A system and method for simultaneous detection of trace PFAS and antibiotics in water

Abstract

This invention discloses a system and method for the simultaneous detection of trace PFAS and antibiotics in water, in the field of environmental monitoring and analytical chemistry. The system includes a sample pretreatment unit for receiving raw water samples and homogenizing and adjusting their pH. The invention introduces the adjusted water sample, rinsing it sequentially with ammonium acetate-acetic acid buffer solution and ultrapure water, followed by nitrogen drying to reduce interference from metal ions and simultaneously and efficiently remove interfering substances such as humic acid. This allows the solid-phase extraction column to adsorb PFAS and antibiotics. In the eluent concentration unit, the solid-phase extraction column enriched with the target analytes undergoes multi-stage gradient elution. The eluents corresponding to these multi-stage gradient elutions are selectively adapted to PFAS and antibiotics, leading to concentration and volume adjustment to obtain the detection sample, thus achieving the simultaneous detection of both PFAS and antibiotics.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring and analytical chemistry, specifically to a system and method for the simultaneous detection of trace PFAS and antibiotics in water. Background Technology

[0002] Emerging pollutants in the aquatic environment, including persistent organic pollutants (POPs), antibiotics, microplastics, and endocrine disruptors, are becoming a focus of global environmental risk management and continuously challenging the global ecological security barrier. Among them, perfluorinated and polyfluoroalkyl substances (PFAS) have been listed as priority pollutants for control by many countries due to their extreme persistence, bioaccumulation, and health risks (carcinogenicity, immunotoxicity). Meanwhile, antibiotics such as sulfonamides, tetracyclines, and chloramphenicol, due to their overuse leading to environmental residues and triggering chain risks such as the spread of drug resistance genes, are also included in the key monitoring scope. These two types of pollutants often coexist in municipal sewage, industrial wastewater, and agricultural runoff; their combined pollution effects and the challenges of synergistic detection further exacerbate the complexity of environmental risk management.

[0003] PFAS concentrations in surface water are generally at the ng / L level, reaching as high as μg / L around industrial areas. While antibiotic residue concentrations vary significantly depending on the pollution source, they can reach μg / L in water bodies around aquaculture areas, and are often present at the ng / L level in wastewater treatment plant effluent and drinking water sources. The strong stability of the carbon-fluorine bonds in the PFAS molecular structure (bond energy up to 485 kJ / mol) makes them difficult to degrade in the environment and easily accumulates through water, soil, and the food chain. Their amplification effect through the food chain can lead to excessive levels of human serum exposure. Antibiotics, on the other hand, easily accumulate in aquatic organisms, leading to the spread of antibiotic resistance. The potential threat to human health from combined exposure to these two types of pollutants is far greater than that from a single pollutant. Studies have shown that long-term exposure to low concentrations of PFAS may lead to endocrine disorders, immune system damage, and reproductive developmental abnormalities, while the synergistic effect of antibiotic residues and PFAS may exacerbate immunosuppressive effects.

[0004] Traditional water sample testing methods are mostly designed for single pollutants, and have problems such as cumbersome operation, long testing cycle and high cost. They are difficult to meet the needs of rapid and accurate detection when PFAS and antibiotics coexist in complex water samples, and the detection effect is not good. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for the simultaneous detection of trace PFAS and antibiotics in water, in order to solve the problems mentioned above, such as cumbersome operation, long detection cycle, and high cost, which make it difficult to meet the needs of rapid and accurate detection when PFAS and antibiotics coexist in complex water samples.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a system for the simultaneous detection of trace PFAS and antibiotics in water, comprising: The sample pretreatment unit is used to receive the raw water sample and homogenize and adjust the pH to obtain the adjusted water sample. A solid-phase extraction purification unit is connected to a sample pretreatment unit via an injection line. The solid-phase extraction purification unit receives the regulated water sample and introduces a rinsing solution through a rinsing line to adsorb the target analytes and purify the interfering matrix, forming a solid-phase extraction column enriched with the target analytes. The target analytes include PFAS and antibiotics, and the rinsing solution includes ammonium acetate-acetic acid buffer solution and ultrapure water. The eluent concentration unit is connected in series with the solid phase extraction purification unit through the elution pipeline. The eluent concentration unit elutes the target analyte into the eluent through multi-stage gradient elution, and then concentrates and dilutes the eluent with nitrogen to obtain the test sample. An online monitoring unit is connected to the sample pretreatment unit, the solid phase extraction purification unit, and the eluent concentration unit. The online monitoring unit is used to monitor and regulate the pH value of the water sample in the sample pretreatment unit, the flow rate of the fluid in the solid phase extraction purification unit, and the elution process in the eluent concentration unit in real time. The control unit is electrically connected to the sample pretreatment unit and the online monitoring unit. The control unit receives the monitoring signal from the online monitoring unit and is used to adjust the operating parameters of each unit. The liquid chromatography-mass spectrometry (LC-MS) detection unit is connected to the eluent concentration unit. The LC-MS detection unit receives the test sample and performs chromatographic separation and mass spectrometry detection, and outputs quantitative analysis results of PFAS and antibiotics.

[0007] As a further aspect of the present invention: the solid phase extraction purification unit includes a solid phase extraction column, a vacuum negative pressure device, and a high-purity nitrogen source; The solid-phase extraction column is connected to a vacuum negative pressure device and a high-purity nitrogen source, respectively. The solid-phase extraction column is used to adsorb PFAS and antibiotics. The vacuum negative pressure device is used to drive fluid through the solid phase extraction column; The high-purity nitrogen source is used for drying and elution assistance in solid-phase extraction columns.

[0008] As a further aspect of the present invention: the eluent concentration unit includes a gradient elution module, a nitrogen blowing concentration module, and a volume-fixing module connected in sequence. The gradient elution module sequentially delivers methanol, a methanol-water mixture, and an ammonia-methanol mixture as eluents via pipelines. The nitrogen blowing concentration module receives the combined eluent and concentrates the eluent containing the target analyte by purging with gentle nitrogen gas through a pipeline to obtain a concentrated sample. The volume adjustment module uses a pipeline to adjust the volume of the concentrated sample using a methanol-water mixture. The pipelines of the gradient elution module, the nitrogen blowing concentration module, and the volume control module are interwoven to achieve integrated elution-concentration-volume control operation.

