Method for detecting sodium dodecyl benzene sulfonate in a plant sample

Abstract

This application provides a method for detecting sodium dodecylbenzenesulfonate (SDBS) in plant samples, comprising: washing, freeze-drying, pulverizing and sieving the plant sample to obtain plant sample powder; performing multiple ultrasonic-assisted extractions on the plant sample powder using a methanol-water mixed solvent; combining and collecting the extracts; diluting the combined extracts with water; loading the extracts onto a weak anion exchange solid-phase extraction column for purification; eluting with ammonium acetate buffer solution; eluting with an organic solvent containing alkaline components; collecting the eluent containing the target analyte; concentrating the eluent to near dryness under controlled temperature conditions with nitrogen blowing; redissolving the eluent; filtering the eluent through a filter membrane to obtain the test solution; and qualitatively and quantitatively analyzing the sodium dodecylbenzenesulfonate in the test solution using liquid chromatography-tandem mass spectrometry (LC-MS / MS). This invention overcomes the interference of complex components in the plant matrix through a specific extraction system and selective purification, achieving quantitative analysis of SDBS.

Description

Technical Field

[0001] This invention relates to the fields of analytical chemistry and environmental testing technology, and in particular to a method for detecting sodium dodecylbenzenesulfonate in plant samples. Background Technology

[0002] Sodium dodecylbenzenesulfonate (SDBS), a typical synthetic anionic surfactant, is widely used in detergents, industrial production, and daily chemical products. Its extensive use and emissions have led to its prevalent presence in various environmental media, and it may enter plants through adsorption and absorption, posing a potential threat to agricultural product safety and ecosystem health. Therefore, establishing an accurate and stable analytical method for detecting SDBS in plant samples is of great significance for conducting environmental pollution assessments, plant physiological and toxicological research, and food safety monitoring.

[0003] Currently, conventional detection techniques for SDBS mainly include methylene blue spectrophotometry, direct two-phase titration, flow injection analysis, and high-performance liquid chromatography (HPLC). While traditional chemical methods like methylene blue spectrophotometry are simple to operate, their principle is based on the universal reaction between anionic surfactants and colorimetric reagents, measuring the content of "total anionic surfactants" and failing to specifically identify and accurately quantify SDBS. In practical applications, these methods exhibit poor selectivity and are highly susceptible to severe interference from coexisting inorganic salt ions, other types of surfactants, and complex organic matrices in the sample, leading to significant deviations in detection results, especially in samples with low concentrations or high background interference. Their accuracy and repeatability often fail to meet the requirements of modern trace analysis. Although some HPLC methods improve selectivity to some extent through chromatographic separation, their commonly configured UV or fluorescence detectors are essentially universal detectors, and their ability to distinguish between structurally similar compounds or co-extracted matrices remains limited. More importantly, to deal with complex samples, these chromatographic methods often rely on lengthy and demanding pretreatment steps to purify the samples, resulting in low efficiency of the entire analytical process.

[0004] In recent years, liquid chromatography-tandem mass spectrometry (LC-MS / MS) has become a powerful tool for the analysis of trace organic pollutants due to its high separation efficiency, high selectivity, and high sensitivity. However, most existing publicly available LC-MS / MS detection schemes focus on the detection of SDBS in environmental samples such as water and wastewater. For plant samples, a special and complex biological matrix, existing technologies lack systematic and mature solutions. Plant tissues (especially roots) contain a large amount of chlorophyll, lipids, organic acids, pigments, and natural surfactants. These components can co-dissolve with the target analyte during extraction and produce severe matrix effects in subsequent mass spectrometry analysis, leading to signal suppression or enhancement of the target analyte, which seriously affects the stability and accuracy of quantification. Therefore, developing a method that can effectively overcome complex matrix interference and achieve efficient extraction, purification, and stable quantification of SDBS in plant samples is a pressing technical problem to be solved in the field of environmental analysis. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention effectively overcomes the interference of pigments, organic acids, and other substances in plant matrices through a specific extraction system and selective purification steps, achieving highly selective, highly sensitive, and stable and reliable quantitative analysis of SDBS, and is suitable for the accurate detection of this pollutant in complex plant samples.

