi, and ion source temperature 500℃. This set of parameters has been confirmed to enable most target quaternary ammonium salt compounds to reach their maximum response intensity, and therefore has been established as the standard configuration for the entire analytical method.

[0038] Sensitivity and linear range: By employing multiple reaction monitoring (MRM) mode combined with optimized ion source parameters (Table 2), matrix interference was significantly reduced (noise value <5000), and detection sensitivity was improved. Standard curve results showed that all 40 target analytes exhibited good linearity (R0.05) within the concentration range of 0.1–200 μg / L. 2 =0.98-0.99, indicating that this method is suitable for the quantitative analysis of trace quaternary ammonium salts. Figure 2 Based on a signal-to-noise ratio of 3x (S / N=3) and 10x (S / N=10), the limits of detection (LOD) for each compound are 0.1-0.5 μg / L, and the limits of quantitation (LOQ) are 0.1-200 μg / L, with particularly outstanding ability to detect low-abundance components.

[0039] Method verification: A high-concentration mother liquor was prepared by dissolving quaternary ammonium salt compound standards (see Table 2 for the types of quaternary ammonium salt compounds) in methanol. The high-concentration mother liquor was then further diluted with methanol to obtain a mixed quaternary ammonium salt mother liquor. The concentration of all 40 quaternary ammonium salt compounds in the mixed quaternary ammonium salt mother liquor was 1 mg / L.

[0040] The didodecyl dimethyl ammonium chloride-d25 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L didodecyl dimethyl ammonium chloride-d25 internal standard solution.

[0041] Tetradecyl dimethyl benzyl ammonium chloride-d7 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution.

[0042] The hexadecyltrimethylammonium chloride-d9 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L hexadecyltrimethylammonium chloride-d9 internal standard solution.

[0043] Add 50 μL of the prepared quaternary ammonium salt mixed stock solution to 100 mL of water to obtain the water sample to be tested. Then add 50 μL of dodecyl dimethyl ammonium chloride-d25 internal standard solution, 50 μL of tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution, and 50 μL of hexadecyl trimethyl ammonium chloride-d9 internal standard solution, shake well and set aside to obtain the standard solution of the water sample to be tested.

[0044] A WCX solid-phase extraction column (500 mg, 6 cc, CNW, China) was pretreated sequentially with 6 mL of methanol and 6 mL of deionized water at a flow rate of 3 mL / min. After pretreatment, the prepared water sample standard solution was extracted through the WCX solid-phase extraction column at a flow rate of 12 mL / min. After extraction, the solid-phase extraction column was dried under nitrogen for 25 min. Then, the target analyte was eluted with two 5 mL aliquots of 1% glacial acetic acid-methanol solution (v:v = 1:100) at a flow rate of 1 mL / min. After elution, the column was flushed with 10 mL of air at a flow rate of 10 mL / min to remove residual methanol. The collected eluent was concentrated under nitrogen at 35 °C to a volume less than 1 mL, then transferred to a 2 mL white plastic autosampler vial, and methanol was added to bring the volume to 1 mL to obtain the test solution.

[0045] The above-mentioned test solution was injected into a high-performance liquid chromatography-tandem mass spectrometry system for analysis.

[0046] The chromatographic conditions were as follows: Column: Agilent C18 analytical column (ZORBAX Eclipse Plus C18 column (100×3.0 mm, 1.7 μm), analytical column temperature set at 45℃. Mobile phase A was an aqueous solution composed of ammonium acetate, formic acid, and water, with an ammonium acetate concentration of 5 mmol / L and a formic acid volume fraction of 0.1%; Mobile phase B was a formic acid methanol solution with a formic acid volume fraction of 0.1%, a flow rate of 0.45 mL / min, and a gradient elution program identical to that in Table 1.