[0009] As a further aspect of the present invention: the online monitoring unit includes a pH sensor, a flow rate controller, and a timing module; The pH sensor is embedded inside the sample pretreatment unit. The pH sensor is used to detect the pH value of the water sample in the sample pretreatment unit and generate an acid-base electrical signal. The flow rate controller is integrated into the sample inlet line, rinsing line, and elution line of the eluent concentration unit of the solid phase extraction purification unit. The flow rate controller is used for fluid flow rate control and generates a flow rate electrical signal. The acid-base electrical signal and the flow velocity electrical signal form a monitoring signal; The timing module is electrically connected to the flow rate controller. The timing module is used to control the opening and closing of the flow rate controller at regular intervals to control the flow rate of the fluid in the solid phase extraction purification unit and the elution process in the eluent concentration unit. The timing module is also used to automatically adjust the nitrogen purging intensity and vacuum negative pressure parameters.

[0010] As a further aspect of the present invention: the sample pretreatment unit includes an acid-base module, which is used to provide an acidic solution and an alkaline solution; The control unit receives acid-base electrical signals and flow rate electrical signals. The control unit is electrically connected to the acid-base module. The control unit controls the acid-base module to output acidic or alkaline solutions according to the acid-base electrical signals, so as to adjust the pH of the water sample in the sample pretreatment unit. The control unit controls the flow rate controller in real time based on the flow rate electrical signal to control the flow rate of the fluid.

[0011] Secondly, the present invention provides a method for simultaneous detection of trace PFAS and antibiotics in water, the method comprising: S1: Input the water sample containing the target substance into the sample pretreatment unit, and control the homogenization and pH adjustment through the control unit. After adjusting to the target pH range, it is delivered to the solid phase extraction purification unit. The target substances include PFAS and antibiotics. S2: Start the solid phase extraction purification unit and control the flow of the adjusted water sample and eluent through the activated solid phase extraction column via the online monitoring unit, so that the target substance is effectively adsorbed and the interfering matrix is ​​discharged, to ensure that the target substance is fully adsorbed and the interfering matrix is ​​removed. S3: Start the eluent concentration unit and control the linkage gradient elution through the online monitoring unit. Methanol, methanol-water mixture and ammonia-methanol mixture are sequentially input into the solid phase extraction column as eluents. The eluted liquid is collected, concentrated by nitrogen blowing and then brought to a fixed volume to obtain the test sample, so as to achieve graded gradient elution of the target analyte. S4: The sample enters the liquid chromatography-mass spectrometry (LC-MS) unit, where it is separated by chromatography and detected by mass spectrometry to output quantitative results.

[0012] As a further aspect of the present invention: in step S1, pH adjustment is performed using an acetic acid solution and an ammonia solution, and the target pH range is pH 5.0-pH 7.0; The activation process involves sequentially passing an ammonia-methanol mixture, methanol, and ultrapure water through the solid-phase extraction column at a flow rate of 1 mL / min to 3 mL / min to thoroughly clean and activate the column.

[0013] As a further aspect of the present invention: in step S2, the loading flow rate of the adjusted water sample is 4 mL / min-6 mL / min, and the rinsing fluid is successively ammonium acetate-acetic acid buffer solution and ultrapure water, with a rinsing flow rate of 1 mL / min-3 mL / min.

[0014] As a further aspect of the present invention: the graded gradient elution includes: The isocratic elution was performed sequentially with pure methanol as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. The isocratic elution was used to capture weakly polar antibiotics. Eluting was performed using a slow slope with a methanol-water mixture containing 5 mM ammonium acetate as the eluent, at a flow rate of 1.0 mL / min to 2.0 mL / min. This slow slope elution was used to balance the ionic binding force and solubility of PFAS. Strong elution was performed using an ammonia-methanol mixture as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. This strong elution was used to create an alkaline environment and break the strong ionic bonds between PFAS and the column. The rinsing and elution process uses an ammonia-methanol mixture as the rinsing solution at a flow rate of 1.0 mL / min to 3.0 mL / min. This rinsing and elution is used for impurity removal and activity regeneration of the solid-phase extraction column. The eluents corresponding to isocratic elution, gentle slope elution, and strong elution were collected, concentrated by nitrogen blowing, and then brought to a fixed volume to obtain the test sample.

[0015] As a further aspect of the present invention: the eluent of isocratic elution has a methanol mass fraction of 100%, and the flow rate of pure methanol as the eluent is 1.5 mL / min; The eluent for the gentle slope elution contains a methanol solution with 5 mM ammonium acetate in a volume ratio of 2:98 to a pure aqueous solution, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the eluent for strong elution is 1:199, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the rinsing solution is 1:99, and the rinsing flow rate is 2.0 mL / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, after introducing the conditioned water sample, it is sequentially rinsed with ammonium acetate-acetic acid buffer solution and ultrapure water, and then dried with nitrogen gas. This reduces the interference of metal ions in the conditioned water sample and simultaneously and efficiently removes interfering substances such as humic acid. Combined with nitrogen purging to eliminate residual moisture, the solid-phase extraction column adsorbs PFAS and antibiotics. In the eluent concentration unit, the solid-phase extraction column enriched with target substances undergoes multi-stage gradient elution. The eluents corresponding to the multi-stage gradient elution are differentially adapted to PFAS and antibiotics, retaining the characteristics of PFAS and antibiotics. Then, the sample is concentrated and brought to a fixed volume to obtain the test sample. The liquid chromatography-mass spectrometry (LC-MS) detection unit detects PFAS and antibiotics in the test sample to obtain quantitative analysis results of PFAS and antibiotics. This achieves simultaneous detection of dual contaminants, PFAS and antibiotics, reduces the detection cycle, and effectively reduces detection costs.

