A pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles

Abstract

This invention discloses a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances (PFAS) in complex matrix textiles, belonging to the field of materials analysis technology. The method involves placing the textile in an alkaline solvent containing an alkyl sulfonate displacing agent. Under heating conditions, the displacing agent utilizes its competitive adsorption mechanism to forcibly occupy matrix adsorption sites and displace the target analytes into the solvent. Subsequently, the temperature is rapidly lowered to the phase separation induction temperature, inducing supersaturation precipitation of the displacing agent, which then encapsulates impurities in situ and co-precipitates, forming a solid-liquid stratified system. Finally, the supernatant is collected for analysis. This invention utilizes the dual properties of the displacing agent—high-temperature solubilization and low-temperature phase change removal—to effectively break the strong adsorption equilibrium of aged textiles without using a solid-phase extraction column. This solves the contradiction between low extraction rate and significant matrix interference, significantly improving the recovery rate of PFAS. It offers advantages such as low cost, simple operation, and high accuracy.

Description

Technical Field

[0001] This invention relates to the field of materials analysis technology, and in particular to a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of organofluorine compounds with unique hydrophobic and oleophobic properties. Due to their excellent chemical stability and surface activity, they are widely used in waterproofing and oil-repellent finishing processes for textiles, apparel, outdoor equipment, and special protective products. However, studies have shown that PFAS are persistent, bioaccumulative, and potentially biotoxic, earning them the title of "permanent chemicals." With increasingly stringent global environmental regulations, such as the EU REACH and POPs regulations, the control requirements for PFAS in textiles have reached trace levels, posing a significant challenge to the sensitivity and accuracy of detection technologies. Because textile matrices are complex, typically containing various interfering components such as dyes, auxiliaries, and oligomers, and because the target substances often exist in trace amounts deep within the fibers or coatings, efficient pretreatment technologies are crucial for accurate detection.

[0003] Currently, the industry primarily refers to standard methods such as EN 17681-1 for the detection of PFAS in textiles. The core pretreatment process typically employs liquid-solid extraction, which uses alkaline organic solvents such as methanol to extract shredded textile samples under heating or ultrasonic-assisted conditions. The extract is then filtered or centrifuged before instrumental analysis. This method relies mainly on the solvent's dissolving power to disrupt the coating structure on the textile surface, thereby releasing the target substance into the solution.

[0004] However, in practical applications, the aforementioned standard pretreatment methods have significant limitations. First, PFAS, as a typical class of fluorinated surfactants, possess extremely strong interfacial adsorption properties. They readily and firmly adsorb onto the surface of textile fibers, the interior of porous structures, and the walls of extraction containers. Simply relying on the dissolving effect of solvents often fails to completely disrupt this adsorption-desorption equilibrium at the solid-liquid interface. This is especially true for complex textiles with severe aging, dense coatings, or large fiber surface areas, where solvents struggle to penetrate to the adsorption sites, leading to incomplete extraction of the target analyte and potentially causing false negatives in the test results.

[0005] Secondly, existing alkaline extraction systems lack selectivity. While dissolving PFAS, they also dissolve a large number of co-extractants from the textile matrix, such as dye molecules, textile auxiliaries, oils, and fiber oligomers. These complex matrix components significantly increase the viscosity and color of the extract, creating a severe matrix effect. If such extracts are directly injected for analysis, these impurities will contaminate the liquid chromatography column and mass spectrometry ion source, leading to signal suppression or enhancement, severely affecting the accuracy of quantification. On the other hand, using traditional solid-phase extraction (SPE) columns for purification is not only cumbersome and time-consuming, but the high cost of consumables also limits its application in large-scale detection.

[0006] Therefore, there is an urgent need to develop a pretreatment method for PFAS detection of textiles that can effectively overcome interfacial adsorption equilibrium to improve the extraction rate and can also simply and efficiently remove matrix interference. Summary of the Invention

[0007] This invention overcomes the shortcomings of the prior art and provides a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles, comprising the following steps:

[0009] S1. Place the textile sample in an extraction container, add an alkaline extraction solvent containing a displacement agent, and perform shaking extraction under heating conditions to allow the displacement agent to occupy the matrix adsorption sites and displace perfluorinated and polyfluoroalkyl substances into the solvent, thereby obtaining a primary extract.

