Sample pretreatment system and method for detecting polycyclic aromatic hydrocarbon in water body

Abstract

The invention relates to the field of sample treatment, in particular to a sample pretreatment system and method for water body polycyclic aromatic hydrocarbon detection. The method comprises the following steps: carrying out matrix state detection on a detection sample to obtain a water body complexity feature set; carrying out water body polycyclic aromatic hydrocarbon phase migration calculation based on the water body complexity feature set to obtain phase migration features; determining an optimal enrichment mode of the current detection sample based on the phase migration characteristics; carrying out enrichment treatment based on the optimal enrichment mode, and extracting an enriched product; setting a purification scheme according to the enriched product; and performing pretreatment purification and qualified sample judgment on the detection sample based on the purification scheme to finish the detection pretreatment operation. The sample detection quality is improved, so that the detection efficiency and accuracy of the polycyclic aromatic hydrocarbon in the water body are improved.

Description

Technical Field

[0001] This invention relates to the field of sample processing, and more particularly to a sample pretreatment system and method for detecting polycyclic aromatic hydrocarbons in water. Background Technology

[0002] With the increasing demands for environmental protection and water quality monitoring, polycyclic aromatic hydrocarbons (PAHs), as typical persistent organic pollutants, have become important indicators for environmental monitoring and risk assessment due to their residual levels and distribution in water bodies. PAHs are widely present in industrial emissions, oil spills, and urban sewage, exhibiting bioaccumulation, high toxicity, and recalcitrant degradation characteristics, posing a potential threat to ecosystems and human health. Therefore, accurate detection of PAHs in water bodies is crucial for environmental governance, public safety assessment, and water quality management. Existing methods for PAH detection in water bodies largely rely on chromatographic analysis techniques, such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS), whose analytical accuracy and sensitivity are highly dependent on the quality of sample pretreatment. Due to the complex matrix characteristics of water bodies, including suspended particles, organic matter, and salts, direct injection often leads to interference with analytical results, resulting in low recovery rates, large quantitative errors, and insufficient detection sensitivity. The distribution states of PAHs (dissolved, particle-bound, or adsorbed) vary significantly among different water samples, making it difficult for traditional one-size-fits-all pretreatment methods to take into account the treatment effects of various types of samples. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a sample pretreatment system and method for detecting polycyclic aromatic hydrocarbons in water, thereby resolving at least one of the aforementioned technical issues.

[0004] To achieve the above objectives, the present invention provides a sample pretreatment method for the detection of polycyclic aromatic hydrocarbons in water, comprising the following steps: Step S1: Perform matrix state detection on the test sample to obtain the water body complexity feature set; Step S2: Calculate the phase migration of polycyclic aromatic hydrocarbons in water based on the water body complexity feature set to obtain the phase migration characteristics; Step S3: Determine the optimal enrichment method for the current sample based on phase transition characteristics; Step S4: Perform enrichment processing based on the optimal enrichment method to extract the enriched product; set a purification plan based on the enriched product; Step S5: Based on the purification plan, perform pretreatment purification on the test samples and determine qualified samples to complete the pretreatment operation.

[0005] This specification provides a sample pretreatment system for detecting polycyclic aromatic hydrocarbons (PAHs) in water, used to perform the sample pretreatment method for PAH detection in water as described above, including: The sample testing module performs matrix state detection on the tested samples to obtain a water body complexity feature set. The migration calculation module performs phase migration calculations of polycyclic aromatic hydrocarbons in water bodies based on the water body complexity feature set, and obtains phase migration characteristics. The enrichment method module determines the optimal enrichment method for the current sample based on phase transition characteristics; The enrichment processing module performs enrichment processing based on the optimal enrichment method to extract the enriched product; and sets a purification scheme based on the enriched product. The sample judgment module performs pretreatment purification on the test samples based on the purification scheme and judges whether the samples are qualified, thus completing the pretreatment operation for testing.

[0006] The specific benefits of this invention are as follows: By detecting the matrix state, information on the physicochemical properties and potential interfering substances in the water sample can be obtained, such as the content of dissolved organic matter, the concentration of suspended particles, pH value, salinity, and conductivity. After constructing a water body complexity feature set, the influence of the water sample matrix on the adsorption, dissolution, or migration of polycyclic aromatic hydrocarbons (PAHs) can be quantitatively described, thereby providing data support for subsequent processing. By clarifying the water body complexity, analytical errors caused by matrix interference can be avoided. For example, water bodies with high suspended matter may lead to insufficient adsorption of PAHs or reduced enrichment efficiency; early identification through the feature set can provide guidance for the selection of enrichment methods. Using the water body complexity characteristics, the migration distribution of PAHs between the aqueous phase, solid phase (suspended particles), sediment, or gas phase can be calculated, i.e., phase migration characteristics. Clarifying the distribution state of PAHs helps in selecting the most suitable enrichment method (e.g., liquid-liquid extraction, solid-phase extraction, adsorbent type, etc.). Optimizing the enrichment method can maximize the capture of target PAHs while reducing the co-enrichment of matrix interfering substances, thereby reducing background noise and improving the accuracy and sensitivity of the analytical signal. After implementing the optimal enrichment scheme, the target PAHs are concentrated and extracted into the enriched product, while reducing the dilution effect caused by the volume of the water sample. By analyzing the component characteristics of the enriched product, targeted purification schemes can be designed, such as removing highly polar interfering substances, suspended particles, salts, or other organic matter. Optimizing the purification scheme in advance can significantly reduce background interference, improve chromatographic resolution and peak shape quality, and make the detection system more sensitive and accurate for low concentrations of PAHs. Purification of the enriched product removes residual interfering substances and impurities, generating samples that can be directly injected into the analytical instrument. The purified samples are then assessed for compliance (e.g., recovery rate, residual interfering substance index) to ensure stable and reliable sample quality before entering the detection stage. Attached Figure Description

[0007] Figure 1This is a schematic flowchart of the sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to the present invention. Figure 2 This is a detailed flowchart illustrating the implementation steps of step S1. Figure 3 This is a flowchart illustrating the detailed implementation steps of step S2. Detailed Implementation

[0008] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0009] This application provides a sample pretreatment system and method for detecting polycyclic aromatic hydrocarbons (PAHs) in water. The execution entities of the sample pretreatment system and method for detecting PAHs in water include, but are not limited to, mechanical equipment, data processing platforms, cloud server nodes, and network upload devices mounted on the system, which can be considered as general computing nodes in this application. The data processing platform includes, but is not limited to, at least one of an audio-visual management system, an information management system, and a cloud-based data management system.