[0017] 2. In this invention, multi-stage gradient elution is achieved through an eluent concentration unit, resulting in a stepwise increase in elution intensity. Targeted isocratic elution preferentially dissociates the hydrophobic interaction between weakly polar antibiotics and the packing material. Then, a gentle slope elution balances the ionic binding force and solubility of short-chain PFAS. Finally, a steeply increasing strong elution stage utilizes an alkaline environment to disrupt the strong ionic bonds of long-chain PFAS, completely stripping long-chain PFAS from polar antibiotics. This achieves the orderly release of different types of target substances, completely avoiding the problem of target substance mixing in traditional elution. It also creates a clear boundary between the elution processes of various antibiotics and PFAS, achieving highly efficient enrichment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system connection structure of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention.

[0019] In the diagram: 1. Sample pretreatment unit; 2. Solid phase extraction and purification unit; 3. Eluent concentration unit; 4. Online monitoring unit; 5. Control unit; 6. Liquid chromatography-mass spectrometry (LC-MS) detection unit. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example:

[0022] Liquid-liquid extraction (LLE), a traditional pretreatment method extending the national standard HJ 834-2017 (primarily targeting semi-volatile organic compounds in soil and sediments) to water pollutant analysis, is facing a triple challenge in terms of efficiency, reliability, and synergistic enrichment capabilities: a single extraction (including multiple extractions) requires more than 200 mL of dichloromethane. Based on processing 1000 samples annually, the solvent cost alone reaches $6000-10000 (including losses), and the total cost, including labor and glassware, can reach $15000. A single operation takes more than 4 hours (including shaking, layering, separation, and concentration), making it difficult to meet high-throughput detection requirements. More importantly, its enrichment mechanism, which relies on hydrophobic partitioning, has inherent flaws: highly polar sulfonamide antibiotics have difficulty entering the organic phase, resulting in recovery rates often below 50%; while short-chain PFAS, although slightly more hydrophobic, easily form hydrogen bonds with water molecules in actual water samples, similarly limiting extraction efficiency (recovery rate 30%-60%). More seriously, if the concentration of humic acid in the actual water sample is >10 mg / L or contains surfactants, it can easily trigger a severe emulsification effect, leading to significant fluctuations in the extraction yield of both target substances. The relative standard deviation (RSD) of the recovery rate is often >15%, severely weakening data reproducibility and making it impossible to achieve simultaneous and efficient enrichment of PFAS and antibiotics. Although hybrid SPE modes (such as WAX, weak anion exchange-reverse composite mechanism) attempt to balance selectivity and versatility through dual action to improve the adsorption effect of single pollutants, they have significant drawbacks in the scenario of synergistic enrichment of two types of substances: First, the activation and rinsing processes lack systematic optimization, and metal ions in the water (such as Ca2+, Mg2+) easily form complexes with PFAS, and may also undergo coordination reactions with the carboxyl and amino groups of antibiotics, resulting in the simultaneous loss of both target substances; Second, large molecular organic matter such as humic acid easily occupies adsorption sites. Firstly, the recovery rates of both PFAS and antibiotics in actual water samples fluctuate significantly (relative standard deviation RSD > 15%). Secondly, in traditional static extraction mode, the contact efficiency between the solvent and the packing material is low, requiring multiple repeated operations to increase the enrichment factor, resulting in pretreatment time exceeding 3 hours. Furthermore, it is difficult to achieve simultaneous and efficient elution of both substances using a single elution condition—strongly alkaline eluents, while beneficial for PFAS desorption, easily lead to the degradation of tetracycline antibiotics; weakly acidic eluents inhibit the ion exchange of antibiotics, resulting in low recovery rates. At the instrumental analysis level, the sensitivity, matrix interference resistance, and synergistic detection adaptability of liquid chromatography-tandem mass spectrometry (LC-MS / MS) technology still need improvement. From the perspective of separation characteristics, short-chain PFAS, due to their strong polarity and short retention time, tend to exhibit peak broadening (symmetry factor < 0.8) on conventional C18 columns. In contrast, tetracycline antibiotics, due to the presence of multiple hydroxyl and amino groups in their molecular structure, readily react with residual silanol groups on the column to produce tailing (symmetry factor > 1.5). The retention behaviors of the two types of substances differ significantly, making it difficult to achieve effective separation using a single chromatographic condition.From the perspective of ionization efficiency, an unreasonable configuration of buffer salt concentration and organic phase ratio in the mobile phase system can lead to a decrease in the ionization efficiency of the target analyte within the ion source: while a high concentration of buffer salt is beneficial for the negative ionization of PFAS, it will inhibit the positive ionization signal of tetracycline antibiotics; an excessively high proportion of organic phase will shorten the PFAS retention time and exacerbate matrix interference. Especially in complex matrices (such as industrial wastewater and aquaculture wastewater), the matrix effect can cause the signal inhibition rate of both types of substances to be as high as 40% or more, and the ionization competition between antibiotics and PFAS will further reduce the detection sensitivity.

[0023] To address the challenges of detecting PFAS and antibiotics coexisting in complex water samples: on the one hand, the strong polarity and acidity of PFAS lead to insufficient adsorption capacity of traditional SPEs, resulting in low recovery rates of short-chain PFAS (such as PFBA); on the other hand, typical antibiotics such as sulfonamides and tetracyclines, due to their large polarity differences and easy degradation, conflict with the adsorption / elution conditions required by PFAS. Existing methods struggle to achieve the same enrichment effect for both, often resulting in low antibiotic recovery rates or incomplete PFAS desorption.