[0010] The replacement agent is selected from at least one of alkyl sulfonates or alkylbenzene sulfonates;

[0011] S2. The primary extract is rapidly cooled to a phase separation induction temperature of -12°C to -8°C and maintained for a predetermined time to induce the displacement agent to precipitate from the solvent in a supersaturated state, and adsorb and encapsulate the matrix impurities in the extract in situ to settle together, forming a solid-liquid stratified system.

[0012] S3. Take the upper clear liquid from the solid-liquid separation system, which is the enrichment liquid of the perfluorinated and polyfluoroalkyl substances to be tested.

[0013] In a preferred embodiment of the present invention, the displacement agent is a non-fluorinated surfactant, and the mass concentration of the displacement agent in the alkaline extraction solvent is 0.05%-0.5%.

[0014] The displacement agent has a mass concentration of 0.05%-0.5% in the alkaline extraction solvent.

[0015] In a preferred embodiment of the present invention, the hydrophobic carbon chain length of the displacement agent is C8-C12, and the displacement agent is preferably sodium octyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate or sodium dodecylbenzene sulfonate.

[0016] In a preferred embodiment of the present invention, the alkaline extraction solvent is a mixture of methanol and sodium hydroxide solution, or a mixture of acetonitrile and sodium hydroxide solution.

[0017] In a preferred embodiment of the present invention, in step S1, the temperature range of the heating conditions is 55℃-65℃, and the extraction time is 30min-60min.

[0018] In a preferred embodiment of the present invention, in step S2, the time for cooling the primary extract to the phase separation induction temperature is controlled within 5 min to 10 min, and the predetermined holding time is 15 min to 30 min.

[0019] After maintaining the predetermined time, centrifugation is performed while keeping the phase separation induction temperature to obtain the solid-liquid stratified system.

[0020] In a preferred embodiment of the present invention, in step S1, the volume ratio of the alkaline extraction solvent to the mass of the textile sample is 20:1 to 50:1.

[0021] In a preferred embodiment of the present invention, in step S2, a salting-out agent is added to the primary extract before cooling, wherein the salting-out agent is sodium chloride, magnesium sulfate or ammonium acetate.

[0022] In a preferred embodiment of the present invention, after the upper clarified liquid is aspirated in step S3, the method further includes:

[0023] pH adjustment steps: Add an acidic regulator to the upper clear liquid to adjust the pH value of the solution to 6.0-8.0.

[0024] In a preferred embodiment of the present invention, step S4 is further included: after filtering the enriched solution of the perfluorinated and polyfluoroalkyl substances to be tested through a microporous membrane, it is injected into a liquid chromatography-tandem mass spectrometer for qualitative and quantitative analysis.

[0025] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0026] This invention introduces a specific displacement agent into an alkaline extraction system and utilizes its molecular structural similarity to the target analyte to construct an active extraction mode based on a competitive adsorption mechanism. Due to the superior surface activity and specific hydrophobic carbon chain structure of the displacement agent molecules, under heating and shaking conditions, they can rapidly occupy high-energy adsorption sites on the surface of textile fibers and within micropores, thereby forcibly displacing and desorbing trace PFAS molecules that were originally strongly adsorbed onto the matrix by van der Waals forces or hydrogen bonds into the solvent phase. This active displacement mechanism fundamentally breaks through the adsorption-desorption equilibrium limitation of traditional solvent extraction methods that rely solely on solubility diffusion. It effectively solves the problem of incomplete extraction caused by insufficient solvent penetration in existing standard methods when detecting aged or densely coated fabrics, significantly improving the absolute recovery rate of the target analyte and ensuring the accuracy and reliability of trace detection results.