[0010] Please see Figures 1 to 3 This invention provides a sample pretreatment method for the detection of polycyclic aromatic hydrocarbons (PAHs) in water, comprising the following steps: Step S1: Perform matrix state detection on the test sample to obtain the water body complexity feature set; Step S2: Calculate the phase migration of polycyclic aromatic hydrocarbons in water based on the water body complexity feature set to obtain the phase migration characteristics; Step S3: Determine the optimal enrichment method for the current sample based on phase transition characteristics; Step S4: Perform enrichment processing based on the optimal enrichment method to extract the enriched product; set a purification plan based on the enriched product; Step S5: Based on the purification plan, perform pretreatment purification on the test samples and determine qualified samples to complete the pretreatment operation.

[0011] In the embodiments of the present invention, see Figure 1 This is a schematic flowchart of a sample pretreatment method for detecting polycyclic aromatic hydrocarbons (PAHs) in water according to the present invention. In this example, the sample pretreatment method for detecting PAHs in water includes the following steps: Step S1: Perform matrix state detection on the test sample to obtain the water body complexity feature set; In this embodiment, during the pretreatment process for polycyclic aromatic hydrocarbon (PAH) detection in water, matrix state analysis is performed on the collected samples to comprehensively understand the key physicochemical characteristics affecting the distribution and enrichment behavior of PAHs in the water. A comprehensive analysis of multiple parameters, including turbidity, dissolved organic carbon content, particulate matter size distribution, salinity gradient, and natural fluorescence response characteristics, is conducted to construct a water complexity feature set. Turbidity typically covers the range of 0–100 NTU and is used to characterize the suspended particulate matter load level; dissolved organic carbon content generally falls within the range of 0.5–20 mg / L and is an important indicator for assessing the complexity of the organic matrix; particulate matter size distribution focuses on the concentrated range and distribution width within the range of 0.1–50 μm; salinity gradient can vary from 0–5‰ to reflect the influence of ionic strength on the behavior of hydrophobic pollutants; and the natural fluorescence response is described by the response intensity within the characteristic range of aromatic organic compounds.

[0012] Step S2: Calculate the phase migration of polycyclic aromatic hydrocarbons in water based on the water body complexity feature set to obtain the phase migration characteristics; In this embodiment, after obtaining the water body complexity feature set, it is coupled with the physicochemical properties of polycyclic aromatic hydrocarbons (PAHs) to determine the phase distribution and migration trend of PAHs in the water body. The focus is on the transfer characteristics of PAHs between the dissolved phase, the particulate adsorbed phase, and the colloidal bound phase. When the water turbidity is higher than 30 NTU and the particle size is concentrated in the 1–10 μm range, PAHs are more likely to migrate to the particulate adsorbed phase; when the dissolved organic carbon content is higher than 8 mg / L and the natural fluorescence response is strong, PAHs tend to bind with colloidal organic matter; under conditions of low turbidity, low DOC, and gradual salinity changes, PAHs are mainly in the dissolved phase. By comprehensively analyzing these characteristics, a phase migration characteristic reflecting the direction and intensity of PAH phase transfer can be formed.

[0013] Step S3: Determine the optimal enrichment method for the current sample based on phase transition characteristics; In this embodiment, after clarifying the phase migration characteristics of polycyclic aromatic hydrocarbons (PAHs), the most suitable enrichment method for the current sample is determined based on its dominant occurrence phase. If the phase migration characteristics indicate that the dissolved phase is dominant and the particle loading is low, a liquid-phase enrichment method with the target analyte in the aqueous phase as the core is preferred. If the proportion of the adsorbed particle phase is high and the PAHs are highly hydrophobic, an enrichment method based on particle desorption is selected. When the dissolved phase, the adsorbed particle phase, and the colloidal bound phase all have significant proportions, a composite enrichment method is used. The selection of the enrichment method also needs to comprehensively consider the volume of the water sample to be processed (usually 500 mL to 5 L), the expected concentration factor of the target analyte (50–500 times), and the overall processing time cost.

[0014] Step S4: Perform enrichment processing based on the optimal enrichment method to extract the enriched product; set a purification plan based on the enriched product; In this embodiment, after determining the optimal enrichment method, the sample is enriched according to the corresponding path to concentrate polycyclic aromatic hydrocarbons into a smaller volume of enriched phase. After enrichment, the volume of the enriched product is generally controlled within the range of 5–20 mL to meet subsequent purification requirements. Based on the overall response characteristics of the enriched product, the matrix components that may be introduced are identified, and a targeted purification scheme is set accordingly. The purification scheme includes the combination of adsorbent materials, the composition ratio of the elution solvent, and the setting of the elution order. For example, when there are many aromatic interfering substances in the enriched product, adsorbent materials selective for aromatic structures can be preferentially selected; the elution solvent can be gradually adjusted from low polarity to medium polarity to achieve effective separation of the target analyte and interfering substances.

[0015] Step S5: Based on the purification plan, perform pretreatment purification on the test samples and determine qualified samples to complete the pretreatment operation.

[0016] In this embodiment, under the guidance of a predetermined purification scheme, pretreatment purification operations are performed on the enriched products to reduce matrix interference and stabilize the response characteristics of the target polycyclic aromatic hydrocarbons (PAHs). After purification, the samples are judged for compliance by comprehensively evaluating indicators such as solvent compatibility, target concentration factor, and baseline interference level. When the purification analysis results meet the preset detection reliability requirements, the sample is marked as a qualified sample and directly enters the subsequent PAH detection process; when the purification analysis results are lower than the requirements, the sample is judged as unqualified and rejected.