[0024] Please see Figure 1 In this embodiment of the invention, a system for simultaneous detection of trace PFAS and antibiotics in water includes: The sample pretreatment unit 1 is used to receive the original water sample and perform homogenization and pH adjustment to obtain the adjusted water sample. The acid-base module in the sample pretreatment unit 1 provides acidic and alkaline solutions. The acidic solution is acetic acid solution and the alkaline solution is ammonia solution. The acid-base module includes a pump with high-precision flow control. The pump is used for precise supply of acidic and alkaline solutions. The sample pretreatment unit 1 has a built-in vortex mixer. After adjusting the pH of the original water sample, the internal fluid is homogenized through the vortex mixer to ensure the homogeneity of the water sample. The pump and vortex mixer are connected to the control unit 5. The online monitoring unit 4 first detects the pH value of the original water sample. When the original water sample does not match the preset pH range, the control unit 5 controls the pump to adaptively introduce the corresponding volume of acetic acid solution or ammonia solution according to the detected pH value of the original water sample, so that the adjusted water sample meets the preset pH range. The internal fluid is then homogenized through the vortex mixer to form the adjusted water sample. Solid-phase extraction purification unit 2 is connected to sample pretreatment unit 1 via an injection line. Solid-phase extraction purification unit 2 receives the regulated water sample and introduces eluent through an elution line for target adsorption and interfering matrix purification, forming a solid-phase extraction column enriched with target substances. The target substances include PFAS and antibiotics. The eluent includes ammonium acetate-acetic acid buffer solution and ultrapure water. Solid-phase extraction purification unit 2 includes a solid-phase extraction column. The inlet end of the solid-phase extraction column is connected to the outlet end of sample pretreatment unit 1 via an injection line. The solid-phase extraction column is also connected to a vacuum negative pressure device and a high-purity nitrogen source. The vacuum negative pressure device forms a negative pressure end at one end of the solid-phase extraction column to provide a power source for the fluid flow inside the solid-phase extraction column. The solid-phase extraction column is connected to an elution device via an elution line, and the elution device supplies eluent. Furthermore, the solid-phase extraction column is Waters Oasis WAX, Waters Oasis HLB, or other hydrophilic-lipophilic balanced solid-phase extraction column, the packing material of the solid-phase extraction column is a weak anion exchange adsorbent, and the nitrogen source has a nitrogen purity of 99.999%.

[0025] The eluent concentration unit 3 is connected in series with the solid phase extraction purification unit 2 through the elution pipeline. The eluent concentration unit 3 elutes the target substance into the eluent through multi-stage gradient elution, and concentrates and adjusts the volume of the eluent with nitrogen blowing to obtain the test sample. The eluent concentration unit 3 is equipped with a mild nitrogen purging device, which is used to adjust the nitrogen purging temperature. Online monitoring unit 4 is connected to sample pretreatment unit 1, solid phase extraction purification unit 2 and eluent concentration unit 3. Online monitoring unit 4 is used to monitor and regulate the pH value of the water sample in sample pretreatment unit 1, the flow rate of the fluid in solid phase extraction purification unit 2 and the elution process in eluent concentration unit 3 in real time. Control unit 5 is electrically connected to sample pretreatment unit 1 and online monitoring unit 4. Control unit 5 receives monitoring signals from online monitoring unit 4 and is used to adjust the operating parameters of each unit. Control unit 5 adjusts the pH value of the water sample in sample pretreatment unit 1 according to the monitoring signals. The liquid chromatography-mass spectrometry (LC-MS) detection unit 6 is connected to the eluent concentration unit 3. The LC-MS detection unit 6 receives the test sample and performs chromatographic separation and mass spectrometry detection, and outputs the quantitative analysis results of PFAS and antibiotics.

[0026] Specifically, this system uses sample pretreatment unit 1 to adjust the pH of the original water sample and homogenize it, ensuring the adjusted water sample remains within a set pH range. This is suitable for PFAS anionization and antibiotic zwitterion stabilization. During the activation and rinsing process in solid-phase extraction purification unit 2, after the adjusted water sample is introduced, it is sequentially rinsed with ammonium acetate-acetic acid buffer solution and ultrapure water, and then dried with nitrogen gas to reduce interference from metal ions in the adjusted water sample. This simultaneously and efficiently removes interfering substances such as humic acid. Combined with nitrogen purging to eliminate residual moisture, this allows the solid-phase extraction column to effectively remove interference. PFAS and antibiotics are adsorbed, and the solid-phase extraction column enriched with the target analytes is subjected to multi-stage gradient elution in the eluent concentration unit 3. The eluents corresponding to the multi-stage gradient elution are adapted to PFAS and antibiotics to retain the characteristics of PFAS and antibiotics. Then, the sample is concentrated and brought to a fixed volume to obtain the test sample. The liquid chromatography-mass spectrometry (LC-MS) detection unit 6 detects PFAS and antibiotics in the test sample to obtain quantitative analysis results of PFAS and antibiotics, realizing the simultaneous detection of dual pollutants of PFAS and antibiotics, reducing the detection cycle and effectively reducing the detection cost. Furthermore, the eluent concentration unit 3 achieves multi-stage gradient elution, realizing a stepwise increase in elution intensity. Through targeted isocratic elution, it preferentially dissociates the hydrophobic interaction between weakly polar antibiotics and packing material. Then, through gentle slope elution, it balances the ionic binding force and solubility of short-chain PFAS. Finally, through a steeply rising strong elution stage, it uses an alkaline environment to break the strong ionic bonds of long-chain PFAS, completely stripping long-chain PFAS from polar antibiotics. This achieves the orderly release of different types of target substances, completely avoiding the problem of target substance mixing in traditional elution. It also creates a clear boundary between the elution processes of various antibiotics and PFAS, achieving highly efficient enrichment. Furthermore, the control unit 5 intelligently controls and interacts with the sample pretreatment unit 1, solid-phase extraction purification unit 2, eluent concentration unit 3, and liquid chromatography-mass spectrometry (LC-MS) detection unit 6. Based on the preset detection process and parameters, the operating status of each unit is precisely adjusted to control the pH adjustment accuracy of the sample pretreatment unit 1, the rinsing time and nitrogen drying degree of the solid-phase extraction purification unit, the gradient elution parameters of the eluent concentration unit 3, and the detection conditions of the LC-MS detection unit, ensuring the stable and efficient operation of the entire detection system and improving the accuracy and repeatability of the detection.

[0027] Preferably, the solid-phase extraction purification unit 2 includes a solid-phase extraction column, a vacuum negative pressure device, and a high-purity nitrogen source; The solid-phase extraction column is connected to a vacuum negative pressure device and a high-purity nitrogen source, respectively. The solid-phase extraction column is used to adsorb PFAS and antibiotics. A vacuum negative pressure device is used to drive fluid through a solid-phase extraction column; A high-purity nitrogen source is used for drying and elution assistance in the solid-phase extraction column. The adjusted water sample flows through the solid-phase extraction column from top to bottom, while the eluent flows through the solid-phase extraction column from bottom to top or from top to bottom, achieving bidirectional flow of adsorption and elution of the target analyte.