[0027] This invention utilizes the physicochemical property that the solubility of a displacement agent changes abruptly at different temperatures. By rapidly cooling the extract to a specific phase separation induction temperature range, a one-step in-situ purification is achieved. Under this low-temperature environment, the supersaturated precipitated displacement agent molecules undergo phase transition and precipitate. During the sedimentation process, through physical encapsulation and adsorption, they carry suspended dye molecules, waxes, oligomers, proteins, and other matrix interferences into the precipitate layer. This clarifies the extract without introducing additional solid-phase extraction materials, thus avoiding the cumbersome solid-phase extraction steps required in existing technologies to remove complex matrices. This significantly reduces detection costs and time, eliminates the risk of target analyte adsorption loss due to multi-step purification operations, and allows the treated sample to directly meet the injection requirements of liquid chromatography-tandem mass spectrometry, effectively extending the maintenance cycle of precision instruments.

[0028] This invention achieves synergistic coupling of high-temperature solubilization extraction and low-temperature phase change purification within the same reaction system through precise control of the phase separation temperature window and liquid-solid ratio parameters. The displacement agent acts as an extraction aid at high temperatures to enhance extraction efficiency, while transforming into a purification agent at low temperatures to clean the matrix. This temperature-dependent reversal characteristic allows the pretreatment process to be completed without transferring containers, greatly simplifying the operation. Compared to the traditional method where extraction and purification are independent and fragmented, the temperature-sensitive treatment system constructed in this invention ensures excellent purification effects on dark-colored and complex-component textiles while minimizing the use of organic solvents and human error. This provides a highly valuable industrial application path for the rapid, green, and standardized detection of PFAS in large quantities of textiles. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to the present invention. Detailed Implementation

[0031] 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.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0033] Application Overview:

[0034] In the field of textile chemical testing, especially for the detection of trace perfluorinated and polyfluoroalkyl substances, there has long been a fundamental contradiction between deep extraction and matrix interference. The mainstream treatment method in the current technology is the EN 17681-1 standard method, which mainly relies on the dissolving power of organic solvents for liquid-solid extraction. However, facing increasingly complex textile processes, especially textiles that have undergone durable waterproofing treatment, long-term aging, or contain complex dye systems, simple solvent extraction faces a dilemma: PFAS, as a powerful surfactant, tends to accumulate at high-energy sites on the fiber surface or be encapsulated within dense polymer coatings; for aged fabrics, this adsorption often transforms from physical adsorption to stronger chemical adsorption or pore trapping, while conventional solvents struggle to penetrate deep into the micropores, resulting in a bottleneck in the extraction rate and easily leading to severely low detection results. In addition, if more drastic extraction conditions are used to improve the extraction rate, a large amount of coexisting substances in the textile matrix will inevitably dissolve, such as disperse dyes, textile auxiliaries, oligomers, oils and waxes. After these impurities enter the extract, they will seriously contaminate the liquid chromatography column and produce strong ion suppression or enhancement effects at the mass spectrometry ion source, resulting in completely distorted quantitative results. To solve the above contradiction, the industry usually has to use solid phase extraction columns for multi-step purification. This not only increases the cost of single-sample testing, but also makes the operation cumbersome and time-consuming. More importantly, the solid phase extraction column itself also has irreversible adsorption of long-chain PFAS, making it impossible to simultaneously achieve the requirements of high extraction rate and high purity.

[0035] This invention pioneers a completely new technical route by organically combining two core technologies: in-situ competitive displacement and temperature-sensitive homogeneous demulsification.

[0036] This innovative approach introduces a non-fluorinated surfactant with a structure similar to PFAS as a displacement agent. During the high-temperature extraction stage, the higher molar concentration and surface activity of the displacement agent actively occupy adsorption sites on the fiber surface, squeezing trace amounts of PFAS from deep pores into the solvent phase, thus achieving deep extraction without damaging the matrix. Furthermore, this approach utilizes the physicochemical property of the displacement agent's abrupt solubility changes at different temperatures. After extraction, rapid cooling to a specific phase separation induction temperature range causes the dissolved displacement agent to instantly transform into a supersaturated state and precipitate. The precipitated microcrystals act as flocculants during sedimentation, encapsulating and adsorbing dyes and impurities in the solution, co-precipitating them, while the target PFAS, due to its unique fluorocarbon chain structure, remains in the supernatant. This invention achieves a closed-loop extraction and purification process within the same container by switching between high-temperature fluxing and low-temperature phase change purification. Compared with existing technologies, this method greatly improves the absolute recovery rate of PFAS in complex matrices while reducing matrix effects and significantly improving the accuracy, economy, and efficiency of detection, all without the need for expensive SPE columns.