[0047] Mass spectrometry conditions were as follows: positive ion mode of electrospray ionization source, multiple reaction monitoring (MRM); nebulizer gas temperature 450℃; nebulizer gas pressure 50 psi; auxiliary gas pressure 50 psi; nozzle voltage 5000 V; collision gas pressure 8 psi; curtain gas pressure 20 psi; segmented acquisition mode; isolation time window 0.5 min. The mass spectrometry parameters of the 40 quaternary ammonium salt compounds are the same as those in Table 2.

[0048] The separation results are as follows Figure 1 As shown, from Figure 1 It can be seen that the 40 QACs can be completely separated. Through quantitative calculation of the recovery rate, the spiked recovery rate of the 40 QACs is between 82.5% and 118.3%, and the relative standard deviation (RSD) is between 1.2% and 14.8%, indicating that the method has good accuracy and precision.

[0049] Example 1 The following steps were taken for systematic quantitative analysis of QACs (qualitative analytes) in influent samples from municipal wastewater treatment plants: Preparation of internal standard solution: The didodecyl dimethyl ammonium chloride-d25 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L didodecyl dimethyl ammonium chloride-d25 internal standard solution.

[0050] Tetradecyl dimethyl benzyl ammonium chloride-d7 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution.

[0051] The hexadecyltrimethylammonium chloride-d9 standard was dissolved in methanol and diluted to volume to obtain a single standard stock solution; the single standard stock solution was diluted with methanol to obtain a 1 mg / L hexadecyltrimethylammonium chloride-d9 internal standard solution.

[0052] S1. Filter the water sample to be tested through a glass fiber filter (0.45μm, Jinteng, China) to obtain a pretreated water sample. Take 100mL of the pretreated water sample using a graduated cylinder, and then add 50μL of 1 mg / L dodecyl dimethyl ammonium chloride-d25 internal standard solution, 50μL of 1 mg / L tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution, and 50μL of 1 mg / L hexadecyl trimethyl ammonium chloride-d9 internal standard solution to obtain the standard solution of the water sample to be tested.

[0053] A high-concentration stock solution was prepared by dissolving quaternary ammonium salt compound standards (see Table 2 for the types of quaternary ammonium salt compounds) in methanol. This stock solution was then further diluted with methanol to obtain a mixed quaternary ammonium salt stock solution, in which the concentration of each of the 40 quaternary ammonium salt compounds was 1 mg / L. This mixed stock solution was then further diluted to obtain a series of standard curve samples with different concentrations. 50 μL of 1 mg / L dodecyl dimethyl ammonium chloride-d25 internal standard solution, 50 μL of 1 mg / L tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution, and 50 μL of 1 mg / L hexadecyl trimethyl ammonium chloride-d9 internal standard solution were added to each standard curve sample to plot a standard curve with a concentration range of 0.1–200 µg / L.

[0054] A WCX solid-phase extraction column (500 mg, 6 cc, CNW, China) was pretreated sequentially with 6 mL of methanol and 6 mL of deionized water at a flow rate of 3 mL / min. After pretreatment, the prepared standard solution of the water sample and the blank solution (pure water) were extracted through the WCX solid-phase extraction column at a flow rate of 12 mL / min. After extraction, the solid-phase extraction column was dried under nitrogen for 25 min. Then, the target analyte in the column was eluted with two 5 mL aliquots of 1% glacial acetic acid-methanol solution (v:v = 1:100) at a flow rate of 1 mL / min. After elution, the column was flushed with 10 mL of air at a flow rate of 10 mL / min to remove residual methanol. The collected eluent was concentrated under nitrogen at 35 °C to a volume less than 1 mL, then transferred to a 2 mL white plastic autosampler vial, and methanol was added to bring the volume to 1 mL to obtain the test solution.

[0055] S2. Inject the above-mentioned test solution into a high-performance liquid chromatography-tandem mass spectrometry system for analysis.

