Method for detecting organic pollutants in liquid

Abstract

The invention discloses a method for detecting organic pollutants in liquid, which comprises the following steps: filtering liquid to be detected, mixing the filtered liquid with a metal ion chelating agent, and adjusting the pH value; adsorbing the liquid with the adjusted pH value by using a magnetic adsorption part coated with a selected adsorption phase to obtain the adsorbed magnetic adsorption part and the adsorbed liquid; eluting the magnetic adsorption part after adsorption to obtain an elution solution containing adsorption predetermined types of organic pollutants; carrying out low-temperature vacuum concentration on the adsorbed liquid to obtain a concentrated solution; combining the concentrated solution and an elution solution containing adsorbed predetermined types of organic pollutants, blow-drying and redissolving to obtain a redissolved solution; filtering the reconstitution fluid to obtain filtrate; and analyzing and detecting the filtrate to obtain the type and / or content of the organic pollutants contained in the liquid. According to the method, adsorption treatment and concentration treatment are combined, so that loss of heat sensitivity and volatile compounds is effectively avoided, and all-component analysis of organic pollutants in a sample is realized.

Description

Technical Field

[0001] The present invention relates to the field of analytical chemistry, in particular to a method for detecting organic pollutants in liquid. Background Art

[0002] There are many complex, emerging pollutants (NEPs) in the water environment, which have diverse chemical properties and concentration levels spanning multiple orders of magnitude. Existing targeted compound analysis methods, such as liquid-liquid extraction (LLE) and QuEChERS methods, have problems such as high solvent consumption and easy emulsification, and are not suitable for processing large volume samples. Advanced technologies such as solid phase extraction (SPE), supercritical fluid extraction (SFE), solid phase microextraction (SPME) and microwave-assisted extraction (MAE) have improved efficiency but lack versatility in dealing with pollutants with diverse chemical properties. Therefore, methods for comprehensive pollutant enrichment and chemical information retention in water samples need to be studied. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for detecting organic pollutants in liquid, which can achieve wide-range efficient extraction, enrichment and analytical detection of organic pollutants in water.

[0004] According to one aspect of the present invention, the present invention provides a method for detecting organic pollutants in a liquid. According to an embodiment of the present invention, the method includes: filtering the liquid to be tested, mixing it with a metal ion chelating agent, and adjusting it to a predetermined pH value to obtain a liquid after adjusting the pH value; using a magnetic adsorbent coated with a selected adsorption phase to adsorb the liquid after adjusting the pH value to adsorb a predetermined type of organic pollutants, and obtain an adsorbed magnetic adsorbent and an adsorbed liquid; eluting the adsorbed magnetic adsorbent to obtain an elution solution containing the adsorbed predetermined type of organic pollutants; performing a low-temperature vacuum concentration treatment on the adsorbed liquid to obtain a concentrated solution; combining the concentrated solution and the elution solution containing the adsorbed predetermined type of organic pollutants, blowing them dry and re-dissolving them to obtain a re-solution solution; filtering the re-solution solution to obtain a filtrate; and analyzing and detecting the filtrate to obtain the type and / or content of the organic pollutants contained in the liquid.

[0005] According to the method for detecting organic pollutants in liquids according to an embodiment of the present invention, adsorption treatment and concentration treatment are combined, which effectively avoids the thermal sensitivity and volatile compound loss of traditional methods and realizes the full component analysis of organic pollutants in samples. The method of the embodiment of the present invention is applicable to a wide range of compound categories, has high screening efficiency and detection sensitivity, and is suitable for liquid samples, especially the analysis of water samples of various environmental matrices.

[0006] In addition, the method for detecting organic pollutants in liquid according to the above embodiment of the present invention may also have the following additional technical features:

[0007] According to an embodiment of the present invention, the metal ion chelating agent is disodium ethylenediaminediacetic acid (Na2EDTA).

[0008] According to an embodiment of the present invention, the added amount of the metal ion chelating agent is 0.3-0.8% of the mass of the liquid.

[0009] According to an embodiment of the present invention, the predetermined pH value is pH 6.5-7.5.

[0010] According to an embodiment of the present invention, the selected adsorption phase comprises dimethylsiloxane (PDMS) and / or polydivinylbenzene (DVB).

[0011] According to an embodiment of the present invention, the predetermined type of organic pollutants is hydrophobic organic pollutants and thermosensitive organic pollutants.

[0012] According to an embodiment of the present invention, the temperature of the low-temperature vacuum concentration process is 45-65° C., and the rotation speed and pressure vary in a gradient.