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] like Figure 1 As shown, a pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles includes the following steps:

[0039] S1. Place the textile sample in an extraction container, add an alkaline extraction solvent containing a displacement agent, and perform shaking extraction under heating conditions to allow the displacement agent to occupy the matrix adsorption sites and displace perfluorinated and polyfluoroalkyl substances into the solvent, thereby obtaining a primary extract.

[0040] The replacement agent is selected from at least one of alkyl sulfonates or alkylbenzene sulfonates;

[0041] S2. The primary extract is rapidly cooled to a phase separation induction temperature of -12°C to -8°C and maintained for a predetermined time to induce the displacement agent to precipitate from the solvent in a supersaturated state, and adsorb and encapsulate the matrix impurities in the extract in situ to settle together, forming a solid-liquid stratified system.

[0042] S3. Take the upper clear liquid from the solid-liquid separation system, which is the enrichment liquid of the perfluorinated and polyfluoroalkyl substances to be tested.

[0043] In realizing the aforementioned displacement and purification concept, the inventors faced the primary technical challenge of introducing an auxiliary agent that could enhance extraction thermodynamics without interfering with subsequent mass spectrometry analysis. In conventional analytical chemistry, surfactants are typically considered interferences in mass spectrometry detection because they preferentially accumulate on droplet surfaces, hindering the evaporation and escape of target ions, leading to severe signal suppression. Therefore, the key to this approach is finding a substance that can act as a powerful extraction aid at high temperatures and can be automatically and completely removed from the solution before sample injection. This invention utilizes the thermodynamic property of alkyl sulfonates with specific chain lengths exhibiting steep solubility curves in a methanol-water system to successfully achieve a temporal switching of the displacement agent function. Another challenge is to prevent the unexpected loss of the target material during the removal of impurities, especially during the low-temperature precipitation of the displacement agent, it is essential to ensure that long-chain PFAS is not removed by co-precipitation. Since long-chain PFAS and the displacement agent are structurally similar, they are prone to mixed crystallization. This invention finds a delicate thermodynamic equilibrium point by precisely controlling the window of phase separation induction temperature and utilizing the difference in van der Waals radii between fluorine and hydrogen atoms in the PFAS molecule and the rigid structure of the perfluorinated chain. This allows the displacement agent to crystallize out while the PFAS remains dissolved due to the supercooled state.

[0044] Preferably, the extraction container in step S1 refers to a vessel used to hold the sample and solvent for reaction. In this embodiment, it specifically refers to a stoppered centrifuge tube made of polypropylene. Because PP material has moderate hydrophobicity and good alkali resistance, it is the best choice. Glass containers are strictly prohibited here because PFAS is easily adsorbed on the silanol groups on the glass surface, which will lead to serious adsorption loss.

[0045] Preferably, the displacement agent refers to an exogenous chemical substance that is intentionally introduced into the extraction system. In this invention, it is not only a surfactant but also a molecular probe. Its molecular structure typically includes a hydrophobic long chain tail and a hydrophilic head. In the S1 stage, it takes advantage of its high concentration to competitively insert into the micropores or coating defects on the fiber surface through van der Waals forces, thereby disrupting the binding force between PFAS and the matrix.

[0046] Preferably, the alkaline extraction solvent is a mixture of methanol and sodium hydroxide aqueous solution, with a volume ratio of methanol to sodium hydroxide aqueous solution of 3:1 to 5:1, and the molar concentration of the sodium hydroxide aqueous solution is 0.1 mol / L to 0.5 mol / L. Methanol provides the solubility for PFAS. The alkaline environment has a dual function: first, it hydrolyzes the oils and some ester bonds on the surface of the fabric, causing the fiber to swell; second, it completely converts PFAS molecules into ionic states, increasing their solubility in the solvent and reducing adsorption on the container wall.