[0028] Specifically, in the adsorption stage of the solid-phase extraction purification unit 2, the regulated water sample flows from top to bottom through the solid-phase extraction column under the drive of the vacuum negative pressure device, and the target analyte is effectively adsorbed in the column. In the elution stage, by controlling the flow direction of the eluent, it can flow from bottom to top or from top to bottom through the solid-phase extraction column to achieve complete elution of the target analyte. At the same time, the introduction of a high-purity nitrogen source can not only be used for drying the solid-phase extraction column, but also provide assistance in the elution process, further improving the elution efficiency. The bidirectional flow design of adsorption-elution greatly enhances the enrichment capacity of the solid-phase extraction purification unit 2 for the target analyte.

[0029] Preferably, the eluent concentration unit 3 includes a gradient elution module, a nitrogen blowing concentration module, and a volume adjustment module connected in sequence. The gradient elution module sequentially delivers methanol, a methanol-water mixture, and an ammonia-methanol mixture as eluents via pipelines. The nitrogen blowing concentration module receives the combined eluent and concentrates the eluent containing the target analyte by purging with gentle nitrogen gas through a pipeline to obtain a concentrated sample. The volume adjustment module uses a pipeline to adjust the volume of the concentrated sample with a methanol-water mixture, using a polypropylene centrifuge tube (15 mL) as the volume adjustment container. The pipelines of the gradient elution module, the nitrogen blowing concentration module, and the volume control module are interwoven to achieve integrated elution-concentration-volume control operation.

[0030] Specifically, the gradient elution module is suitable for different eluents and their elution capabilities and efficiencies on target analytes. By precisely controlling the delivery sequence and ratio of methanol, methanol-water mixture, and ammonia-methanol mixture, it achieves effective and thorough elution of target analytes adsorbed on the solid-phase extraction column. The nitrogen purging module uses a gentle nitrogen purging method to avoid potential damage to target analytes caused by high temperatures, while ensuring that the solvent in the eluent can be removed quickly and effectively, thereby obtaining a high concentration of target analyte sample. The volume adjustment module adds an appropriate amount of methanol-water mixture to adjust the volume of the concentrated sample to a certain level, facilitating subsequent detection and analysis. Polypropylene centrifuge tubes are used as volume adjustment containers, which ensures sample stability and facilitates operation and storage.

[0031] Preferably, the online monitoring unit 4 includes a pH sensor, a flow rate controller, and a timing module. Further, the pH sensor has a measurement range of 0-14 and an accuracy of ±0.01, and the flow rate controller has an adjustment range of 0.1-10 mL / min. The pH sensor is embedded inside the sample pretreatment unit 1. The pH sensor is used to detect the pH value of the water sample in the sample pretreatment unit 1 and generate an acid-base electrical signal. The flow rate controller is integrated into the sample inlet line, rinsing line of the solid phase extraction purification unit 2 and the elution line of the eluent concentration unit 3. The flow rate controller is used for fluid flow rate control and generates flow rate electrical signals. Acid-base electrical signals and flow velocity electrical signals form monitoring signals; The timing module is electrically connected to the flow rate controller. The timing module is used to control the opening and closing of the flow rate controller at timed intervals, so as to control the flow rate of the fluid in the solid phase extraction purification unit 2 and the elution process of the eluent concentration unit 3. The timing module is also used to automatically adjust the nitrogen purging intensity and vacuum negative pressure parameters.

[0032] Specifically, the timing module has a high-precision timing function, which can accurately control the operating time interval of each unit according to the preset program, ensuring that the solid phase extraction purification unit 2 completes the adsorption-desorption cycle in the optimal time window, while enabling the eluent concentration unit 3 to achieve gradient concentration under the preset vacuum degree.

[0033] Preferably, the sample pretreatment unit 1 includes an acid-base module for providing acidic and alkaline solutions; Control unit 5 receives acid-base electrical signals and flow rate electrical signals. Control unit 5 is electrically connected to the acid-base module. Control unit 5 controls the acid-base module to output acidic or alkaline solutions according to the acid-base electrical signals, so as to adjust the pH of the water sample in sample pretreatment unit 1. The control unit 5 controls the flow rate controller in real time based on the flow rate electrical signal to control the flow rate of the fluid.

[0034] Specifically, the built-in intelligent algorithm of the control unit 5 can quickly analyze acid and alkali electrical signals, determine the deviation between the current pH value of the water sample and the target pH value, and then accurately control the acid and alkali module to output the corresponding amount of acidic or alkaline solution to ensure that the pH value of the water sample quickly and stably reaches the preset range.