[0013] According to an embodiment of the present invention, the gradient change conditions of the rotation speed and pressure are: -0 -1 hour: the rotation speed is 120r / min, the pressure is 150mbar; 1.0-1.1 hour: the rotation speed is 120-180r / min, the pressure is 150mbar; 1.1 hour-end: the rotation speed is 180r / min, the pressure is 120-80mbar.

[0014] According to an embodiment of the present invention, the volume of the concentrated solution is 0.5-2 mL.

[0015] According to an embodiment of the present invention, the elution process is performed using acetone.

[0016] According to an embodiment of the present invention, based on 100 mL of the liquid to be tested, the amount of acetone used in a single elution treatment is 0.8-1.2 mL.

[0017] According to an embodiment of the present invention, the elution treatment is performed 1-3 times.

[0018] According to an embodiment of the present invention, the re-dissolution is performed using the liquid to be tested.

[0019] According to an embodiment of the present invention, the volume of the reconstitution solution is 0.2-1 mL.

[0020] According to an embodiment of the present invention, the filtration process includes: dividing the complex solution into two parts on average to obtain a first complex solution and a second complex solution; filtering the first complex solution using a hydrophilic polypropylene (GHP) filter membrane to obtain a first filtrate; filtering the second complex solution using a polypropylene (PP) filter membrane to obtain a second filtrate; and combining the first filtrate and the second filtrate to obtain the filtrate.

[0021] According to an embodiment of the present invention, the analysis and detection is performed using liquid chromatography tandem mass spectrometry, preferably liquid chromatography tandem triple quadrupole mass spectrometry or liquid chromatography-high resolution mass spectrometry.

[0022] According to an embodiment of the present invention, the liquid to be tested is water, and the organic pollutants contained therein have a broad polarity of LogKow-8.1 to 11.6 and a broad content range of 1 pg / L-99 μg / L.

[0023] According to an embodiment of the present invention, the volume of the liquid to be tested is 100-300 mL.

[0024] According to an embodiment of the present invention, the magnetic adsorption component is a magnetic stirring bar.

[0025] According to an embodiment of the present invention, the coating thickness of the adsorption phase of the magnetic stirring bar is 0.5-2 mm, and the length is 20-60 mm.

[0026] According to an embodiment of the present invention, the particle size of the magnetic adsorption material is 20 μm-100 μm.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0029] Figure 1 A schematic diagram showing the recovery rates (N=3) of 67 standard compounds under different vacuum concentration conditions according to one embodiment of the present invention is shown;

[0030] Figure 2 A schematic diagram showing the recovery results (N=3) of 67 standard compounds under different pretreatment methods according to one embodiment of the present invention is shown;

[0031] Figure 3 A schematic diagram showing the number of detected peaks and characteristic distribution results of different pre-processing methods according to an embodiment of the present invention is shown;

[0032] Figure 4 A schematic diagram of the workflow of the MSE-LTVC pre-processing method according to an embodiment of the present invention is shown.

[0033] Figure 5 A schematic diagram showing the recovery rates (N=3) of 67 compounds in ultrapure water, surface water and groundwater according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0036] According to one aspect of the present invention, the present invention provides a method for detecting organic pollutants in liquids. The method for detecting organic pollutants in liquids according to an embodiment of the present invention combines adsorption treatment and concentration treatment, effectively avoiding the loss of heat sensitivity and volatile compounds in traditional methods, and realizing full component analysis of organic pollutants in samples. The method of the embodiment of the present invention is applicable to a wide range of compound categories, has high screening efficiency and detection sensitivity, and is applicable to liquid samples, especially the analysis of water samples of various environmental matrices.

[0037] In order to facilitate understanding of the method for detecting organic pollutants in liquid according to an embodiment of the present invention, the method is explained here. According to an embodiment of the present invention, the method includes:

[0038] S100 Chelation Treatment

[0039] According to an embodiment of the present invention, the liquid to be tested is filtered and then mixed with a metal ion chelating agent, and adjusted to a predetermined pH value to obtain a liquid after adjusting the pH value. Thus, the metal ion chelating agent combines with the metal ions in the liquid to be tested, and releases the chemical components originally combined with the metal ions. This process prevents the metal ions from further reacting with other chemical components, avoids possible interference, and thus ensures the accuracy of the analysis results. Through chelation, the metal ions are selectively fixed in the solution, which improves the stability of the liquid sample and the reliability of the analysis.