[0017] In this embodiment, see Figure 2 The diagram below illustrates the detailed implementation steps of step S1. In this embodiment, the detailed implementation steps of step S1 include: The matrix state of the test sample is detected to generate water state parameters; Based on the water state parameters, the matrix dispersion index, organic interference potential coefficient and particle adsorption activity index are calculated to obtain the water body complexity feature set. The water state parameters include water sample turbidity, dissolved organic carbon content, particulate matter size distribution, salinity gradient, and natural fluorescence response parameters. The turbidity of the sample is measured using a turbidimeter to extract the turbidity of the water sample; The dissolved organic carbon content was obtained by non-dispersive infrared detection using a TOC analyzer. Dynamic optical dispersion analysis was performed on the test samples to determine the particle size distribution. The salinity gradient is obtained by converting the conductivity of the sample using a conductivity meter. Wavelength excitation scanning is performed using a fluorescence spectrometer to output natural fluorescence response parameters.

[0018] In this embodiment, key matrix factors affecting the distribution, enrichment, and extraction efficiency of PAHs in water are systematically characterized using multidimensional detection methods. Water samples should be stored in brown glass bottles at 4 °C in the dark, and matrix state detection should be completed within 24 hours to avoid degradation or structural changes of organic components. Matrix state detection is not a single-parameter measurement, but rather a synergistic analysis of multiple indicators such as turbidity, dissolved organic carbon, particulate matter size distribution, salinity gradient, and natural fluorescence to construct a comprehensive water state parameter system. During the detection process, all parameters must be completed on the same batch of water samples to ensure data comparability and consistency. The raw data obtained through standardized detection procedures will serve as input parameters for subsequent calculations of the matrix dispersion index, organic interference potential coefficient, and particle adsorption activity index, thereby achieving a quantitative description of the complexity of the water matrix.

[0019] Water state parameters are a fundamental set of data characterizing the matrix features of water samples, mainly including turbidity, dissolved organic carbon content, particulate matter size distribution, salinity gradient, and natural fluorescence response parameters. These parameters reflect the influence of water bodies on the behavior of polycyclic aromatic hydrocarbons (PAHs) from physical, chemical, and spectral response perspectives. Turbidity characterizes the overall content and dispersion state of suspended particulate matter in the water, directly affecting the partitioning behavior of PAHs between the aqueous and particulate phases. Dissolved organic carbon content reflects the level of small molecules and humic organic matter in the water, and is an important factor affecting the solubility and extraction efficiency of PAHs. Particulate matter size distribution determines the specific surface area and adsorption capacity of particles. The salinity gradient affects the dissolution and precipitation behavior of organic pollutants by changing the ionic strength of the water. Natural fluorescence response parameters characterize the spectral characteristics of aromatic organic matter and humic substances in the water, and are closely related to the potential interference of PAHs in spectral detection.

[0020] The matrix condition testing is as follows: Turbidity of the water sample is measured using a standard turbidimeter. The instrument must be calibrated at two or more points using 0 NTU and 20 NTU standard formalin solution to ensure measurement accuracy. During testing, the well-mixed water sample is slowly poured into a dedicated colorimetric tube, avoiding the formation of air bubbles or the attachment of contaminants. The outer wall of the colorimetric tube must be wiped clean with a non-woven cloth to prevent fingerprints or water stains from affecting the optical path. The turbidimeter calculates the turbidity value by measuring the intensity of the incident light scattered by the water sample; the detection wavelength is typically 860 nm. Each sample is measured at least three times, and the average value is taken as the final turbidity result. When the turbidity of the water sample exceeds the instrument's upper limit (e.g., 1000 NTU), it should be diluted appropriately with deionized water, and the dilution factor should be recorded. The obtained turbidity data is used to assess the content of suspended particulate matter in the water and its impact on the adsorption and extraction processes of PAHs.

[0021] Dissolved organic carbon (DOC) was determined using a total organic carbon (TOC) analyzer combined with non-dispersive infrared (NDIR) detection. Before measurement, the water sample was filtered through a 0.45 μm glass fiber membrane to remove suspended particulate matter, ensuring that the measured object was dissolved organic carbon. After filtration, the pH of the water sample was adjusted to approximately 2 with the addition of dilute hydrochloric acid, and then allowed to stand under nitrogen purging for 5–10 minutes to remove interference from inorganic carbon. During instrument operation, the organic carbon in the water sample was converted into carbon dioxide under high-temperature combustion or ultraviolet oxidation conditions. The generated CO2 was then quantitatively analyzed using an NDIR detector. The commonly used measurement range was 0–50 mg / L, with repeatability controlled within ±2%. DOC content data was used to assess the complexing, encapsulation, and detection interference effects of organic matrices in the water on PAHs.

[0022] The particle size distribution was determined using dynamic light scattering (DLS) technology. Before detection, the water sample underwent mild ultrasonic treatment (e.g., 40 kHz, 1–2 min) to break up weakly aggregated particles, but excessive ultrasonication was avoided to prevent particle structure damage. The sample was then injected into a dedicated quartz cuvette and kept at a constant temperature (typically 25 ℃) to reduce errors caused by Brownian motion. The DLS instrument recorded the fluctuations in the intensity of scattered light generated by the particles under laser irradiation and calculated the hydrodynamic diameter of the particles using an autocorrelation function. The detection angle was set to 173°, and the measurement time was 60–120 s. The obtained particle size distribution results, including average particle size, particle size distribution width, and multi-peak characteristics, were used to analyze the adsorption capacity of particulate matter in water and its impact on the migration behavior of PAHs.

[0023] The salinity gradient of water is obtained by measuring and converting using a conductivity meter. The conductivity meter needs to be calibrated using a standard KCl solution (e.g., 1413 μS / cm). During measurement, the electrode is completely immersed in the water sample, gently stirred to eliminate the influence of air bubbles, and the conductivity value is recorded after the reading stabilizes. The water sample temperature needs to be controlled during the detection process; generally, the instrument's built-in temperature compensation function is used to uniformly convert the data to 25 ℃. Subsequently, the conductivity value is converted into a salinity parameter according to empirical formulas or built-in programs. The salinity gradient reflects the change in ionic strength of the water body.