[0056] The chromatographic conditions were as follows: Column: Agilent C18 analytical column (ZORBAX Eclipse Plus C18 column (100×3.0 mm, 1.7 μm), analytical column temperature set at 45℃. Mobile phase A was an aqueous solution composed of ammonium acetate, formic acid, and water, with an ammonium acetate concentration of 5 mmol / L and a formic acid volume fraction of 0.1%; Mobile phase B was a formic acid methanol solution with a formic acid volume fraction of 0.1%, a flow rate of 0.45 mL / min, and a gradient elution program identical to that in Table 1.

[0057] Mass spectrometry conditions were as follows: positive ion mode of electrospray ionization source, multiple reaction monitoring (MRM); nebulizer gas temperature: 450℃; nebulizer gas pressure: 50 psi; auxiliary gas pressure: 50 psi; nozzle voltage: 5000 V; collision gas pressure: 8 psi; curtain gas pressure: 20 psi; segmented acquisition mode, isolation time window: 0.5 min.

[0058] Example 2 This embodiment tested QACs monomers in effluent samples from a cosmetic wastewater treatment plant, and the detection method was the same as in Example 1.

[0059] The detection results of Examples 1 and 2 above are as follows: Figure 5 As shown in Table 3.

[0060] Table 3. Detection results of Examples 1 and 2

[0061] From Table 3 and Figure 5 It can be seen that the total concentration of QACs in the municipal wastewater influent was 3865.3 ng / L, significantly higher than the 1621.9 ng / L in the effluent from the cosmetic wastewater treatment plant. In terms of component distribution, the four major categories of ATMAC, BAC, emerging QACs, and DADMAC accounted for 44.9%, 25.5%, 20.0%, and 9.6% respectively in the municipal wastewater, showing a relatively balanced composition. In contrast, the cosmetic wastewater treatment plant effluent was dominated by ATMAC, accounting for a high 76.9%, while the other categories each accounted for less than 11%. At the monomer level, Table 3 shows that the core dominant monomers in the municipal wastewater were ATMAC-18 (987.95 ng / L), BAC-12 (679.49 ng / L), and ATMAC-16 (636.79 ng / L), which together contributed over 60% of the total concentration. The core monomers in the cosmetic wastewater treatment plant effluent were ATMAC-18 (830.28 ng / L) and ATMAC-16 (411.84 ng / L). The concentrations of QACs (121.52 ng / L) and BAC-18 (121.52 ng / L) together accounted for over 85% of the total concentration. High concentrations of BAC-12 in municipal wastewater were not detected in cosmetic wastewater, indicating significant differences in the characteristic monomers between the two types of water samples. These results demonstrate that this method can accurately quantify multiple categories of QACs in actual water bodies, clearly elucidating their concentration levels, compositional characteristics, and source differences. It is suitable for screening and source tracing analysis of emerging QACs pollutants in complex aquatic environments.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-efficiency detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry, characterized in that, Includes the following steps: S1. Add 50 μL of dodecyl dimethyl ammonium chloride-d25 internal standard solution, 50 μL of tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution, and 50 μL of hexadecyl trimethyl ammonium chloride-d9 internal standard solution to 100 mL of pretreated water sample to obtain the water sample standard solution. Perform solid phase extraction, elution, and concentration on the water sample standard solution to obtain the test solution. S2. Plot a standard curve, then inject the test solution and blank solution into a high performance liquid chromatography-tandem mass spectrometry system for analysis. Adjust the chromatographic and mass spectrometry conditions to obtain the contents of 40 quaternary ammonium salt compounds. The quaternary ammonium salt compound is a tetravalent nitrogen cationic compound; The chromatographic conditions used were as follows: a C18 reversed-phase column; gradient elution program; mobile phase A was an aqueous solution composed of ammonium acetate, formic acid, and water; the concentration of ammonium acetate in the aqueous solution was 5 mmol / L, and the volume fraction of formic acid was 0.1%; mobile phase B was a methanolic solution of formic acid with a volume fraction of 0.1%; the flow rate was 0.4-0.5 mL / min; and the column temperature was 40-50℃. The mass spectrometry conditions were set under positive ion mode of electrospray ionization source, using multiple reaction monitoring; the nebulizer gas temperature was 450℃; the nebulizer gas pressure was 50psi; the auxiliary gas pressure was 50psi; and the nozzle voltage was 5000V. The impact pressure is 8 psi; The air curtain pressure is 20 psi; The segmented acquisition mode has an isolation time window of 0.5 minutes.