[0040] According to an embodiment of the present invention, the metal ion chelator is disodium ethylenediaminediacetic acid (Na2EDTA). As a metal ion chelator, Na2EDTA has the following advantages: (1) Broad-spectrum chelating ability: Na2EDTA can effectively chelate a variety of metal ions, including common divalent and trivalent metal ions such as calcium, magnesium, iron, and copper. This wide range of chelating ability ensures that it can capture a variety of potentially interfering metal ions in the liquid to be tested and prevent them from reacting with other chemical components; (2) High stability: The chelate formed by Na2EDTA and metal ions is extremely stable, which prevents the chelated metal ions from further reacting with other components in the liquid, ensuring the accuracy of the experimental results and the stability of the sample; (3) Solubility and adaptability: Na2EDTA has good solubility in water and is suitable for a wide pH range; (4) Biocompatibility and safety: Na2EDTA is a chelator commonly used in analytical chemistry and industrial applications, with high safety and biocompatibility. It will not cause damage to samples or equipment during routine experiments and processing, and is suitable for a wide range of experimental conditions. Therefore, using Na2EDTA as a metal ion chelating agent is beneficial to fully combine with the metal ions in the liquid to be tested and remove the interference of metal ions.

[0041] According to an embodiment of the present invention, the amount of the metal ion chelating agent added is 0.3-0.8% of the mass of the liquid. Adding the chelating agent in the above ratio has the following advantages: (1) Balance of chelation efficiency: This dosage range can ensure that sufficient Na2EDTA can effectively chelate with the metal ions in the liquid, avoiding the interference of metal ion residues in the analysis results caused by insufficient chelating agent. At the same time, this ratio avoids excessive use of chelating agent and reduces unnecessary interference or side effects that may be caused by excessive chelating agent; (2) Solution stability: Under this dosage, Na2EDTA can maintain good solubility in the solution, is not easy to form precipitation or affect the stability of the liquid, and ensures the smooth progress of the chelation reaction; (3) Ensure the accuracy of the analysis: This dosage can ensure that the chelating agent fully captures the metal ions in the liquid and prevents the metal ions from reacting with other components, while not generating background interference that may be introduced by excessive chelating agent, ensuring the accuracy and reliability of the analysis results.

[0042] According to an embodiment of the present invention, the predetermined pH value is pH 6.5-7.5. Setting the pH value to the above range has the following advantages: (1) Reducing the interference of pH differences between samples: If different samples have inconsistent pH values, it may affect the binding efficiency of the chelating agent and the metal ions, thereby causing deviation or inconsistency in the experimental results. By uniformly adjusting the pH values ​​of all samples to the range of 6.5 to 7.5, the interference caused by pH differences between samples can be effectively eliminated, ensuring that the chelation reaction is carried out under the same chemical environment, thereby improving the repeatability of the experiment and the accuracy of the results. This practice is widely used in analytical chemistry to control variables in the sample processing process and ensure that different samples are compared and analyzed under the same conditions; (2) Sample stability: Within this pH range, liquid samples generally have better chemical stability. Extreme pH conditions may cause degradation of components in the sample or produce adverse side reactions, while the pH range of 6.5 to 7.5 can minimize these problems, maintaining sample stability and the reliability of analytical results. (3) Preventing metal ion precipitation: In the pH range of 6.5-7.5, many common metal ions (such as calcium, magnesium, zinc, etc.) will not easily precipitate and can remain in the solution for chelation, ensuring that the chelating agent reacts fully with the metal ions and improving the removal efficiency of metal ions.

[0043] According to an embodiment of the present invention, the liquid to be tested is water, and the organic pollutants contained therein have a wide polarity of LogKow-8.1 to 11.6 and a wide content range of 1 pg / L-99 μg / L. Therefore, the present invention covers a wide range of organic substances and can comprehensively detect organic pollutants contained in water.

[0044] According to an embodiment of the present invention, the volume of the liquid to be tested is 100-300mL. Therefore, on the one hand, this volume of the liquid to be tested is suitable for enrichment of trace chemical components: since many target chemical components in the water body exist in trace concentrations, the main goal of the pre-treatment is to enrich these trace components. The sample volume of 100-300mL can provide sufficient starting amount for trace components during the sample enrichment process, effectively improve the detection concentration of these components in subsequent analysis, thereby enhancing the sensitivity and accuracy of the analytical instrument; on the other hand, this volume of the liquid to be tested can ensure the balance of the enrichment effect: selecting a sample volume of 100-300mL can provide sufficient sample base for pre-treatment, so that the target component reaches a detectable level after enrichment, and at the same time, the enrichment step will not be too long due to the large sample volume, affecting the efficiency of the experiment.

[0045] S200 adsorption treatment

[0046] According to an embodiment of the present invention, the liquid after adjusting the pH value is subjected to adsorption treatment by using a magnetic adsorbent coated with a selected adsorption phase to adsorb a predetermined type of organic pollutant, thereby obtaining an adsorbed magnetic adsorbent and an adsorbed liquid. Thus, the organic pollutants that are easily damaged during the low-temperature vacuum concentration process are adsorbed by the magnetic adsorbent, thereby achieving comprehensive enrichment of the organic pollutants in the liquid.