[0024] Natural fluorescence response parameters were obtained using a fluorescence spectrometer with wavelength excitation scanning. Before detection, the water sample was filtered through a 0.45 μm filter to reduce scattering interference. The excitation wavelength range was set to 200–450 nm, the emission wavelength range to 250–600 nm, and the step interval to 5 nm. During scanning, the slit width was kept consistent (e.g., 5 nm), and the scanning speed was controlled to ensure a good signal-to-noise ratio. The obtained three-dimensional fluorescence spectra can be used to extract characteristic peak positions, peak intensities, and fluorescence index parameters, which are closely related to the content of aromatic organic matter and humic substances in the water.

[0025] Dispersed physicochemical parameters are transformed into comprehensive indicators with clear physical meaning to assess the potential impact of water bodies on the detection process of polycyclic aromatic hydrocarbons (PAHs). The matrix dispersion index primarily reflects the degree of heterogeneity of particulate matter and dissolved components in the water body, and its calculation is typically based on parameters such as particle size distribution width and turbidity fluctuation range. The organic interference potential coefficient is used to quantify the competitive or masking effects of dissolved organic carbon and naturally fluorescent active components on PAH extraction and detection signals. The particulate adsorption activity index comprehensively considers the specific surface area of ​​particulate matter, the particle size concentration range, and its affinity characteristics with organic pollutants. Each indicator needs to be dimensionless before calculation to eliminate the influence of differences in the dimensions of different parameters.

[0026] In this embodiment, see Figure 3 The diagram below illustrates the detailed implementation steps of step S2. In this embodiment, the detailed implementation steps of step S2 include: Based on the water body complexity feature set, the phase distribution ratio of polycyclic aromatic hydrocarbons in water bodies is analyzed to obtain the distribution ratio parameters; the distribution ratio parameters include dissolved phase, particulate adsorption phase and colloidal bound phase. Extracting a chemical information database of polycyclic aromatic hydrocarbons (PAHs); identifying the hydrophobicity constants and molecular size characteristics of PAHs with different ring numbers based on the PAH chemical information database; Based on the hydrophobicity constant and molecular size characteristics, the phase migration of water bodies is calculated using the allocation ratio parameters to obtain phase migration characteristics.

[0027] In this embodiment, based on parameters such as particulate matter content, particle size distribution range, dissolved organic carbon level, natural fluorescence response intensity, and salinity gradient variation in the water body, the preferred occurrence forms of polycyclic aromatic hydrocarbons (PAHs) in each phase are determined by comprehensively evaluating the physical dispersion characteristics and organic matrix characteristics of the water body. When the water turbidity is in the range of 20–100 NTU, the median particle size is less than 10 μm, and the particle adsorption activity index is high, PAHs tend to bind to the particle surface. When the dissolved organic carbon content is in the range of 5–15 mg / L and the natural fluorescence peak intensity is high, PAHs are more likely to exist in a colloidal form. Under conditions of low turbidity, low DOC, and small salinity gradient, PAHs are mainly in the dissolved phase. Based on the phase distribution analysis, the three main existence forms of PAHs in the water body are further quantified and described, forming the distribution ratio parameters of the dissolved phase, particle adsorption phase, and colloidal phase. The proportion of the dissolved phase is mainly affected by the ionic strength of the water body, the range of salinity gradient (e.g., 0.5–5‰), and the proportion of low-molecular-weight dissolved organic carbon components. The proportion of the particulate adsorption phase is closely related to the particle concentration, particle size distribution width, and particle specific surface area; when the particle size is concentrated in the 1–5 μm range, the adsorption capacity is significantly enhanced. The proportion of the colloidal bound phase is mainly related to the content of colloidal organic matter, the fluorescence humic index, and the proportion of aromatic components in DOC. By classifying and integrating the various parameters of the water body complexity characteristics, relative weight values ​​can be assigned to the three phases, and these can be transformed into standardized allocation ratio parameters.

[0028] To achieve refined analysis of the phase behavior of different polycyclic aromatic hydrocarbons (PAHs) in water, a PAH chemical information database is needed to organize the structural characteristics and physicochemical properties of target compounds. This database covers representative compounds of 2- to 6-ring PAHs, including the range of hydrophobicity constants, molecular weight ranges, maximum molecular cross-section, and molecular volume characteristics. Low-ring PAHs typically have molecular weights below 200 g / mol and molecular sizes less than 0.7 nm; high-ring PAHs can have molecular weights exceeding 250 g / mol and molecular sizes exceeding 1.0 nm. By standardizing these parameters, a standardized set of chemical characteristic parameters can be formed for matching analysis with a set of water body complexity characteristics.

[0029] Based on a chemical information database, the hydrophobicity constants and molecular size characteristics of polycyclic aromatic hydrocarbons (PAHs) with different ring numbers are classified and identified. 2–3 ring PAHs typically exhibit low hydrophobicity, with hydrophobicity constants ranging from 3.0 to 4.5. Their relatively compact molecular structure makes them more likely to enter the dissolved phase of water or bind to small colloidal organic matter. 4 ring PAHs exhibit moderate hydrophobicity, with hydrophobicity constants of approximately 4.5–5.5, showing a transitional characteristic between the dissolved phase and the particulate adsorption phase. 5–6 ring PAHs exhibit significantly enhanced hydrophobicity, with hydrophobicity constants typically greater than 6.0. Their larger molecular size makes them more prone to adhering to particle surfaces. By identifying and grouping these characteristics, different PAHs can be assigned phase preference labels. After obtaining the allocation ratio parameters and chemical characteristic parameters of PAHs, it is necessary to analyze the phase migration behavior of PAHs in water. This process determines the likelihood of PAHs transferring between different phases by comparing the matching relationship between the water complexity feature set and the hydrophobicity and molecular size of PAHs. When the particulate matter content in water increases and the adsorption activity of particles is enhanced, highly hydrophobic polycyclic aromatic hydrocarbons (PAHs) with multi-ring structures are more likely to transfer from the dissolved phase to the particulate adsorption phase. When the dissolved organic carbon content increases and the natural fluorescence response is enhanced, medium- and low-ring PAHs are more likely to migrate from the dissolved phase to the colloidal bound phase. An increase in salinity gradient can also promote the "salting out" behavior of some PAHs, thereby strengthening the tendency to transfer to the non-dissolved phase.