[0035] Please see Figure 2 In this embodiment of the invention, a method for simultaneous detection of trace PFAS and antibiotics in water includes: S1: Input the water sample containing the target substance into the sample pretreatment unit 1. The homogenization and pH adjustment are controlled by the control unit 5. After adjusting to the target pH range, the sample is sent to the solid phase extraction purification unit 2. The target substances include PFAS and antibiotics. The specific steps are as follows: Start the sample pretreatment unit 1 to homogenize the sample. After filtering the water sample containing the target analyte, adjust the pH to 6.0-8.0 with acid or alkaline solution. At the same time, activate the solid phase extraction column. Pass the weak anion exchange column sequentially with ammonia-methanol mixed solution, methanol and ultrapure water at a flow rate of 1-3 mL / min (marked as the first flow rate). During the activation process, control the flow rate to keep the packing material moist. S2: Start the solid phase extraction purification unit 2 and control the flow of the regulated water sample and eluent through the activated solid phase extraction column via the online monitoring unit 4 to ensure that the target substance is effectively adsorbed and the interfering matrix is ​​discharged. This ensures that the target substance is fully adsorbed and the interfering matrix is ​​removed. The eluent includes ammonium acetate-acetic acid buffer solution and ultrapure water. Specifically, the regulated water sample is passed through the activated solid phase extraction column at a flow rate of 4 mL / min-6 mL / min, and the solid phase extraction column is rinsed sequentially with ammonium acetate-acetic acid buffer solution and ultrapure water at a flow rate of 1 mL / min-3 mL / min. Then, nitrogen blowing is performed for drying. The flow rate parameters of the fluids are controlled and adjusted by the flow rate controller of the online monitoring unit 4. The specific steps are as follows: After column activation, the solid phase extraction purification unit 2 is started, and the flow rate is controlled by the online monitoring unit 4 to ensure that the target analyte is fully adsorbed and the interfering matrix is ​​removed. The pretreated water sample is passed through the activated solid phase extraction column at a flow rate of 4 mL / min-6 mL / min (marked as the second flow rate). The solid phase extraction column is then rinsed with ammonium acetate-acetic acid buffer solution and ultrapure water at a flow rate of 1 mL / min-3 mL / min (marked as the third flow rate). Subsequently, nitrogen blowing is performed for drying. The flow rate parameters are set by the online monitoring unit 4. S3: Start the eluent concentration unit 3 and control the linkage gradient elution through the online monitoring unit 4. Methanol, methanol-water mixture and ammonia-methanol mixture are sequentially input into the solid phase extraction column as eluents. The eluted liquid is collected, concentrated by nitrogen blowing and then brought to a fixed volume to obtain the test sample, so as to achieve graded gradient elution of the target analyte. The specific steps are as follows: The eluent concentration unit 3 is started, and simultaneously, the online monitoring unit 4 presets a gradient elution program linked to "flow rate-solvent-time" to achieve efficient fractional elution of antibiotics and PFAS. The gradient elution proceeds sequentially according to the logic of "targeted dissociation → synergistic desorption → potent stripping → column regeneration." Core parameters and operational details are interconnected: The first stage uses a targeted isocratic elution mode to specifically capture weakly polar antibiotics. Chromatographically pure methanol filtered through a 0.22 μm filter membrane is used as the eluent, with a flow rate set at 1.0 mL / min-2.0 mL / min. The isocratic elution mode is maintained throughout, utilizing the hydrophobic effect of methanol to precisely dissociate the antibiotics from the column packing material while preventing premature elution of short-chain PFAS. After completion, the process switches to the second stage, using a gentle slope gradient elution mode to simultaneously recover residual antibiotics and short-chain PFAS. The eluent is a methanol-water mixture containing 5 mM ammonium acetate, with a flow rate maintained at 1.0-2.0 mL / min. The flow rate remains consistent with the previous stage. The low organic phase and gentle slope system balance the ionic binding force and solubility of PFAS. The third stage then employs a steep-elution mode to thoroughly remove long-chain PFAS and polar antibiotics. An ammonia-methanol mixture is used as the eluent, and the flow rate is controlled at 1.0 mL / min–2.0 mL / min. The alkaline environment created by ammonia breaks the strong ionic bonds between PFAS and the column, achieving steep-elution efficiency. After the main gradient elution process, the fourth stage, a fast-rinse regeneration elution mode, is initiated to remove column impurities and regenerate activity. An ammonia-methanol mixture is used as the washing solution, with a flow rate of 1.0 mL / min–3.0 mL / min. The eluent in this stage is directly discharged into the waste container to avoid cross-contamination with the target analyte. The first to third gradient eluents are combined and collected in brown centrifuge tubes to prevent photodegradation of the target analyte. The collected eluent is then transferred to a nitrogen evaporator, with the temperature set at 30 °C–40 °C. At ℃ and a nitrogen flow rate of 4-6 mL / min, concentrate to near dryness, i.e., the remaining liquid in the solution is about 0.5 mL. To avoid complete evaporation and loss of the target substance, concentrate and dry all the eluent, and then make up to volume with a methanol-water mixture (volume ratio 1:2-2:1). S4: The sample enters the liquid chromatography-mass spectrometry (LC-MS) detection unit 6, and the quantitative results are output through chromatographic separation and mass spectrometry detection. The specific steps are as follows: Start the LC-MS detection unit 6 and follow the procedure of "instrument warm-up - system equilibration - gradient elution - mass spectrometry detection" to ensure efficient separation and accurate response of the target analyte. First, perform instrument warm-up and system equilibration. Turn on the ultra-high performance liquid chromatography (UPLC) and triple quadrupole mass spectrometry (MS / MS). Set the solid phase extraction column temperature to 30℃-40℃ and the mass spectrometry ion source temperature to 320℃-380℃. After warming for 20-40 minutes, wash the column with the initial mobile phase ratio (Phase A: 5-10mM ammonium acetate aqueous solution, pH 4.5-5.0; Phase B: methanol containing 5-10mM ammonium acetate, A:B = 70:30-80:20) until the baseline is stable. After system equilibration, start the autosampler and take 1-10 ml of the sample to a fixed volume. μL was injected into the column, and gradient elution was used (0-2 min to maintain phase A at 70%-80%, 2-10 min was the "slow gradient" stage to solve the problem of peak overlap between sulfonamides and medium-chain PFAS in traditional fast gradients, phase A decreased linearly from 70%-80% to 20%-40%, 10-18 min was the "fast gradient" stage to avoid excessive elution time for long-chain components, phase A decreased linearly from 20%-40% to 5%-15%, 18-22 min was maintained at 5%-15%, and 22-25 min was restored to the initial ratio). The mobile phase flow rate was controlled at 0.3-0.4 mL / min. Mass spectrometry detection was performed in multiple reaction monitoring (MRM) mode. PFAS, sulfonamides and chloramphenicol were detected in negative ion mode, and tetracyclines were detected in positive ion mode. Through the linkage program of UPLC and MS / MS, the ionization mode and ion pair detection parameters are automatically switched at different stages of gradient elution. ESI- and ESI+ dual-mode monitoring are started simultaneously from 2 to 10 min (elution stage of sulfonamides and medium-chain PFAS), and the signal acquisition of the corresponding ion pairs is enhanced from 10 to 18 min (elution stage of long-chain PFAS and tetracyclines), so as to ensure that all kinds of targets obtain the best detection sensitivity and qualitative accuracy. Furthermore, the solid phase extraction column temperature is 35 ℃, the mass spectrometry ion source temperature is customized according to different ion modes, the negative ion mode temperature is 350 ℃, the positive ion mode temperature is 330 ℃, and the instrument warm-up time is 30 minutes. Furthermore, the initial mobile phase consisted of phase A and phase B. Phase A was a 5 mM ammonium acetate aqueous solution at pH 4.8, and phase B was methanol containing 5 mM ammonium acetate. The initial mobile phase ratio A:B was 70:30, the injection volume was 1 μL, and the mobile phase flow rate was 0.35 mL / min. Furthermore, the gradient elution mode is as follows: 0-2 min maintains 70% of phase A, 2-10 min linearly reduces phase A from 70% to 35%, 10-18 min linearly reduces phase A from 35% to 5%, 18-22 min maintains phase A at 5%, and 22-25 min restores to the initial mobile phase ratio.