[0047] Preferably, the heating condition in step S1 refers to raising the system temperature to a level significantly higher than room temperature, such as 55°C-65°C. The physical significance of heating is to provide activation energy, accelerate the Brownian motion of molecules, and allow the solvent and displacement agent to penetrate into the dense structure of the aged fabric more quickly. At the same time, high temperature will reduce the viscosity of the solvent and improve the mass transfer efficiency.

[0048] Preferably, oscillation extraction refers to applying mechanical energy while heating. Since simple static soaking cannot overcome the diffusion layer resistance at the solid-liquid interface, oscillation can continuously renew the solvent layer at the interface, maintain the maximum concentration difference, and thus improve the extraction kinetic rate.

[0049] Preferably, the rapid cooling in step S2 refers to the extraction liquid being cooled from 60°C to approximately -10°C within 5-10 minutes after extraction. The purpose of rapid cooling is to create deep supersaturation in the system, prompting the displacing agent to nucleate explosively, thereby forming a large number of fine microcrystals. Compared to the large crystals formed by slow cooling, microcrystals have a huge specific surface area and can adsorb impurities more efficiently.

[0050] Preferably, the phase separation induction temperature in step S2 is a specific thermodynamic state point at which the solvent system's ability to dissolve the displacing agent decreases by several orders of magnitude, forcing the displacing agent to undergo a phase change, i.e., from the liquid phase to the solid phase.

[0051] Preferably, in-situ adsorption and encapsulation is the core mechanism of this invention. The displacement agent crystals precipitated in this step are not pure substances, but rather a carrier. The hydrophobic impurities suspended in the solution act as seeds for heterogeneous nucleation, or are physically encapsulated by the growing crystals. At the same time, the charged displacement agent surface also removes some of the water-soluble dyes with opposite charges through electrostatic adsorption.

[0052] Preferably, the solid-liquid separation system refers to the process after step S2, where the originally homogeneous extract is separated into two layers under the action of gravity or centrifugal force: the lower layer is a solid precipitate layer or high-density flocculation layer containing displacement agent crystals and impurities, and the upper layer is a clear organic solvent layer rich in PFAS.

[0053] Preferably, most of the interfering substances have been removed from the enrichment solution of the perfluorinated and polyfluoroalkyl substances to be tested in step S3, and the PFAS concentration is accurately reflected due to the reduction of matrix effect. It can be directly used for LC-MS / MS analysis, or analyzed after simple pH adjustment.

[0054] In order to achieve a balance between high recovery rate and low matrix effect, the core parameters of this invention have been strictly defined.

[0055] Specifically, the replacement agent is an alkyl sulfonate with a hydrophobic carbon chain length of C8 to C12, such as sodium dodecyl sulfonate (SDS) or sodium dodecylbenzene sulfonate (SDBS).

[0056] In detail, the reason for choosing this carbon chain length lies in the conformational matching principle. The main carbon chain length of controlled PFAS target compounds, such as perfluorooctanoic acid (PFOA) or perfluorooctane sulfonic acid (PFOS), is usually around C8. According to the principle of like dissolves like and steric hindrance, alkyl sulfonates with similar chain lengths can best simulate the adsorption conformation of PFAS on the fiber surface, thereby displacing PFAS from the adsorption site through a molecular substitution mechanism. If the chain is too short, the surface activity is insufficient and the substitution ability is weak; if the chain is too long, precipitation is too thorough at low temperatures, and long-chain PFAS may be entrained due to the co-crystallization effect, resulting in a loss of recovery rate.

[0057] In detail, the reason for choosing sulfonates is that sulfonic acid groups are strong acid-strong base salts, which completely ionize in alkaline extracts to provide excellent water solubility, while their sodium salts have a high lattice energy in low-temperature organic phases and are easy to crystallize and precipitate. After experimental optimization, the mass concentration of the displacement agent in the alkaline extraction solvent should be controlled between 0.05% and 0.5%.

[0058] Specifically, the extraction temperature should be controlled between 55°C and 65°C to ensure sufficient activation energy to break physical adsorption.

[0059] Specifically, the phase separation induction temperature in step S2 is precisely limited to -12°C to -8°C; this is a counterintuitive narrow window selection, and the determination of this temperature range is based on dual constraints.