[0030] By integrating phase distribution ratio parameters with phase migration analysis results, a phase migration characteristic of polycyclic aromatic hydrocarbons (PAHs) under specific water conditions is formed. This characteristic describes the relative stability and migration tendency of PAHs among the dissolved phase, particulate adsorbed phase, and colloidal bound phase. During sample pretreatment, the treatment strategy can be adjusted based on this characteristic. For example, when the proportion of particulate adsorbed phase is high, the particulate phase enrichment step can be strengthened; when the colloidal bound phase is significant, the organic matrix purification intensity can be increased, thereby improving the overall recovery efficiency and detection reliability of PAHs.

[0031] In this embodiment, step S3 includes the following steps: Define candidate enrichment methods; the candidate enrichment methods include liquid phase enrichment path, particle desorption path and composite enrichment path; Based on phase transition characteristics, data are input into candidate enrichment methods to calculate the expected recovery efficiency of the target material, the degree of potential matrix interference introduction, and the processing time cost of different candidate enrichment methods, thereby obtaining enrichment evaluation indicators. The optimal enrichment method for the current sample is determined based on enrichment evaluation indicators.

[0032] In this embodiment, the candidate enrichment methods mainly include three categories: liquid-phase enrichment pathway, particle desorption pathway, and composite enrichment pathway. The liquid-phase enrichment pathway targets dissolved phases and some colloidal bound phases of polycyclic aromatic hydrocarbons (PAHs) in the water body. It typically relies on organic solvent extraction or the enrichment capacity of solid-phase adsorption materials for the target analytes in the aqueous phase, and is suitable for water bodies with turbidity below 10 NTU and dissolved organic carbon content below 5 mg / L. The particle desorption pathway focuses on PAHs in the particle-adsorbed phase, releasing the target analytes through desorption treatment of particles. It is suitable for water bodies with high particle content, particle size concentrated in the 1–20 μm range, and a large proportion of particle-adsorbed phase. The composite enrichment pathway combines liquid-phase enrichment and particle desorption, and is suitable for situations where the phase distribution is relatively dispersed, the proportion of colloidal bound phase is significant, and the water body is highly complex. The liquid-phase enrichment pathway primarily targets freely dissolved and weakly bound polycyclic aromatic hydrocarbons (PAHs) in water. Its processing logic aims to concentrate the target compounds from a large-volume water sample into a smaller enrichment phase while maintaining the overall stability of the water body's structure. This pathway is typically suitable for water sample volumes ranging from 500 mL to 2 L and salinity gradients less than 2‰. During enrichment, the contact time between the liquid phase and the adsorption medium or extraction phase is generally controlled within 30–60 min to ensure sufficient transfer of PAHs with hydrophobicity constants in the range of 3.0–5.0. The liquid-phase enrichment pathway is sensitive to particulate matter content; when turbidity exceeds 20 NTU, particle masking effects may lead to decreased recovery efficiency and introduce additional matrix interference. The advantages of this pathway are its relatively simple processing flow and short single-process time, with the overall time typically controlled within the range of 1–2 h. However, under high organic matrix background conditions, it is prone to co-enrichment of non-target organic compounds.

[0033] The particulate desorption pathway is primarily designed for polycyclic aromatic hydrocarbons (PAHs) distributed in environments where the adsorbate phase is predominantly particulate. Its core principle is to first separate particulate matter from the water, and then release the target analytes adsorbed on the particle surface through desorption. This pathway is suitable for water conditions with turbidity exceeding 30 NTU, high particulate concentration, and a particulate adsorption phase ratio exceeding 40%. The particulate separation stage typically corresponds to particles larger than 0.7 μm. The desorption process needs to be carried out under appropriate solvent polarity conditions to enhance the desorption capacity for high-ring PAHs with a hydrophobicity constant greater than 5.5. The desorption time is generally controlled within 20–40 min, and the desorption temperature can be set within the range of 30–50 °C to improve the molecular diffusion rate. The advantage of the particulate desorption pathway lies in its high recovery potential for high-ring and polycyclic PAHs; however, the processing flow is relatively complex, with an overall time cost typically exceeding 2–3 hours. Furthermore, it requires high operational stability and uniformity in particle processing.

[0034] The composite enrichment pathway is a combination of liquid-phase enrichment and particle desorption pathways, suitable for situations with complex phase distributions and generally high overall water complexity characteristic set values. When the proportion of colloidal bound phase reaches 20-40%, and both dissolved and particle adsorbed phases constitute a certain proportion, a single enrichment method is insufficient to cover all target analytes. The composite enrichment pathway typically involves first performing phase separation treatment on the water, guiding the dissolved, colloidal, and particle phases to different treatment units, and then merging the enriched products from each part. This pathway usually processes large water sample volumes, ranging from 2 to 5 L, and the total treatment time is relatively long, generally between 3 and 4 hours, but it can maintain a relatively stable recovery level over a wide range of hydrophobicity constants. The composite enrichment pathway has relatively strong control over matrix interference, but the operation steps are numerous, requiring significant time and resources.