[0036] This method balances adsorption efficiency and purification effect by controlling the flow rate in stages from 2 mL / min during sample loading to 5 mL / min during elution. It is combined with two-stage synergistic elution, namely methanol pre-washing to remove impurities and ammonia-methanol simultaneous elution of two types of target substances. This shortens the single-sample synergistic pretreatment time and enables simultaneous high-throughput detection of PFAS and antibiotics without the need for complex equipment, thereby improving detection efficiency. This method overcomes the bottlenecks of poor solvent compatibility and limited contaminant coverage of traditional methods. It adopts a methanol-water volume adjustment scheme, which perfectly matches the reversed-phase chromatography-mass spectrometry system and eliminates the solvent effect between the two types of substances. This method shows good applicability to different matrices (such as surface water, groundwater, and industrial wastewater), effectively solving the problems of low detection sensitivity and poor selectivity of traditional methods in complex matrices, and significantly improving the universality and accuracy of detection.

[0037] Preferably, in step S2, pH adjustment is performed using an acetic acid solution and an ammonia solution, with a target pH range of pH 5.0-pH 7.0. The activation process involves sequentially passing an ammonia-methanol mixture, methanol, and ultrapure water through the solid-phase extraction column at a flow rate of 1 mL / min to 3 mL / min to thoroughly clean and activate the column.

[0038] Preferably, in step S2, the loading flow rate of the adjusted water sample is 4 mL / min-6 mL / min, and the rinsing fluid is successively ammonium acetate-acetic acid buffer solution and ultrapure water, with a rinsing flow rate of 1 mL / min-3 mL / min.

[0039] Preferably, graded gradient elution includes: Isocratic elution was performed sequentially using pure methanol as the eluent at a flow rate of 1.0 mL / min–2.0 mL / min. Isocratic elution was used to capture weakly polar antibiotics. Eluting was performed using a slow slope with a methanol-water mixture containing 5 mM ammonium acetate as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. The slow slope elution was used to balance the ionic binding force and solubility of PFAS. Strong elution was performed using an ammonia-methanol mixture as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. This strong elution was used to create an alkaline environment and break the strong ionic bonds between PFAS and the column. The rinsing and elution were performed using an ammonia-methanol mixture as the rinsing solution at a flow rate of 1.0 mL / min to 3.0 mL / min. This rinsing and elution was used for impurity removal and activity regeneration of the solid-phase extraction column. The eluents corresponding to isocratic elution, gentle slope elution, and strong elution were collected, concentrated by nitrogen blowing, and then brought to a fixed volume to obtain the test sample.

[0040] Preferably, the eluent for isocratic elution contains 100% methanol by mass, and the flow rate of pure methanol as the eluent is 1.5 mL / min. The eluent for gentle slope elution contains a methanol solution with 5 mM ammonium acetate in a volume ratio of 2:98 to a pure aqueous solution, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the eluent for strong elution is 1:199, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the rinsing solution was 1:99, and the rinsing flow rate was 2.0 mL / min.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A system for simultaneous detection of trace PFAS and antibiotics in water, characterized in that, include: The sample pretreatment unit (1) is used to receive the original water sample and homogenize and adjust the pH to obtain the adjusted water sample. Solid phase extraction purification unit (2), the solid phase extraction purification unit (2) is connected to sample pretreatment unit (1) through sample injection pipeline, the solid phase extraction purification unit (2) receives the adjusted water sample and introduces the eluent through the rinsing pipeline for target adsorption and interfering matrix purification, forming a solid phase extraction column enriched with target substances, wherein the target substances include PFAS and antibiotics, and the eluent includes ammonium acetate-acetic acid buffer solution and ultrapure water; The eluent concentration unit (3) is connected in series with the solid phase extraction purification unit (2) through the elution pipeline. The eluent concentration unit (3) elutes the target substance into the eluent through multi-stage gradient elution, and concentrates and dilutes the eluent with nitrogen to obtain the test sample. Online monitoring unit (4), which is connected to sample pretreatment unit (1), solid phase extraction purification unit (2) and eluent concentration unit (3), is used to monitor and regulate the pH value of water sample in sample pretreatment unit (1), the flow rate of fluid in solid phase extraction purification unit (2) and the elution process of eluent concentration unit (3) in real time. Control unit (5), which is electrically connected to sample pretreatment unit (1) and online monitoring unit (4), receives monitoring signals from online monitoring unit (4) and is used to adjust the operating parameters of each unit; The liquid chromatography-mass spectrometry (LC-MS) detection unit (6) is connected to the eluent concentration unit (3) and electrically connected to the control unit (5). The LC-MS detection unit (6) receives the test sample and performs chromatographic separation and mass spectrometry detection, and outputs the quantitative analysis results of PFAS and antibiotics.

2. The system for simultaneous detection of trace PFAS and antibiotics in water according to claim 1, characterized in that: The solid-phase extraction purification unit (2) includes a solid-phase extraction column, a vacuum negative pressure device and a high-purity nitrogen source; The solid-phase extraction column is connected to a vacuum negative pressure device and a high-purity nitrogen source, respectively. The solid-phase extraction column is used to adsorb PFAS and antibiotics. The vacuum negative pressure device is used to drive fluid through the solid phase extraction column; The high-purity nitrogen source is used for drying and elution assistance in solid-phase extraction columns.