[0006] This invention provides a method for detecting sodium dodecylbenzenesulfonate in plant samples, comprising: S1. Sample pretreatment: The plant sample is cleaned, freeze-dried, pulverized and sieved to obtain plant sample powder; S2. Extraction: The plant sample powder was subjected to multiple ultrasonic-assisted extractions using a methanol-water mixed solvent, and the extracts were combined and collected. S3. Solid-phase extraction purification: Dilute the combined extract with water, load it onto a weak anion exchange solid-phase extraction column, and then rinse with ammonium acetate buffer solution. After rinsing, elute with an organic solvent containing alkaline components and collect the eluent containing the target analyte. S4. Concentration and Redissolution: The collected eluent was concentrated to near dryness by nitrogen blowing at a temperature not exceeding 45°C, and then redissolved in ultrapure water to a volume of 1.5 mL. The eluent was then filtered through a 0.22 μm microporous membrane to obtain the test solution. S5. Detection: Sodium dodecylbenzenesulfonate in the test solution was qualitatively and quantitatively analyzed using a liquid chromatography-tandem mass spectrometry system. Chromatographic separation was performed using a reversed-phase column, and mass spectrometry detection was performed using an electrospray ionization source in negative ion mode with multiple reaction monitoring for data acquisition. Quantification was performed using the external standard method.

[0007] Furthermore, in step S2, the volume ratio of methanol to water in the methanol-water mixed solvent is 6-9:1-4.

[0008] Furthermore, the volume ratio of methanol to water in the methanol-water mixed solvent is 8:2.

[0009] Furthermore, the conditions for ultrasound-assisted extraction in step S2 are as follows: the same sample powder is extracted repeatedly 3 to 5 times, and the extraction time for each extraction is 10 to 30 minutes.

[0010] Furthermore, in step S3, the volume fraction of the organic phase after dilution with water in the combined extract is no higher than 20%.

[0011] Furthermore, the weak anion exchange solid-phase extraction column described in step S3 is activated sequentially with 0.1% ammonia-methanol solution, methanol, and ultrapure water before sample loading.

[0012] Furthermore, the concentration of the ammonium acetate buffer solution in step S3 is 25 mmol / L and the pH of the solution is 4.0.

[0013] Furthermore, the organic solvent containing the alkaline component in step S3 is a 0.1% ammonia-methanol solution.

[0014] Furthermore, the microporous filter membrane material mentioned in step S4 is polytetrafluoroethylene, nylon, or other materials suitable for aqueous systems.

[0015] Further, the reversed-phase chromatographic column mentioned in step S5 includes, but is not limited to, a C8 chromatographic column; the C8 chromatographic column uses isocratic elution in chromatographic separation, mobile phase A is a 20 mmol / L ammonium formate aqueous solution containing 0.1% formic acid, mobile phase B is acetonitrile, the volume ratio of phase A to phase B is 20:80, the flow rate is 0.2 mL / min, the column temperature is 40℃, and the injection volume is 5 μL; the fragmentation voltage of the mass spectrometry detection is 380V, the collision energy is 35eV, the capillary voltage is 3500V, the gas temperature is 350℃, the gas flow rate is 10 L / min, the nebulizer pressure is 20 psi, and the residence time is 1000 ms.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) To address the severe interference caused by high concentrations of endogenous substances such as pigments, lipids, and organic acids in plant samples to the detection of target analytes, the extraction solvent was optimized and combined with weak anion exchange solid-phase extraction technology to specifically adsorb and elute the target analytes, efficiently removing most of the endogenous interfering substances such as pigments and organic acids in plant samples, minimizing the matrix effect in mass spectrometry detection, and ensuring high selectivity of the detection results.

[0017] 2) Combining efficient pretreatment with LC-MS / MS, this method achieves accurate identification and quantification of SDBS in complex environments. The method detection limit (LOD) is 0.01 mg / L, the quantitation limit (LOQ) is 0.05 mg / L, the correlation coefficient r>0.999 in the linear range of 0.05~10 mg / L, the intra-day and inter-day precision RSD are both less than 5%, and the spiked recovery rate is between 87.5% and 108.2%, which fully meets the stringent requirements for trace contaminant analysis in complex samples.