[0047] According to an embodiment of the present invention, the selected adsorption phase includes dimethylsiloxane (PDMS) and / or polydivinylbenzene (DVB). Therefore, the above compounds as the adsorption phase have the following advantages: (1) Efficient adsorption of hydrophobic organic pollutants: PDMS and DVB are both hydrophobic adsorption materials that can strongly interact with hydrophobic organic pollutants; hydrophobic organic pollutants are often difficult to be effectively captured by traditional enrichment methods in water bodies, and the high hydrophobicity of PDMS and DVB enables them to efficiently enrich such organic pollutants, ensuring that sufficient concentrations are obtained for detection in subsequent analysis; (2) High temperature resistance and chemical stability: PDMS and DVB both have good temperature resistance and chemical stability, and can maintain the integrity and adsorption capacity of the material during magnetic stirring operations. For heat-sensitive organic pollutants, these adsorption materials can avoid the degradation or loss of pollutants, ensuring Ensure the accuracy of analysis; (3) Suitable for enrichment of various types of organic pollutants: The porous structure and different adsorption characteristics of PDMS and DVB enable them to adsorb various types of organic pollutants, especially hydrophobic organic pollutants. The use of the above-mentioned multifunctional adsorption materials can capture multiple types of pollutants in one enrichment, achieve comprehensive enrichment of samples, and improve the breadth and efficiency of analysis; (4) Enhanced magnetic adsorption capacity: For hydrophobic and heat-sensitive organic pollutants, the use of magnetic adsorbents is combined. The enrichment efficiency is further enhanced by combining the adsorption material with magnetic particles. The use of magnetic adsorbents can quickly and effectively recover the adsorbed organic pollutants, reducing the operating steps of traditional adsorption materials and improving the efficiency and recovery rate of pretreatment.

[0048] The inventor has found that the use of low-temperature vacuum concentration treatment is prone to cause the loss of some organic pollutants. According to the method of the embodiment of the present invention, the inventor has studied the organic pollutants that are easily lost during the low-temperature vacuum concentration treatment. The inventor has analyzed these organic pollutants and found that they are hydrophobic organic pollutants and heat-sensitive organic pollutants. Then, for this type of specific pollutants, a magnetic adsorption device is used. Furthermore, according to an embodiment of the present invention, the predetermined type of organic pollutants is hydrophobic organic pollutants and heat-sensitive organic pollutants. Thus, the magnetic adsorption device is used to adsorb this type of organic pollutants that are easily damaged during the low-temperature vacuum concentration treatment, thereby achieving comprehensive enrichment of organic pollutants in the liquid.

[0049] S300 elution treatment

[0050] According to an embodiment of the present invention, the magnetic adsorbent is subjected to an elution treatment after adsorption, so as to obtain an elution solution containing the predetermined type of organic pollutants adsorbed. The organic pollutants adsorbed by the magnetic adsorbent are obtained through the elution treatment.

[0051] According to an embodiment of the present invention, acetone is used for the elution treatment. The elution treatment using acetone has the following advantages: (1) Excellent solubility: Acetone is an organic solvent with moderate polarity and good solubility, and can effectively dissolve various types of organic pollutants, especially hydrophobic and semi-polar compounds. Since the adsorption phase (such as PDMS and DVB) is mainly targeted at hydrophobic and thermosensitive organic pollutants, these pollutants may form strong hydrophobic interactions on the adsorption material, and acetone can effectively destroy such interactions, thereby eluting these pollutants from the adsorption phase, ensuring the complete recovery of the pollutants. (2) High volatility, easy for subsequent processing: The high volatility of acetone makes it very suitable for rapid concentration and processing of samples after elution. Acetone can efficiently dissolve organic pollutants adsorbed on the magnetic adsorbent during the elution process, and quickly evaporate in the subsequent drying step, without any residual interfering substances, ensuring the purity of the sample. This characteristic ensures that the concentrated target compounds can be quickly obtained after elution, which is convenient for subsequent analysis operations; (3) Suitable for a wide range of organic pollutant types: The chemical properties of acetone enable it to adapt to a variety of different types of organic pollutants. From polar to non-polar substances, acetone can be effectively eluted. Therefore, when analyzing a variety of organic pollutants in complex matrices such as water samples, acetone provides a wide range of applicability and can elute a variety of target compounds of different properties at one time, ensuring comprehensive pollutant recovery.