[0060] In detail, the upper limit constraint is -8°C. Experiments show that when the temperature is above -8°C, the solubility of sodium dodecyl sulfate in the methanol-water system is still high, resulting in incomplete precipitation, which leads to insufficient impurity removal rate and the residual replacement agent will interfere with subsequent detection.

[0061] In detail, the lower limit constraint is -12°C. When the temperature is below -12°C, long-chain PFAS that are originally highly soluble, such as perfluorotetradecanoic acid (PFTA) of the tetradecane group, begin to become unstable. Due to its similar structure to the displacement agent, it is very easy to co-precipitate, that is, it is accidentally damaged by the crystal and sinks to the bottom.

[0062] Therefore, only by precisely controlling the temperature within the range of -12°C to -8°C can the dual goals of extremely low residual amount of displacement agent and extremely high recovery rate of long-chain PFAS be achieved.

[0063] To verify the extraction and purification performance of this invention under different process conditions and to explore the critical effects of various parameter boundaries, several examples and comparative examples are provided below for detailed description. Unless otherwise specified in the following examples, all raw materials are commercially available or prepared using conventional methods in the art.

[0064] Example 1:

[0065] This embodiment is used to verify the extraction and purification performance of the present invention under optimal process conditions.

[0066] In step S1, 2.0 g of sample was placed in a 50 mL polypropylene centrifuge tube, and 40 mL of a methanol and sodium hydroxide mixed extraction solution containing 0.1% sodium dodecyl sulfonate was added. The volume ratio of methanol to 0.2 mol / L sodium hydroxide aqueous solution was 4:1. The mixture was extracted by shaking at 250 rpm in a 60°C constant temperature shaker for 40 minutes.

[0067] In step S2, the primary extract is directly inserted into a temperature-controlled cold trap at -10°C and frozen for 20 minutes to induce phase separation;

[0068] In step S3, the sample is centrifuged and the supernatant is aspirated while maintaining a low temperature. The pH is then adjusted to neutral before being injected for analysis.

[0069] Example 2:

[0070] This embodiment investigates the effect of the lower limit of the displacement agent concentration on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the amount of sodium dodecyl sulfonate added in step S1 is changed to a mass concentration of 0.05%.

[0071] Example 3:

[0072] This embodiment investigates the effect of the upper limit of the displacement agent concentration on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the amount of sodium dodecyl sulfonate added in step S1 is changed to a mass concentration of 0.5%.

[0073] Example 4:

[0074] This embodiment investigates the effect of the lower limit of the extraction temperature on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the heating conditions in step S1 are changed so that the extraction temperature is set to 55°C.

[0075] Example 5:

[0076] This embodiment investigates the effect of the upper limit of extraction temperature on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the heating conditions in step S1 are changed so that the extraction temperature is set to 65°C.

[0077] Example 6:

[0078] This embodiment investigates the effect of short-chain hydrophobic displacing agents on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the type of displacing agent used in step S1 is changed, replacing it with sodium octyl sulfonate, while maintaining the mass concentration at 0.1%.

[0079] Example 7:

[0080] This example investigates the effect of medium-carbon chain length displacing agents on extraction and purification performance. The preparation process is exactly the same as in Example 1, except that the type of displacing agent used in step S1 is changed, replacing it with sodium decyl sulfonate, while maintaining the mass concentration at 0.1%.

[0081] Example 8:

[0082] This example explores the feasibility of using sulfonates containing benzene ring structures as displacing agents. The preparation process is exactly the same as in Example 1, except that the type of displacing agent used in step S1 is changed, replacing it with sodium dodecylbenzenesulfonate, while maintaining the mass concentration at 0.1%.

[0083] Comparative Example 1:

[0084] This comparative example was used to investigate the effect of the absence of a displacement agent on extraction efficiency. The preparation process was exactly the same as in Example 1, except that in step S1, no displacement agent was added to the alkaline extraction solvent, i.e., the sodium dodecyl sulfate concentration was 0%, and extraction was performed using only a mixture of methanol and sodium hydroxide. Subsequent steps remained the same, but no obvious flocculent precipitate was observed during the cooling process in step S2.