[0018] 3) This method does not rely on complex chemical derivatization steps and significantly reduces the use of toxic reagents. Key operating parameters are controlled, the process is simple and reproducible, and the requirements for instruments, equipment and personnel operating skills are fully compatible with the conditions of conventional analytical laboratories. It is easy to convert into a standard method and promote its application.

[0019] 4) This method not only demonstrates excellent linearity, repeatability, recovery, and precision in standard solution systems, but has also been successfully applied and validated in actual plant samples (such as bean roots) and environmental water samples with complex biological backgrounds. It achieves stable and accurate quantification of SDBS in different matrices, proving its strong anti-interference ability and wide applicability, effectively serving plant-pollutant interaction studies, environmental exposure assessments, and related monitoring and detection work. Attached Figure Description

[0020] Figure 1 The flowchart illustrates the steps of a method for detecting sodium dodecylbenzenesulfonate in plant samples, as provided in this embodiment of the invention.

[0021] Figure 2 To optimize the MRM chromatogram of SDBS under LC–MS / MS conditions. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in 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 this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0023] Please see Figure 1 , Figure 1 A flowchart illustrating the steps of a method for detecting sodium dodecylbenzenesulfonate in plant samples provided by an embodiment of the present invention is shown below. S1. Sample pretreatment: The plant sample is cleaned, freeze-dried, pulverized and sieved to obtain plant sample powder; S2. Extraction: The plant sample powder was subjected to multiple ultrasonic-assisted extractions using a methanol-water mixed solvent, and the extracts were combined and collected. S3. Solid-phase extraction purification: Dilute the combined extract with water, load it onto a weak anion exchange solid-phase extraction column, and then rinse with ammonium acetate buffer solution. After rinsing, elute with an organic solvent containing alkaline components and collect the eluent containing the target analyte. S4. Concentration and Redissolution: The collected eluent was concentrated to near dryness by nitrogen blowing at a temperature not exceeding 45°C, and then redissolved in ultrapure water to a volume of 1.5 mL. The eluent was then filtered through a 0.22 μm microporous membrane to obtain the test solution. S5. Detection: Sodium dodecylbenzenesulfonate in the test solution was qualitatively and quantitatively analyzed using a liquid chromatography-tandem mass spectrometry system. Chromatographic separation was performed using a reversed-phase column, and mass spectrometry detection was performed using an electrospray ionization source in negative ion mode with multiple reaction monitoring for data acquisition. Quantification was performed using the external standard method.

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] Example 1 Instruments, reagents and standard solution preparation (1) Instruments and reagents Main instruments: freeze dryer, analytical balance, ultrasonic cleaner, centrifuge, solid-phase extraction device, nitrogen blow-through concentrator, ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry system; among which, the solid-phase extraction column is a Waters OasisWAX weak anion exchange column (6 cc / 150 mg), and the liquid chromatography-tandem mass spectrometry system is an Agilent 1290 Infinity II ultra-high performance liquid chromatograph coupled with an Agilent 6470 triple quadrupole mass spectrometer (Agilent Technologies, Inc.), equipped with an electrospray ionization source (ESI).

[0026] Main reagents: Sodium dodecylbenzenesulfonate standard (purity >98%), methanol and acetonitrile are HPLC grade, ammonium formate, ammonium acetate, glacial acetic acid and ammonia are analytical grade or higher, and the experimental water is ultrapure water (18.25 MΩ·cm).

[0027] Solid phase extraction column: Weak anion exchange (WAX) solid phase extraction column.

[0028] (2) Preparation of standard solutions Accurately weigh a certain amount of sodium dodecylbenzenesulfonate (SDBS) standard, dissolve it in ultrapure water and dilute to volume to prepare a 10 mg / L standard stock solution, and store it at 4°C protected from light. Before use, dilute the standard stock solution stepwise with ultrapure water to prepare a series of working solutions of different concentrations for establishing calibration curves and validating methodological performance.