2. The method for efficient detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The tetravalent nitrogen-cationic compounds include diallyl dimethyl ammonium chloride, 1-butyl-1-methylpyrrolidone onium chloride, (3-carboxypropyl)trimethyl ammonium chloride, benzyltrimethylammonium bromide, 1-butyl-3-methylimidazolium chloride, (5-bromopentyl)trimethylammonium bromide, benzyltributylammonium chloride, benzyltriethylammonium bromide, S-butyrylthiocholine iodide, tetrapropylammonium bromide, 1-hexyl-3-methylimidazolium chloride, dodecylethyldimethylammonium bromide, 1,2-dimethyl-3,5-diphenylpyrazoleonium methyl sulfate, hexyldimethylbenzylammonium chloride, octyltrimethylammonium chloride, octyldimethylbenzylammonium chloride, decyltrimethylammonium bromide, decyldimethylbenzylammonium chloride, and dodecyltrimethylammonium chloride. Ammonium, didodecyl dimethyl ammonium bromide, dioctyl dimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride, tetradecyl trimethyl ammonium chloride, dodecyl dimethyl (2-phenoxyethyl) ammonium bromide, decyl dimethyl octyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium chloride, didecyl dimethyl ammonium chloride, hexadecylpyridinium bromide, methyl trioctyl ammonium chloride, tetraheptyl ammonium bromide, benzyl dimethyl hexadecyl ammonium chloride, octadecyl trimethyl ammonium chloride, octadecyl dimethyl benzyl ammonium chloride, dimethyl ditetradecyl ammonium bromide, dimethyl dioctadecyl ammonium bromide, dihexadecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium chloride, 1-decyl-3-methylimidazolium chloride, benzyl ammonium chloride.

3. The method for efficient detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The pretreatment process of the water sample to be tested includes: filtering the water sample through a glass fiber filter membrane with a pore size of 0.45 μm to obtain the pretreated water sample to be tested.

4. The efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The concentration of the bis(dodecyl)dimethylammonium chloride-d25 internal standard solution was 1 mg / L; The concentration of the tetradecyl dimethyl benzyl ammonium chloride-d7 internal standard solution is 1 mg / L; The concentration of the hexadecyltrimethylammonium chloride-d9 internal standard solution is 1 mg / L.

5. The method for efficient detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The solid-phase extraction process includes: The standard solution of the water sample to be tested was extracted by passing it through a pretreated WCX solid phase extraction column at a flow rate of 10-14 mL / min.

6. The efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 5, characterized in that, The pretreatment process of the WCX solid phase extraction column includes: activating the WCX solid phase extraction column sequentially with methanol and water; The flow rate of methanol is 2-4 mL / min, and the flow rate of water is 2-4 mL / min.

7. The method for efficient detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The elution process includes: after solid-phase extraction is completed, the WCX solid-phase extraction column is dried under nitrogen conditions, then eluted with glacial acetic acid-methanol solution, and after elution is completed, the WCX solid-phase extraction column is purged with air. In the glacial acetic acid-methanol solution, the volume ratio of glacial acetic acid to methanol is 1:100; the elution flow rate is 0.5-1.5 mL / min; the air flow rate is 9-11 mL / min, and the rinsing time is 8-12 min.

8. The method for efficient detection of 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, The gradient elution procedure is as follows: 。 9. The efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry according to claim 1, characterized in that, Under the aforementioned mass spectrometry conditions, the mass spectrometry parameters for the 40 quaternary ammonium salt compounds are as follows: 。 10. The application of the efficient detection method for 40 quaternary ammonium salt compounds based on liquid chromatography-mass spectrometry as described in any one of claims 1-9 in environmental pollution monitoring.

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