[0052] According to an embodiment of the present invention, based on 100 mL of the liquid to be tested, the amount of acetone used in a single elution treatment is 0.8-1.2 mL, which is conducive to sufficient elution of organic pollutants and avoids excessive total liquid volume caused by large amount of eluent.

[0053] According to an embodiment of the present invention, the number of times of the elution treatment is 1-3 times, thereby achieving a good elution effect.

[0054] According to an embodiment of the present invention, the magnetic adsorption member is a magnetic stirring bar, thereby achieving a good adsorption effect and facilitating solution stirring.

[0055] According to an embodiment of the present invention, the coating thickness of the adsorption phase of the magnetic stirring bar is 0.5-2 mm, and the length is 20-60 mm. Thus, the adsorption area is large and the adsorption capacity is high, which is conducive to fully adsorbing organic pollutants.

[0056] According to an embodiment of the present invention, the particle size of the magnetic adsorption material is 20μm-100μm. Therefore, the adsorption material in the above particle size range, on the one hand, has a high specific surface area, and increases the adsorption capacity: the magnetic adsorption material in the above particle size range has a high specific surface area, and the larger the specific surface area, the larger the area of ​​contact between the material and the organic pollutants in the liquid to be tested, thereby improving the adsorption capacity. A larger specific surface area means more adsorption sites, which can capture and fix more organic pollutants and improve the overall enrichment efficiency; on the other hand, the above particle size adsorption material is conducive to uniform dispersion: the magnetic adsorption material of the above particle size can ensure that it has good dispersibility in the liquid to be tested. Too large a particle size may cause the adsorption particles to settle and reduce the contact area with the pollutants, while too small a particle size may cause the particles to be too close, increase the resistance in the solution, and be unfavorable to the adsorption process.

[0057] S400 Low Temperature Vacuum Concentration Process

[0058] According to an embodiment of the present invention, the adsorbed liquid is subjected to low-temperature vacuum concentration to obtain a concentrated liquid, thereby enriching the main pollutants in the liquid through low-temperature vacuum concentration, and controlling the low-temperature concentration conditions to minimize the loss of organic pollutants.

[0059] According to an embodiment of the present invention, the temperature of the low-temperature vacuum concentration treatment is 45-65°C, and the rotation speed and pressure are gradient changes. Therefore, the above-mentioned low-temperature vacuum concentration treatment conditions can balance the concentration time and efficiency: the inventors have found that too low a temperature (such as 35°C) will significantly prolong the concentration time, resulting in inconvenient operation and low experimental efficiency. For example, it takes up to 9 hours to concentrate 200mL of water samples at 35°C, which is unrealistic for large-scale sample processing. Selecting a temperature range of 45-65°C can significantly shorten the concentration time and improve the processing efficiency of the experiment without increasing the operating burden, which is also conducive to the repeatability and controllability of the experiment; at the same time, the above-mentioned treatment conditions can reduce the loss of heat-sensitive compounds: too high a temperature will cause degradation or volatilization loss of heat-sensitive organic pollutants. The temperature range of 45-65°C is selected to ensure a faster concentration speed while avoiding the degradation and loss of organic pollutants as much as possible. Especially for some volatile or semi-volatile compounds, this temperature range can well balance efficient concentration and protection of pollutants, ensuring the effective recovery of various compounds in the sample.

[0060] According to an embodiment of the present invention, the gradient change conditions of the rotation speed and pressure are: 0-1 hour: the rotation speed is 120r / min, the pressure is 150mbar; 1.0-1.1 hours: the rotation speed is 120-180r / min, the pressure is 150mbar; 1.1 hours-end: the rotation speed is 180r / min, the pressure is 120-80mbar. The above-mentioned gradient change conditions of the rotation speed and pressure have the following advantages: (1) Progressive adjustment: The gradient change of the rotation speed and pressure is carried out gradually, ensuring a smooth transition during the concentration process and avoiding the influence of sudden temperature or pressure changes on the sample; (2) Preventing sample loss: The mild conditions in the initial stage and the gradually accelerated transition stage can minimize the excessive evaporation of the solvent or the sputtering of the sample, especially when the amount of liquid is large, to ensure that the organic pollutants in the sample will not be lost; (3) Flexible adaptation to different samples: This gradient adjustment is suitable for processing various types of liquid samples, especially for the enrichment of trace organic pollutants in water samples. Through the precise adjustment of the rotation speed and pressure, efficient and stable concentration processing can be performed for different samples.

[0061] According to an embodiment of the present invention, the volume of the concentrated solution is 0.5-2 mL, so that the volume is convenient for subsequent drying and re-dissolution.