[0029] (3) Quantitative methods Quantitative analysis was performed using the external standard method. A series of standard working solutions were injected and analyzed under predetermined instrument conditions. A calibration curve was established by linear regression of the peak area (y) of the target compound against its mass concentration (x, mg / L). The SDBS content in the sample was calculated from the calibration curve. Each concentration level of standard solution and sample solution was injected three times, and the average peak area was used for quantitative calculation.

[0030] Example 2 Liquid chromatography-tandem mass spectrometry analysis conditions Chromatographic separation was performed using a Zorbax Eclipse XDB-C8 column under isocratic elution conditions. Mass spectrometry detection was performed using an electrospray ionization (ESI) source in negative ion mode with multiple reaction monitoring (MRM) for data acquisition. The HPLC conditions and mass spectrometry detection parameters are shown in Table 1.

[0031] Sodium dodecylbenzenesulfonate (SDBS) contains sulfonic acid groups in its molecular structure, making it prone to deprotonation in electrospray ionization (ESI) to generate stable negative ions. Therefore, in this embodiment of the invention, chromatographic separation was performed using a Zorbax Eclipse XDB-C8 column under isocratic elution conditions, and mass spectrometry detection was performed using an ESI source in negative ion mode with multiple reaction monitoring (MRM) data acquisition. Experiments show that SDBS readily undergoes deprotonation in ESI... - The main precursor ion generated in this mode is m / z 325 ([M H] - After collision-induced dissociation, it produces a characteristic fragment ion m / z183 with strong response and good reproducibility. This ion has been confirmed as a typical product ion of straight-chain alkylbenzene sulfonates and is suitable for quantitative analysis.

[0032] In the process of establishing the method, the embodiments of this invention systematically optimized the detection conditions of liquid chromatography and mass spectrometry. The effects of parameters such as column type, mobile phase composition and ratio, flow rate, and column temperature on the retention behavior and peak shape of the target analyte were investigated. Simultaneously, mass spectrometry parameters such as ion source polarity, MRM ion pair, fragmentation voltage, and collision energy were compared and adjusted. The results show that under the optimized chromatographic conditions, SDBS can achieve effective separation in a shorter time, with symmetrical peak shapes, stable retention times, and no significant interfering peaks. The detected peak shape is as follows: Figure 2As shown in Table 1, the optimal liquid chromatography conditions and mass spectrometry detection parameters, considering both separation performance, sensitivity, and stability, were determined.

[0033] Table 1 Chromatographic and mass spectrometric conditions for LC-MS / MS determination of SDBS Example 3 Methodological Validation (1) Linear range and sensitivity Under the optimized LC-MS / MS conditions in Example 2, a series of standard working solutions (0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 4, 6, 8, 10 mg / L) were analyzed. Linear regression was performed on the peak area (y) of the target compound against the mass concentration (x, mg / L), and the linear performance index is shown in Table 2.

[0034] Table 2 Calibration curves and linear performance parameters of SDBS The results in Table 2 show that SDBS exhibits good linearity in the concentration range of 0.05–10 mg / L, with the linear equation being y = 101987x - 18497 and the correlation coefficient r = 0.9995.

[0035] To evaluate the sensitivity of the established LC-MS / MS method, the limits of detection (LOD) and quantitation (LOQ) of the target compound were assessed using a standard solution system. Multiple repeated measurements were performed using a low-concentration SDBS standard solution within the linear range, and the LOD and LOQ were calculated based on the instrument signal-to-noise ratio (S / N). Specifically, the LOD was calculated at the concentration corresponding to an S / N = 3, and the LOQ was calculated at the concentration corresponding to an S / N = 10. The proposed method showed a LOD of 0.01 mg / L and a LOQ of 0.05 mg / L for SDBS, indicating high detection sensitivity.