[0035] After clarifying the processing logic of the candidate enrichment methods, the phase migration characteristics obtained in the early stage need to be used as input conditions to evaluate the applicability of different enrichment methods. The evaluation mainly includes three aspects: the expected recovery efficiency of the target analyte, the degree of potential matrix interference, and the processing time cost. The expected recovery efficiency focuses on the enrichment potential of polycyclic aromatic hydrocarbons (PAHs) in different hydrophobicity constant ranges under the corresponding enrichment pathways. For example, PAHs with a hydrophobicity constant less than 4.5 usually have a higher expected recovery under the liquid phase enrichment pathway, while PAHs with a hydrophobicity constant greater than 6.0 are more advantageous under the particulate desorption pathway. The degree of matrix interference is mainly evaluated by combining DOC content, natural fluorescence response intensity, and the proportion of particulate organic matter to determine the risk of non-target organic matter entering the enrichment phase. The processing time cost comprehensively considers the single processing time, water sample volume, and step complexity, and conducts a horizontal comparison of different enrichment methods. After obtaining the enrichment evaluation indicators corresponding to each candidate enrichment method, the evaluation results need to be comprehensively weighed to determine the optimal enrichment method for the current sample. This process does not simply pursue the highest recovery efficiency, but rather needs to strike a balance between recovery efficiency, matrix disturbance control capabilities, and processing time costs. When the water phase structure is relatively simple and the dissolved phase is dominant, the liquid phase enrichment pathway can usually meet the recovery and efficiency requirements; when the particulate adsorption phase is obvious and the proportion of high-ring polycyclic aromatic hydrocarbons is high, the particulate desorption pathway is more advantageous; while in the case of dispersed phase distribution and high water body complexity, the composite enrichment pathway can provide more stable overall performance. In this embodiment, step S4 includes the following steps: Enrichment processing is performed based on the optimal enrichment method, and the enriched products are scanned and extracted. Identify and label interfering components in the enriched products; The coexistence risk of the interfering component with polycyclic aromatic hydrocarbons during co-elution or co-adsorption is calculated to obtain the risk assessment results; The purification plan is dynamically set based on the risk assessment results. The purification plan includes the combination of adsorption materials, the composition of the elution solvent, and the elution sequence.

[0036] In this embodiment, after determining the optimal enrichment method, the sample is enriched according to the corresponding path to effectively transfer polycyclic aromatic hydrocarbons (PAHs) from a large volume water sample to a small volume enriched phase. If liquid phase enrichment is selected, the water sample volume is typically controlled within the range of 500 mL to 2 L, and the contact time of the enrichment medium is set at 30–60 min to cover PAHs with hydrophobicity constants in the range of 3.0–5.5. If particle desorption is used, particles larger than 0.7 μm in the water are separated, and then desorption is performed under moderate heating conditions. The desorption temperature is generally set in the range of 35–50 °C, and the duration is controlled at 20–40 min. If a composite enrichment method is used, the process is carried out in the order of phase separation, separate enrichment, and then merging. After enrichment, the resulting enriched phase is controlled within a volume range of 5–20 mL to increase the concentration level of the target analyte in subsequent processing. After obtaining the enriched product, a comprehensive scanning analysis is required to initially understand the compositional characteristics of the target and non-target components. The scanning method typically combines ultraviolet (UV) and fluorescence response ranges for multidimensional observation. UV scanning wavelengths can be set in the 200–400 nm range to identify components with dense aromatic structures; fluorescence scanning covers the excitation wavelength range of 200–450 nm and the emission wavelength range of 250–600 nm to determine the presence of humic substances and aromatic-like organic compounds. During scanning, the volume of the enriched product is maintained within 1–2 mL to reduce solvent background interference. By comparing the scanning results, the relatively concentrated range of polycyclic aromatic hydrocarbon (PAH) signals in the enriched product can be identified, and obviously irrelevant solvent background signals can be excluded.

[0037] Further identification and labeling of components that may interfere with the detection of polycyclic aromatic hydrocarbons (PAHs) were conducted. Interfering components mainly include natural organic derivatives, aliphatic long-chain organic compounds, residual surfactants, and some aromatic non-target compounds. These components typically exhibit broad absorption peaks in UV scanning and non-characteristic emission signals in fluorescence scanning. By analyzing peak width, response intensity changes, and response range distribution in the scan spectra, components with a high degree of overlap with the characteristic response ranges of PAHs were labeled as potential interfering components. During labeling, hydrophobicity was considered; when the hydrophobic characteristics of interfering components were similar to those of 4–6 ring PAHs, their impact on subsequent separation and detection was relatively high. After labeling, a classification description of interfering components in the enriched products was generated, providing a basis for risk assessment. The possibility of co-elution or co-adsorption between interfering components and PAHs during subsequent processing was assessed. This risk mainly depends on the similarity between the interfering components and PAHs in hydrophobicity, molecular size, and aromatic structural characteristics. When the hydrophobic region of the interfering component overlaps significantly with that of polycyclic aromatic hydrocarbons (PAHs) and the molecular size is in the range of 0.6–1.0 nm, the probability of it competing with the target analyte on the surface of the adsorbent material or during elution increases significantly.

[0038] The purification scheme mainly includes three aspects: the combination of adsorption materials, the composition of the elution solvent, and the elution sequence. For adsorption material selection, silica gel, alumina, or carbon-based adsorption materials can be combined according to the risk level of interfering components to cover different polarities and structural characteristics. The composition of the elution solvent can be adjusted in a gradient between non-polar and weakly polar solvents; for example, the separation effect caused by differences in hydrophobicity can be controlled by adjusting the solvent ratio. The elution sequence is optimized based on the elution strength relationship between the target polycyclic aromatic hydrocarbon and the interfering components, so that the interfering components are preferentially eluted or retained.

[0039] In this embodiment, step S5 includes the following steps: Based on the purification scheme, the test samples are pretreated and purified, and the solvent compatibility index, target concentration factor and baseline interference risk value are calculated by mass spectrometry. Based on the solvent compatibility index, target concentration factor, and baseline interference risk value, sample stability was assessed to obtain purification analysis results; Based on the purification analysis results, qualified samples are determined, and the pre-testing treatment is completed.