[0062] S500 Blow dry and re-dissolve

[0063] According to an embodiment of the present invention, the concentrated solution and the elution solution containing the predetermined type of organic pollutants are combined and then blown dry and redissolved to obtain a reconstituted solution. Thus, the enriched solution to be tested is further concentrated by blowing dry and redissolving, and the predetermined solution to be tested is obtained, which is convenient for subsequent analysis and detection.

[0064] According to an embodiment of the present invention, the re-dissolution is performed using the liquid to be tested. Thus, by re-dissolving the original liquid to be tested, the organic pollutants lost during the adsorption treatment and low-temperature vacuum concentration treatment are added back into the liquid to be tested, so that the liquid to be tested can be enriched with the organic pollutants in the liquid to be tested as comprehensively as possible, thereby making the detection more accurate.

[0065] According to an embodiment of the present invention, the volume of the reconstitution solution is 0.2-1 mL, thereby facilitating subsequent analysis and detection.

[0066] S600 Filtration Process

[0067] According to an embodiment of the present invention, the reconstituted solution is filtered to obtain a filtrate, thereby removing impurities generated during the reconstitution process.

[0068] According to an embodiment of the present invention, the filtration process includes: dividing the reconstituted solution into two equal parts to obtain a first reconstituted solution and a second reconstituted solution; filtering the first reconstituted solution using a hydrophilic polypropylene (GHP) filter membrane to obtain a first filtrate; filtering the second reconstituted solution using a polypropylene (PP) filter membrane to obtain a second filtrate; and combining the first filtrate and the second filtrate to obtain the filtrate. Thus, the use of the above-mentioned filter membrane for filtration can be widely adapted to impurities of different properties: the combined use of the hydrophilic GHP filter membrane and the PP filter membrane can effectively deal with impurities of different properties. The GHP filter membrane has good hydrophilicity and is suitable for filtering water-soluble impurities in the reconstituted solution to ensure efficient filtration of hydrophilic pollutants, while the PP filter membrane has a wider range of chemical tolerance and can handle hydrophobic or insoluble impurities that may exist in the reconstituted solution; in addition, the GHP filter membrane and the PP filter membrane are used respectively, and each filter membrane is filtered according to different impurity characteristics to avoid the situation where a single filter membrane completely adsorbs pollutants, thereby improving the detection of pollutants, while ensuring the purity of the filtrate is conducive to subsequent analysis and detection. Therefore, the combined use of the two filter membranes can more comprehensively remove various impurities generated during the re-dissolution process, ensuring a high-purity filtrate.

[0069] S700 Analysis and Testing

[0070] According to an embodiment of the present invention, the filtrate is analyzed and tested to obtain the type and / or content of the organic pollutants contained in the liquid. Thus, the liquid to be tested obtained by the above method can be qualitatively or quantitatively tested for the organic pollutants in the liquid to be tested by different analytical testing methods.

[0071] According to an embodiment of the present invention, the analysis and detection is performed using liquid chromatography tandem mass spectrometry, preferably liquid chromatography tandem triple quadrupole mass spectrometry or liquid chromatography-high resolution mass spectrometry, thereby achieving high detection accuracy and sensitivity.

[0072] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention.

[0073] Below in conjunction with embodiment, the scheme of the present invention will be explained.It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.Unrepresented specific techniques or conditions in the embodiment, according to the technology or conditions described in the document in this area or according to the product specification sheet.Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, for example, can be purchased from Sigma company.

[0074] Example 1

[0075] In this embodiment, the parameters in the method for detecting organic pollutants in liquid are optimized as follows:

[0076] 1. Optimization of temperature and vacuum speed gradient during low temperature vacuum concentration (LTVC)

[0077] LTVC is a key pretreatment method that achieves effective enrichment of different types of compounds by controlling temperature and vacuum. This example investigates the recovery of 67 standard compounds at 35°C (A), 45°C (A), 55°C (A) and 55°C (B), and optimizes the concentration efficiency and recovery rate. The experimental conditions and results are detailed in Table 1 and Figure 1 .

[0078] Table 1 Gradient vacuum concentration conditions

[0079]

[0080] Note: (A) indicates vacuum concentration condition A, and (B) indicates vacuum concentration condition B. About 9.5, about 6, about 3.5, and about 4.5 respectively indicate the total time required to concentrate 200 mL of water sample to near dryness (about 0.5 mL) under the corresponding conditions.

[0081] Temperature setting: Under the same vacuum condition (A), the time required to concentrate 200mL of water sample to 0.5mL at 35℃, 45℃ and 55℃ were 9.5 hours, 6 hours and 3.5 hours respectively. The concentration speed was significantly accelerated at higher temperatures, but the loss of highly volatile and heat-sensitive compounds was also relatively large. Under 55℃ (A) conditions, the average recovery rate of 67 compounds was only 50.3%, while the average recovery rates at 35℃ and 45℃ were 63.7% and 55.6%, respectively.