[0036] (2) Repeatability To evaluate the repeatability of the established LC-MS / MS method, SDBS standard solutions at low, medium, and high concentration levels (0.2, 1.0, and 8.0 mg / L) were selected for repeated determination under optimized analytical conditions. Each concentration level of standard solution was injected seven times consecutively under the same experimental conditions, and the results were recorded. Peak areas were measured, and the mean, standard deviation (SD), and relative standard deviation (RSD) were calculated to evaluate the repeatability of the method. The results are shown in Table 3.

[0037] Table 3. Repeatability evaluation results of the SDBS quantitative analysis method The results in Table 3 show that the RSDs for the three concentration levels of 0.2, 1.0, and 8.0 mg / L were 1.34%, 0.74%, and 0.99%, respectively, all less than 5%, indicating that the method has good repeatability.

[0038] (3) Spiking recovery and precision To evaluate the quantitative reliability of the established LC-MS / MS method under external standard quantification conditions, this study conducted spike recovery experiments in a standard solution system and calculated the relative standard deviation (RSD). SDBS standard solutions at low, medium, and high concentration levels (0.2, 1.0, and 8.0 mg / L) were selected as reference solutions within the linear range. Known amounts of SDBS standard working solution (100 mg / L) were added to these solutions, resulting in theoretical spike concentration increments ΔC of 0.2, 1.0, and 2.0 mg / L, respectively. Spike recoveries were measured and calculated under the same conditions. The spike recovery rate was calculated according to equation (1), and the spike recovery rate and RSD results are shown in Table 4.

[0039] In the formula, The concentration was measured using the reference solution. The concentration measured after spiking is given. ΔC is the theoretical spiking concentration increment, and its specific value is determined based on the spiking volume and the final volume.

[0040] Table 4. Results of spiked recovery and precision (RSD) evaluation of the SDBS quantitative analysis method. The results in Table 4 show that the average recoveries at the three spiking levels were 88.80%, 98.34%, and 102.25%, with RSDs of 5.94%, 2.24%, and 5.13%, respectively. This indicates that the method has good accuracy and precision in the standard solution system and meets the requirements for trace quantitative analysis.

[0041] Example 4 Detection of sodium dodecylbenzenesulfonate (SDBS) in plant root samples.

[0042] This embodiment uses the root system of common bean after SDBS exposure culture as the analysis object to explain in detail the complete application process of the method of the present invention in complex plant substrates.

[0043] (1) Sample pretreatment ① Sample pretreatment: Collect bean root samples and rinse repeatedly with sufficient deionized water to remove surface adhering substances. After blotting off the surface moisture with clean paper, place the samples in freeze dryer cryovials and freeze-dry at -80℃ for at least 48 hours until constant weight. Place the dried samples in a stainless steel grinding device to pulverize them and pass them through a 60-mesh metal sieve to obtain uniform plant root powder, which is then stored in a desiccator for later use.

[0044] ② Sample Extraction: Accurately weigh 0.10 g (accurate to 0.1 mg) of dried plant root powder into a 50 mL polypropylene centrifuge tube. Add 10.0 mL of methanol-water mixed extraction solvent (methanol to water volume ratio of 8:2). Place the centrifuge tube in an ultrasonic cleaner and extract ultrasonically at 25℃ and 40 kHz for 20 minutes. Centrifuge and collect the supernatant. Add 10.0 mL of the same extraction solvent to the residue again, and repeat the above ultrasonic and centrifugation operations for a total of 3 extractions. Combine all supernatants. Centrifuge the combined extract at 4000 r / min for 10 min and collect the supernatant for later use.

[0045] ③ Extract dilution: Dilute the combined centrifuged extracts with ultrapure water to control the volume fraction of methanol in the mixture below 20% in order to reduce the impact of organic phase on the retention performance of the subsequent solid phase extraction column.

[0046] ④ Solid-phase extraction purification: Install a weak anion exchange solid-phase extraction column on a solid-phase extraction device, and activate the column sequentially with a methanol solution containing 0.1% ammonia, methanol, and ultrapure water, keeping the column bed moist during activation. Load the diluted sample extract onto the activated column at a flow rate of approximately 0.10~0.15 mL / s. After loading, rinse the column with eluent (25 mmol / L ammonium acetate buffer solution, adjusted to pH 4.0 with glacial acetic acid) to remove weakly retained or non-ionic interfering substances such as pigments and organic acids. After rinsing, vacuum dry the column to remove residual moisture. After drying, elute the target compound SDBS sequentially with methanol and 0.1% ammonia-methanol solution, and collect the eluent.