[0085] Comparative Example 2:

[0086] This comparative example was used to investigate the necessity of the temperature-sensitive phase change purification step for eliminating the matrix effect. The preparation process was exactly the same as in Example 1, except that the cooling and freezing operation in step S2 was omitted. After extraction in step S1, no cooling was performed; instead, the extract was directly cooled to room temperature (25°C) before centrifugation and filtration, followed by instrumental analysis.

[0087] Comparative Example 3:

[0088] This comparative example was used to investigate the failure of nonionic surfactants as displacing agents. The preparation process was exactly the same as in Example 1, except that in step S1, the nonionic surfactant Tween 80 was used instead of sodium dodecyl sulfonate, and the mass concentration was kept at 0.1%.

[0089] Comparative Example 4:

[0090] This comparative example was used to investigate the effect of excessively low phase separation induction temperature on the recovery rate of long-chain target compounds. The preparation process was exactly the same as in Example 1, except that in step S2, the phase separation induction temperature was set to -25°C. The primary extract was frozen in a cryogenic environment at -25°C for 20 minutes, and then the supernatant was collected by centrifugation at low temperature.

[0091] Comparative Example 5:

[0092] This comparative example was used to investigate the effect of excessively low extraction temperature on extraction efficiency. The preparation process was exactly the same as in Example 1, except that in step S1, the extraction temperature under heating conditions was significantly reduced to 40°C.

[0093] Comparative Example 6:

[0094] This comparative example was used to investigate the effect of excessively high extraction temperature on matrix damage. The preparation process was exactly the same as in Example 1, except that in step S1, the extraction temperature under heating conditions was significantly increased and set to 80°C.

[0095] Comparative Example 7:

[0096] This comparative example was used to investigate the effect of excessively low concentration of the displacement agent on extraction efficiency. The preparation process was exactly the same as in Example 1, except that in step S1, the mass concentration of sodium dodecyl sulfonate was significantly reduced to 0.01%.

[0097] Comparative Example 8:

[0098] This comparative example was used to investigate the effect of excessively high displacement agent concentration on purification efficiency and liquid recovery rate. The preparation process was exactly the same as in Example 1, except that in step S1, the mass concentration of sodium dodecyl sulfonate was significantly increased to 1.0%.

[0099] Experimental testing and results analysis:

[0100] The enriched solutions obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were analyzed by liquid chromatography-tandem mass spectrometry to investigate the absolute recoveries, matrix effects (ME%), and column pressure changes of perfluorooctanoic acid (PFOA, C8) and perfluorotetradecanoic acid (PFTA, C14). The results are summarized in Table 1 below.

[0101] Table 1: Comparison of PFAS recovery rates and matrix effect data for different treatment methods

[0102]

[0103] Experimental results show that Examples 1 to 8 maintained a high recovery rate of over 90% for both perfluorooctanoic acid and perfluorotetradecanoic acid, and the matrix effect was effectively suppressed. The column pressure increment was within a safe range. In contrast, the data from the comparative examples revealed the serious consequences of deviating from the core parameters of this invention.

[0104] Comparative Examples 1 and 7 demonstrate the importance of the displacing agent and its concentration. When no displacing agent is added or the concentration is extremely low, the strong adsorption equilibrium of the aged fabric cannot be broken due to the lack of sufficient competitive displacement motive force, resulting in a significant decrease in extraction rate. Conversely, Comparative Example 8 shows that an excessively high concentration of displacing agent will result in an excessively large volume of precipitate at low temperatures, which not only retains a large amount of supernatant, causing a decrease in liquid recovery rate, but also causes a serious matrix effect due to residual surfactant.

[0105] Comparative Examples 5 and 6 reveal the boundary effect of extraction temperature. When the temperature is as low as 40°C, it fails to provide sufficient activation energy, and the insufficient solvent penetration leads to incomplete extraction. When the temperature is as high as 80°C, it causes the solvent to boil and evaporate, resulting in the complete destruction of the matrix. A large amount of impurities dissolve out, causing the subsequent purification steps to fail.