[0082] Vacuum gradient adjustment: Under 55°C (B), the system pressure is lower, which further reduces the boiling point of the solvent and significantly increases the average recovery rate to 69.1%. This shows that by reducing the system pressure, the loss of volatile compounds under high temperature conditions can be effectively reduced, allowing more compounds to be enriched. At this time, the recovery rates of 6 standard compounds are less than 5%, the recovery rates of 12 compounds are between 10%-50%, the recovery rates of 14 compounds are between 50%-75%, and the recovery rates of 35 compounds are between 75%-116%.

[0083] The above results show that by optimizing the temperature and vacuum gradient, LTVC at 55°C (B) shows the best recovery rate and concentration efficiency. Under the combination of higher temperature and low vacuum, the concentration rate is guaranteed and the loss of highly volatile compounds is reduced. Nevertheless, a small number of compounds are still seriously lost when using only the LTVC method.

[0084] 2. Comparison of adsorption phases on the surface of magnetic stirring bars

[0085] In this experiment, the efficiency of water sample enrichment depends largely on the adsorbent material coated on the magnetic stirring bar. In order to optimize the recovery of compounds with different physicochemical properties, four adsorbent materials were compared, including polyaryletherketone (PPESK), polydimethylsiloxane (PDMS) PDMS / DVB, activated carbon / polydimethylsiloxane (ACAR / PDMS), and polydimethylsiloxane / polydivinylbenzene (PDMS / DVB). Their extraction efficiencies for 67 standard compounds were analyzed. The experimental results are detailed in Figure 2 , the information of 67 standard compounds is shown in Table 2.

[0086] PPESK material: PPESK has a high polarity and is suitable for adsorbing highly polar compounds. Experimental data show that the average recovery rate of PPESK for highly polar compounds with a retention time of less than 11 minutes is 7.2%, while the recovery rate for hydrophobic compounds with a retention time of more than 11 minutes is lower, averaging 9.2%.

[0087] PDMS / DVB, ACAR / PDMS and PDMS materials: All three materials contain PDMS and are suitable for the enrichment of moderately polar to hydrophobic compounds. The data show that the recoveries of hydrophobic compounds with retention times greater than 11 minutes under these three materials are 16.3%, 18.5% and 29.8%, respectively, while the recoveries of compounds with retention times less than 11 minutes are relatively low, ranging from only 2.7% to 4.4%, especially for PDMS materials, which have a recovery rate of more than 25% for hydrophobic compounds such as di-n-octyl phthalate (DNOP), tri-p-tolyl phosphate (TMPP) and ritonavir.

[0088] The above results show that the selection of different adsorption phases has a significant effect on the recovery rate of compounds with different properties. PDMS-based materials show better enrichment effects on hydrophobic compounds, while PPESK materials have a certain selectivity for highly polar compounds. Taking all factors into consideration, PDMS and PDMS / DVB are suitable for enriching highly hydrophobic pollutants, while PPESK can be used to increase the recovery of polar compounds.

[0089] 3. Optimization of parallel magnetic stirring extraction and low temperature vacuum concentration (MSE-LTVC)

[0090] In order to further improve the enrichment efficiency of water samples, the experiment combined magnetic stirring extraction (MSE) and LTVC method under 55°C (B) conditions to obtain MSE-LTVC pretreatment technology. This method fully utilizes the advantages of both MSE and LTVC to improve the recovery rate and detection sensitivity of a wide range of polar pollutants. Experimental data showed that the LTVC method mainly enriched medium-to-high polarity and low molecular weight compounds with a retention time of 1-15 minutes and a mass-to-charge ratio (m / z) of 100-800Da, and the MSE method mainly enriched compounds with a retention time of 12-18 minutes, depending on the characteristics of the adsorption material. Compared with a single pretreatment method, the combined treatment showed more compound signals (see Figure 3 ), indicating that combined processing may provide more comprehensive compound coverage or higher sensitivity. For example, the MSE-LTVC combined method achieved the detection of 10,164 mass spectral peaks, which is much higher than the single LTVC (9,384 peaks) and MSE methods (PDMS: 4,444 peaks). This method can simultaneously enrich pollutants of various physical and chemical properties, significantly improving the detection throughput and sensitivity of water samples, and is suitable for the analysis of multiple types of pollutants in complex matrices.