[0047] ⑤ Concentration and Reconstitution: The collected eluent was placed in a 40°C water bath and concentrated to near dryness (no flowing liquid in the tube) by a gentle nitrogen stream. It was then reconstituted with ultrapure water to 1.5 mL. The resulting solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) microporous membrane and transferred to a 2 mL liquid chromatography vial for analysis.

[0048] (2) LC-MS / MS analysis results The treated root samples were analyzed under the same LC-MS / MS conditions as in Example 2. The content of sodium dodecylbenzenesulfonate in the samples was quantified using the external standard method. The same sample was measured in parallel three times, and the results are shown in Table 5.

[0049] Table 5. Quantitative analysis of SDBS in real plant root samples and evaluation of method applicability. As shown in Table 5, the average relative standard deviation of the measured concentration of SDBS in the root samples in the three parallel experiments was 6.53%, indicating that the method can effectively extract and stably detect SDBS in plant roots.

[0050] (3) Spike recovery experiment To evaluate the quantitative reliability of this method in plant root matrix, SDBS standard solution with a concentration equivalent to that actually measured was added to the bean root sample matrix. Extraction, purification and determination were performed according to the same pretreatment steps as described above, and the spiked recovery rate was calculated. The results are shown in Table 6.

[0051] Table 6 Evaluation of Spiking Recovery and Accuracy of SDBS Quantitative Analysis Method in Plant Root Samples Table 6 shows that, at the above spiking levels, the recoveries of SDBS ranged from 87.53% to 104.29%, with an RSD of 7.91%, indicating that the method has good accuracy and repeatability in complex plant matrices, and the matrix effect is controllable.

[0052] Example 5 Detection of SDBS in water samples from the culture system This embodiment uses a bean hydroponic nutrient solution containing biological backgrounds such as plant secretions as a sample to verify the applicability, accuracy, and precision of the method of the present invention in aquatic substrates.

[0053] (1) Sample pretreatment A certain amount of sodium dodecylbenzenesulfonate (SDBS) was pre-added to the water sample of the common bean culture system to achieve an initial SDBS concentration of 20.0 mg / L. After a certain period of cultivation, the SDBS-exposed hydroponic nutrient solution of the common beans was collected, thoroughly mixed, and 10 mL was transferred to a centrifuge tube and centrifuged at 10,000 r / min for 10 min. The supernatant was then collected. When the SDBS concentration in the sample exceeded the upper limit of the linear range of the calibration curve, it was appropriately diluted with ultrapure water to bring the expected concentration into the linear range of the standard curve before LC-MS / MS determination. The final result was converted according to the dilution factor. The diluted water sample was directly filtered through a 0.22 μm organic filter membrane, and the filtrate was collected in a sample bottle for analysis.

[0054] (2) LC-MS / MS analysis and determination The treated water samples were not purified by SPE and were directly analyzed under the same LC-MS / MS conditions described in Example 2. Quantification was performed using the external standard method. The same sample was measured in triplicate, and the results are shown in Table 7.

[0055] Table 7. Repeatability evaluation of quantitative analysis of SDBS in water samples from the real culture system As shown in Table 7, the average concentration of SDBS in the water sample was 13.63 mg / L, and the relative standard deviation (RSD) was 4.49%, indicating that the method has good repeatability in actual water sample determination.

[0056] (3) Spike recovery experiment The quantitative reliability of the method in actual water samples was evaluated through a spiked recovery experiment. SDBS standard solution was added to water samples with known concentrations to achieve a theoretical spiked concentration increment ΔC = 2.0 mg / L. The samples were then processed and measured using the same procedure, and the spiked recovery rate was calculated. The results are shown in Table 8.