[0040] In this embodiment, after dynamically setting the purification scheme, the enriched product of the test sample needs to be pretreated and purified according to the determined combination of adsorbent materials, composition of elution solvent, and elution sequence. The purification operation aims to reduce matrix interference and maintain the structural integrity of polycyclic aromatic hydrocarbons. The volume of the enriched product is usually controlled within the range of 5–10 mL to ensure that the concentration of the target analyte remains within a controllable range. During the purification process, the enriched product passes sequentially through the selected adsorbent material layer. The packing amount of the adsorbent material is generally controlled between 500–2000 mg, depending on the complexity of the interfering components in the enriched product. The elution solvent is switched in a progressive order from low polarity to medium polarity, with each elution volume typically being 5–15 mL, to achieve effective separation of the target analyte from the interfering components. By controlling the elution rate within the range of 1–2 mL / min, problems such as adsorbent material saturation or incomplete elution can be avoided. After purification, the resulting eluent is the purified pretreatment sample. Following the acquisition of the purified pretreatment sample, the compatibility of the solvent system needs to be evaluated using mass spectrometry response characteristics to form a solvent compatibility index. This index reflects the degree of matching between the current elution solvent and the mass spectrometry analysis conditions, focusing on solvent volatility, ionization suppression, and background noise levels. During the evaluation, the changes in background response intensity within the full mass spectrum scan range (e.g., m / z 50–500) are observed to determine whether the solvent itself introduces significant non-target signals. When the background ion response remains stable in the low-mass range without a significant baseline rise, the solvent compatibility is considered good. The location and intensity of residual solvent peaks can also be used for judgment; when solvent-related signals are concentrated in a specific m / z range and do not overlap with the characteristic range of polycyclic aromatic hydrocarbons, the compatibility evaluation is high.

[0041] The mass spectrometry response intensity of the purified sample was compared with the corresponding response range of the water sample before pretreatment, with a focus on signal changes in the typical mass number range of 2–6 ring polycyclic aromatic hydrocarbons (PAHs). When the PAH response peak intensity in the purified sample significantly increased, and the peak shape remained symmetrical with a stable half-width, it indicated a relatively ideal concentration effect. Generally, a concentration factor of 50–500 times is considered suitable, meeting the detection sensitivity requirements without introducing additional matrix interference due to over-concentration. After completing solvent compatibility and target concentration factor analysis, the baseline stability of the purified sample also needs to be evaluated to determine whether potential matrix interference still exists. The baseline interference risk value is mainly determined based on the baseline fluctuation amplitude, noise level, and distribution of non-characteristic peaks during mass spectrometry scanning. When the baseline remains relatively stable throughout the scanning range, and the noise amplitude is less than 5–10% of the target peak height, the baseline interference risk is low; if continuous increases or irregular fluctuations occur near the characteristic mass number of PAHs, it indicates the presence of co-eluting or co-adsorbing interfering components. By comprehensively evaluating baseline fluctuation amplitude, noise density, and the frequency of interference peaks, a baseline interference risk value can be generated. After obtaining the solvent compatibility index, target analyte concentration factor, and baseline interference risk value, a comprehensive evaluation of the overall stability of the purified sample is necessary. Sample stability mainly focuses on whether the purified sample can maintain signal consistency, baseline stability, and target analyte response reliability during subsequent detection processes. When the solvent compatibility index is at an optimal level, the target analyte concentration factor is within a reasonable range, and the baseline interference risk value is low, the sample can be considered to have high stability. Conversely, if any indicator shows abnormalities, the purification protocol may need to be readjusted.

[0042] In this embodiment, the specific steps for determining the qualified samples based on the purification analysis results and completing the pre-testing treatment are as follows: The determination is made based on the purification analysis results and the preset detection reliability threshold. If the purification analysis results are not less than the preset detection reliability threshold, the sample is marked as qualified and the pre-detection processing is completed. If the purification analysis result is less than the preset detection reliability threshold, the sample is marked as unqualified and is removed from the test.

[0043] In this embodiment, after completing the sample pretreatment and purification and obtaining the purification analysis results, the results need to be compared with a preset detection reliability threshold to determine whether the sample meets the conditions for entering the formal detection process. The detection reliability threshold is a comprehensive evaluation limit set during the pretreatment process design stage based on the sensitivity of the detection target, instrument stability requirements, and historical sample processing experience. Its composition typically refers to a reasonable range of solvent compatibility index, target concentration factor, and baseline interference risk value. For example, when solvent compatibility exhibits stable background response and no obvious ion suppression characteristics, the target concentration factor is in the range of 100–400 times, and the baseline interference risk is controlled at a low fluctuation level, the corresponding purification analysis results can be considered to meet the reliable detection requirements. When the purification analysis results reach or exceed the preset detection reliability threshold, it indicates that the sample has achieved a good matrix purification effect and target enrichment level during the pretreatment stage. At this point, the sample is marked as qualified and determined to be a sample that can enter the formal polycyclic aromatic hydrocarbon (PAH) detection process. Qualified samples typically exhibit a stable mass spectrometry baseline, clear target polycyclic aromatic hydrocarbon signals, symmetrical peak shapes, and a signal-to-noise ratio higher than the predetermined requirements, for example, a target peak height to background noise ratio greater than 10. After qualification labeling, the sample can be directly transferred to the subsequent quantitative analysis or confirmatory analysis stage without further pretreatment.

[0044] After marking qualified samples, a final confirmation of the sample pretreatment process is required to ensure that the sample condition remains stable before entering the detection stage. This confirmation process mainly focuses on whether the sample solvent composition is compatible with the detection method, whether the sample volume is within the set range, and whether the sample storage conditions meet the short-term stability requirements. Generally, the volume of qualified samples is controlled within the range of 1–2 mL, and the solvent composition is consistent with the detection injection conditions to avoid signal fluctuations caused by solvent incompatibility.

[0045] When the purification analysis result is lower than the preset detection reliability threshold, it indicates that the current sample still has a high risk of matrix interference or insufficient enrichment of the target analyte after pretreatment and purification. Such samples typically exhibit significant fluctuations in the mass spectrometry baseline, high background noise, or insufficient signal intensity of the target polycyclic aromatic hydrocarbon (PAH) to meet reliable quantification requirements, for example, a signal-to-noise ratio below 5. In this case, the sample is marked as unqualified and its entry into subsequent detection processes is terminated. After marking unqualified samples, they need to be rejected. Rejection involves stopping further pretreatment and detection operations on the sample and removing it from the sample queue.