[0106] Comparative Examples 2 and 4 verified the core function of temperature-sensitive phase change purification. Failure to cool and freeze would lead to direct instrument blockage, while excessive cooling to -25°C, although effective in removing impurities, resulted in severe co-precipitation of long-chain perfluorotetradecanoic acid with the displacing agent, causing the recovery rate to plummet to 61.5%. Comparative Example 3 showed extremely poor performance after using a nonionic surfactant, demonstrating that only sulfonates with specific crystallization characteristics can achieve the in-situ encapsulation and sedimentation objective of this invention.

[0107] In summary, this invention addresses the dual challenges of incomplete extraction and severe matrix interference faced by existing technologies in detecting perfluorinated and polyfluoroalkyl substances in complex matrix textiles. By introducing alkyl sulfonates with specific structures as displacement agents and cleverly utilizing their solubility differences at different temperatures, a synergistic treatment system of high-temperature competitive displacement and low-temperature phase transition homogeneous demulsification is constructed. This system not only effectively breaks the strong adsorption equilibrium of target substances on aged fabrics, achieving deep extraction, but also utilizes the phase transition crystallization of the displacement agent to capture impurities in situ, achieving efficient purification without the need for a solid-phase extraction column. In particular, by precisely controlling the concentration boundary, extraction temperature boundary, and the critical temperature window of -12°C to -8°C, the problem of co-precipitation loss of long-chain target substances is successfully solved. Ultimately, a perfect balance of high recovery rate, low matrix effect, and low cost is achieved, providing an innovative solution with significant industrial application value for the accurate detection of trace perfluorinated and polyfluoroalkyl substances in textiles.

[0108] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles, characterized in that, Includes the following steps: S1. Place the textile sample in an extraction container, add an alkaline extraction solvent containing a displacement agent, and perform shaking extraction under heating conditions to allow the displacement agent to occupy the matrix adsorption sites and displace perfluorinated and polyfluoroalkyl substances into the solvent, thereby obtaining a primary extract. The replacement agent is selected from at least one of alkyl sulfonates or alkylbenzene sulfonates; S2. The primary extract is rapidly cooled to a phase separation induction temperature of -12°C to -8°C and maintained for a predetermined time to induce the displacement agent to precipitate from the solvent in a supersaturated state, and adsorb and encapsulate the matrix impurities in the extract in situ to settle together, forming a solid-liquid stratified system. S3. Take the upper clear liquid from the solid-liquid separation system, which is the enrichment liquid of the perfluorinated and polyfluoroalkyl substances to be tested.

2. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, The displacement agent has a mass concentration of 0.05%-0.5% in the alkaline extraction solvent.

3. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 2, characterized in that, The replacement agent is sodium octyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate, or sodium dodecylbenzene sulfonate.

4. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, The alkaline extraction solvent is a mixture of methanol and sodium hydroxide solution, or a mixture of acetonitrile and sodium hydroxide solution.

5. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, In step S1, the temperature range of the heating conditions is 55℃-65℃, and the extraction time is 30min-60min.

6. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, In step S2, the time for cooling the primary extract to the phase separation induction temperature is controlled within 5 min to 10 min, and the predetermined maintenance time is 15 min to 30 min. After maintaining the predetermined time, centrifugation is performed while keeping the phase separation induction temperature to obtain the solid-liquid stratified system.

7. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, In step S1, the volume ratio of the alkaline extraction solvent to the mass of the textile sample is 20:1 to 50:

1.

8. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, In step S2, a salting-out agent, such as sodium chloride, magnesium sulfate, or ammonium acetate, is added to the primary extract before cooling.

9. The pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to claim 1, characterized in that, After step S3, which involves aspirating the upper clarified liquid, the process further includes: pH adjustment steps: Add an acidic regulator to the upper clear liquid to adjust the pH value of the solution to 6.0-8.

0.

10. A pretreatment method for detecting trace perfluorinated and polyfluoroalkyl substances in complex matrix textiles according to any one of claims 1 to 9, characterized in that, The method also includes step S4: after filtering the enriched solution of the perfluorinated and polyfluoroalkyl substances to be tested through a microporous membrane, it is injected into a liquid chromatography-tandem mass spectrometer for qualitative and quantitative analysis.

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