[0057] Table 8 Evaluation of Spike Recovery and Accuracy of SDBS Quantitative Analysis Method in Water Samples of the Culture System Table 8 shows that at a spiking level of 2.0 mg / L, the recovery rate of SDBS ranged from 88.57% to 108.20%, and the relative standard deviation of the spiking results was 3.03%. No obvious matrix interference was observed, indicating that the method has good accuracy in actual water samples.

[0058] The above results demonstrate that the method provided by this invention is not only applicable to the highly selective and sensitive detection of complex solid matrices such as plant tissues, but also, by simplifying the pretreatment steps (filtration or dilution only), is applicable to water samples containing biological organic matter background, showcasing the method's good versatility and reliability.

[0059] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims.

[0060] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for detecting sodium dodecylbenzenesulfonate in plant samples, characterized in that, include: S1. Sample pretreatment: The plant sample is cleaned, freeze-dried, pulverized and sieved to obtain plant sample powder; S2. Extraction: The plant sample powder was subjected to multiple ultrasonic-assisted extractions using a methanol-water mixed solvent, and the extracts were combined and collected. S3. Solid-phase extraction purification: Dilute the combined extract with water, load it onto a weak anion exchange solid-phase extraction column, and then rinse with ammonium acetate buffer solution. After rinsing, elute with an organic solvent containing alkaline components and collect the eluent containing the target analyte. S4. Concentration and Redissolution: The collected eluent was concentrated to near dryness by nitrogen blowing at a temperature not exceeding 45°C, and then redissolved in ultrapure water to a volume of 1.5 mL. The eluent was then filtered through a 0.22 μm microporous membrane to obtain the test solution. S5. Detection: Sodium dodecylbenzenesulfonate in the test solution was qualitatively and quantitatively analyzed using a liquid chromatography-tandem mass spectrometry system. Chromatographic separation was performed using a reversed-phase column, and mass spectrometry detection was performed using an electrospray ionization source in negative ion mode with multiple reaction monitoring for data acquisition. Quantification was performed using the external standard method.

2. The method according to claim 1, characterized in that, In step S2, the volume ratio of methanol to water in the methanol-water mixed solvent is 6-9:1-4.

3. The method according to claim 2, characterized in that, The volume ratio of methanol to water in the methanol-water mixed solvent is 8:

2.

4. The method according to claim 1, characterized in that, The conditions for ultrasonic-assisted extraction in step S2 are as follows: the same sample powder is extracted repeatedly 3 to 5 times, and the extraction time is 10 to 30 minutes each time.

5. The method according to claim 1, characterized in that, The volume fraction of the organic phase in the combined extract after dilution with water in step S3 shall not exceed 20%.

6. The method according to claim 1, characterized in that, The weak anion exchange solid-phase extraction column described in step S3 is activated sequentially with 0.1% ammonia-methanol solution, methanol, and ultrapure water before sample loading.

7. The method according to claim 1, characterized in that, The concentration of the ammonium acetate buffer solution in step S3 is 25 mmol / L and the pH of the solution is 4.

0.

8. The method according to claim 1, characterized in that, The organic solvent containing the alkaline component in step S3 is a 0.1% ammonia-methanol solution.

9. The method according to claim 1, characterized in that, The microporous filter membrane material mentioned in step S4 is polytetrafluoroethylene, nylon, or other materials suitable for aqueous systems.

10. The method according to claim 1, characterized in that, The reversed-phase chromatographic column mentioned in step S5 includes, but is not limited to, a C8 column; the C8 column uses isocratic elution in chromatographic separation, mobile phase A is a 20 mmol / L ammonium formate aqueous solution containing 0.1% formic acid, mobile phase B is acetonitrile, the volume ratio of phase A to phase B is 20:80, the flow rate is 0.2 mL / min, the column temperature is 40℃, and the injection volume is 5 μL; the fragmentation voltage of the mass spectrometry detection is 380V, the collision energy is 35eV, the capillary voltage is 3500V, the gas temperature is 350℃, the gas flow rate is 10 L / min, the nebulizer pressure is 20 psi, and the residence time is 1000 ms.

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