3. The system for simultaneous detection of trace PFAS and antibiotics in water according to claim 2, characterized in that: The eluent concentration unit (3) includes a gradient elution module, a nitrogen blowing concentration module, and a volume-fixing module connected in sequence: The gradient elution module sequentially delivers methanol, a methanol-water mixture, and an ammonia-methanol mixture as eluents via pipelines. The nitrogen blowing concentration module receives the combined eluent and concentrates the eluent containing the target analyte by purging with gentle nitrogen gas through a pipeline to obtain a concentrated sample. The volume adjustment module uses a pipeline to adjust the volume of the concentrated sample using a methanol-water mixture. The pipelines of the gradient elution module, the nitrogen blowing concentration module, and the volume control module are interwoven to achieve integrated elution-concentration-volume control operation.

4. The system for simultaneous detection of trace PFAS and antibiotics in water according to claim 3, characterized in that: The online monitoring unit (4) includes a pH sensor, a flow rate controller, and a timing module; The pH sensor is embedded inside the sample pretreatment unit (1). The pH sensor is used to detect the pH value of the water sample in the sample pretreatment unit (1) and generate an acid-base electrical signal. The flow rate controller is integrated into the sample inlet line, rinsing line and elution line of the solid phase extraction purification unit (2) and the eluent concentration unit (3). The flow rate controller is used for fluid flow rate control and generates flow rate electrical signals. The acid-base electrical signal and the flow velocity electrical signal form a monitoring signal; The timing module is electrically connected to the flow rate controller. The timing module is used to control the opening and closing of the flow rate controller at timed intervals to control the flow rate of the fluid in the solid phase extraction purification unit (2) and the elution process of the eluent concentration unit (3). The timing module is used to automatically adjust the nitrogen purging intensity and vacuum negative pressure parameters.

5. The system for simultaneous detection of trace PFAS and antibiotics in water according to claim 4, characterized in that: The sample pretreatment unit (1) includes an acid-base module, which is used to provide acidic and alkaline solutions; The control unit (5) receives acid-base electrical signals and flow rate electrical signals. The control unit (5) is electrically connected to the acid-base module. The control unit (5) controls the acid-base module to output acidic or alkaline solutions according to the acid-base electrical signals, so as to adjust the pH of the water sample in the sample pretreatment unit (1). The control unit (5) controls the flow rate controller in real time according to the flow rate electrical signal to control the fluid flow rate.

6. A method for simultaneous detection of trace PFAS and antibiotics in water, applied to the system for simultaneous detection of trace PFAS and antibiotics in water as described in any one of claims 1-5, characterized in that, The method includes: S1: Input the water sample containing the target substance into the sample pretreatment unit (1), and control the homogenization and pH adjustment through the control unit (5). After adjusting to the target pH range, it is transported to the solid phase extraction purification unit (2). The target substances include PFAS and antibiotics. S2: Start the solid phase extraction purification unit (2) and control the adjusted water sample and eluent to flow through the activated solid phase extraction column through the online monitoring unit (4) so ​​that the target substance is effectively adsorbed and the interfering matrix is ​​discharged to ensure that the target substance is fully adsorbed and the interfering matrix is ​​removed. S3: Start the eluent concentration unit (3) and control the linkage gradient elution through the online monitoring unit (4). In sequence, methanol, methanol-water mixture and ammonia-methanol mixture are used as eluents and input into the solid phase extraction column. The eluted liquid is collected, concentrated by nitrogen blowing, and then the volume is adjusted to obtain the test sample, so as to achieve graded gradient elution of the target analyte. S4: The sample enters the liquid chromatography-mass spectrometry (LC-MS) detection unit (6), and the quantitative results are output through chromatographic separation and mass spectrometry detection.

7. The method for simultaneous detection of trace PFAS and antibiotics in water according to claim 6, characterized in that: In step S1, pH adjustment is performed using an acetic acid solution and an ammonia solution, and the target pH range is pH 5.0-pH 7.

0. The activation process involves sequentially passing an ammonia-methanol mixture, methanol, and ultrapure water through the solid-phase extraction column at a flow rate of 1 mL / min to 3 mL / min to thoroughly clean and activate the column.

8. The method for simultaneous detection of trace PFAS and antibiotics in water according to claim 7, characterized in that: In step S2, the loading flow rate of the adjusted water sample is 4 mL / min-6 mL / min, and the rinsing fluid is successively ammonium acetate-acetic acid buffer solution and ultrapure water, with a rinsing flow rate of 1 mL / min-3 mL / min.

9. The method for simultaneous detection of trace PFAS and antibiotics in water according to claim 8, characterized in that: The graded gradient elution includes: The isocratic elution was performed sequentially with pure methanol as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. The isocratic elution was used to capture weakly polar antibiotics. Eluting was performed using a slow slope with a methanol-water mixture containing 5 mM ammonium acetate as the eluent, at a flow rate of 1.0 mL / min to 2.0 mL / min. This slow slope elution was used to balance the ionic binding force and solubility of PFAS. Strong elution was performed using an ammonia-methanol mixture as the eluent at a flow rate of 1.0 mL / min to 2.0 mL / min. This strong elution was used to create an alkaline environment and break the strong ionic bonds between PFAS and the column. The rinsing and elution process uses an ammonia-methanol mixture as the rinsing solution at a flow rate of 1.0 mL / min to 3.0 mL / min. This rinsing and elution is used for impurity removal and activity regeneration of the solid-phase extraction column. The eluents corresponding to isocratic elution, gentle slope elution, and strong elution were collected, concentrated by nitrogen blowing, and then brought to a fixed volume to obtain the test sample.

10. The method for simultaneous detection of trace PFAS and antibiotics in water according to claim 9, characterized in that: The eluent used in the isocratic elution has a methanol mass fraction of 100%, and the flow rate of pure methanol as the eluent is 1.5 mL / min. The eluent for the gentle slope elution contains a methanol solution with 5 mM ammonium acetate in a volume ratio of 2:98 to a pure aqueous solution, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the eluent for strong elution is 1:199, and the elution flow rate is 1.5 mL / min. The volume ratio of ammonia solution to methanol solution in the rinsing solution is 1:99, and the rinsing flow rate is 2.0 mL / min.

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