[0046] In this embodiment, a sample pretreatment system for detecting polycyclic aromatic hydrocarbons (PAHs) in water is provided, which performs the sample pretreatment method for detecting PAHs in water as described above, including: The sample testing module performs matrix state detection on the tested samples to obtain a water body complexity feature set. The migration calculation module performs phase migration calculations of polycyclic aromatic hydrocarbons in water bodies based on the water body complexity feature set, and obtains phase migration characteristics. The enrichment method module determines the optimal enrichment method for the current sample based on phase transition characteristics; The enrichment processing module performs enrichment processing based on the optimal enrichment method to extract the enriched product; and sets a purification scheme based on the enriched product. The sample judgment module performs pretreatment purification on the test samples based on the purification scheme and judges whether the samples are qualified, thus completing the pretreatment operation. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and scope of the equivalents of the application are intended to be included within the invention.

[0047] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein are implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water, characterized in that, Includes the following steps: Step S1: Perform matrix state detection on the test sample to obtain the water body complexity feature set; Step S2: Calculate the phase migration of polycyclic aromatic hydrocarbons in water based on the water body complexity feature set to obtain the phase migration characteristics; Step S3: Determine the optimal enrichment method for the current sample based on phase transition characteristics; Step S4: Perform enrichment processing based on the optimal enrichment method and extract the enriched product; A purification plan should be developed based on the enriched products; Step S5: Based on the purification plan, perform pretreatment purification on the test samples and determine qualified samples to complete the pretreatment operation.

2. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 1, characterized in that, The specific steps of step S1 are as follows: The matrix state of the test sample is detected to generate water state parameters; Based on the water state parameters, the matrix dispersion index, organic interference potential coefficient, and particle adsorption activity index are calculated to obtain the water body complexity feature set.

3. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 2, characterized in that, The specific steps for performing matrix state detection on the test sample to generate water state parameters are as follows: The water state parameters include water sample turbidity, dissolved organic carbon content, particulate matter size distribution, salinity gradient, and natural fluorescence response parameters. The turbidity of the sample is measured using a turbidimeter to extract the turbidity of the water sample; The dissolved organic carbon content was obtained by non-dispersive infrared detection using a TOC analyzer. Dynamic optical dispersion analysis was performed on the test samples to determine the particle size distribution. The salinity gradient is obtained by converting the conductivity of the sample using a conductivity meter. Wavelength excitation scanning is performed using a fluorescence spectrometer to output natural fluorescence response parameters.

4. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 1, characterized in that, The specific steps of step S2 are as follows: Based on the water body complexity feature set, the phase distribution ratio of polycyclic aromatic hydrocarbons in water bodies is analyzed to obtain the distribution ratio parameters; the distribution ratio parameters include dissolved phase, particulate adsorption phase and colloidal bound phase. Extracting a chemical information database of polycyclic aromatic hydrocarbons (PAHs); identifying the hydrophobicity constants and molecular size characteristics of PAHs with different ring numbers based on the PAH chemical information database; Based on the hydrophobicity constant and molecular size characteristics, the phase migration of water bodies is calculated using the allocation ratio parameters to obtain phase migration characteristics.

5. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 1, characterized in that, Step S3 is as follows: Define candidate enrichment methods; the candidate enrichment methods include liquid phase enrichment path, particle desorption path and composite enrichment path; Based on phase transition characteristics, data are input into candidate enrichment methods to calculate the expected recovery efficiency of the target material, the degree of potential matrix interference introduction, and the processing time cost of different candidate enrichment methods, thereby obtaining enrichment evaluation indicators. The optimal enrichment method for the current sample is determined based on enrichment evaluation indicators.

6. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 1, characterized in that, The specific steps of step S4 are as follows: Enrichment processing is performed based on the optimal enrichment method, and the enriched products are scanned and extracted. Identify and label interfering components in the enriched products; The coexistence risk of the interfering component with polycyclic aromatic hydrocarbons during co-elution or co-adsorption is calculated to obtain the risk assessment results; The purification plan is dynamically set based on the risk assessment results.

7. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 6, characterized in that, The purification scheme includes the combination of adsorption materials, the composition of the elution solvent, and the elution sequence.

8. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 1, characterized in that, The specific steps of step S5 are as follows: Based on the purification scheme, the test samples are pretreated and purified, and the solvent compatibility index, target concentration factor and baseline interference risk value are calculated by mass spectrometry. Based on the solvent compatibility index, target concentration factor, and baseline interference risk value, sample stability was assessed to obtain purification analysis results; Based on the purification analysis results, qualified samples are determined, and the pre-testing treatment is completed.

9. The sample pretreatment method for detecting polycyclic aromatic hydrocarbons in water according to claim 8, characterized in that, The specific steps for determining the suitability of samples based on the purification analysis results and completing the pre-testing treatment are as follows: The determination is made based on the purification analysis results and the preset detection reliability threshold. If the purification analysis results are not less than the preset detection reliability threshold, the sample is marked as qualified and the pre-detection processing is completed. If the purification analysis result is less than the preset detection reliability threshold, the sample is marked as unqualified and is removed from the test.

10. A sample pretreatment system for detecting polycyclic aromatic hydrocarbons in water, characterized in that, A sample pretreatment method for performing the detection of polycyclic aromatic hydrocarbons in water as described in claim 1 includes: The sample testing module performs matrix state detection on the tested samples to obtain a water body complexity feature set. The migration calculation module performs phase migration calculations of polycyclic aromatic hydrocarbons in water bodies based on the water body complexity feature set, and obtains phase migration characteristics. The enrichment method module determines the optimal enrichment method for the current sample based on phase transition characteristics; The enrichment processing module performs enrichment processing based on the optimal enrichment method to extract the enriched product; and sets a purification scheme based on the enriched product. The sample judgment module performs pretreatment purification on the test samples based on the purification scheme and judges whether the samples are qualified, thus completing the pretreatment operation for testing.

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