[0091] Example 2

[0092] According to the method for detecting organic pollutants in liquids according to an embodiment of the present invention, water samples collected from urban areas of Guilin are tested and analyzed. The detection process is as follows: Figure 4 As shown, it mainly includes four steps: sample pretreatment, magnetic stirring extraction, low-temperature vacuum concentration and small volume sample re-dissolution. The detection method implemented in this embodiment takes about 10 hours to process 16 samples for the first time. When batch processing samples, by parallelizing some steps, such as performing LTVC on the previous batch of samples (about 4.5 hours), the next batch of samples can be pretreated and MSE operated. Finally, it takes about 6 hours to process each 16 samples. The specific process is as follows:

[0093] (1) Sample pretreatment

[0094] 200 mL of water sample was filtered through a 0.45 μm aqueous phase filter membrane to remove suspended particles and macromolecular impurities; 0.7 g of disodium ethylenediaminediacetate (Na2EDTA) was added to the sample, and the pH of the sample solution was adjusted to 6.7 with 6 mmol / L HCl and NaOH.

[0095] (2) Magnetic stirring extraction (MSE)

[0096] 200mL of pretreated water sample was placed in a 500mL glass beaker, and a PDMS stirring rod with an extraction layer length of 20mm and thickness of 1mm was added; the beaker was placed on a magnetic stirrer, and the speed was set at 400r / min for 30min. The stirring rod was removed and placed in a 15mL centrifuge tube, 2mL of acetone was added, and ultrasonication was performed for 10min to decompose the adsorbed pollutants. The decomposition was repeated twice, and the decomposition solution was combined.

[0097] (3) Low Temperature Vacuum Concentration (LTVC)

[0098] The water sample treated with a magnetic stirring bar was placed in a vacuum parallel concentrator, the temperature was set to 55°C, and the speed and pressure gradient change conditions were: 0-1 hour: speed 120r / min, pressure 150mbar; 1.0-1.1 hours: speed 120-180r / min, pressure 150-120mbar; 1.1 hours-end: speed 180r / min, pressure 120-80mbar. When the sample was concentrated to a nearly dry state (about 0.5mL remaining), the sample was removed from the vacuum parallel concentrator and allowed to stand for 5-10 minutes to cool to room temperature.

[0099] Then, 4 mL of acetone solution obtained during the MSE process was combined and ultrasonicated for 2 min.

[0100] (3) Reconstitution of small volume samples

[0101] 4 mL of acetone analytical solution was purged with nitrogen at room temperature until nearly dry, and then 180 μL of real water sample that had not been treated with MSE and LTVC was used to dissolve the residue and ultrasonically treated for 2 minutes. The solution was filtered through a 0.22 μm filter membrane, and 20 μL of a mixed standard solution of 13 internal standards was added and vortexed for LC-HRMS / MS analysis.

[0102] (4) Specific detection methods for reconstitution of small volume samples

[0103] The experiment set up three groups of parallel samples, and the applicability of the pretreatment method in the analysis of different environmental water samples was verified by analyzing the test results of each group of samples. Figure 5As shown in Table 2, there are some differences in the recovery rates of different matrices. In ultrapure water, 97% of the standard compounds have a recovery rate between 25% and 150%, in surface water, 84% of the standard compounds have a recovery rate between 25% and 150%, and in groundwater, 90% of the standard compounds have a recovery rate between 25% and 150%. Through the retention time analysis of the standard compounds, it was found that the compounds with a recovery rate lower than 25% and higher than 150% in ultrapure water usually have lower polarity and a retention time greater than 12 minutes; in surface water and groundwater, these compounds include some compounds with higher polarity in addition to low-polarity compounds, indicating that their recovery rates may be affected by matrix interferences.

[0104] Table 2 Basic information of 67 compounds

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113] Note: The 67 compounds were subdivided into 10 chemical superclasses according to the classification rules of ClassyFire, and their polarity properties were determined by EPI Suite TM The oil-water partition coefficient (LogK ow )definition.

[0114] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0115] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for detecting organic pollutants in liquid, characterized in that: include: The liquid to be tested is filtered, mixed with a metal ion chelating agent, and adjusted to a predetermined pH value to obtain a liquid with adjusted pH value; Using a magnetic adsorbent coated with a selected adsorption phase to perform adsorption treatment on the liquid after adjusting the pH value, so as to adsorb a predetermined type of organic pollutants, and obtain an adsorbed magnetic adsorbent and an adsorbed liquid; The magnetic adsorbent is subjected to elution treatment after adsorption, so as to obtain an elution solution containing the adsorbed predetermined type of organic pollutants; The adsorbed liquid is subjected to low-temperature vacuum concentration treatment to obtain a concentrated liquid; The concentrated solution and the elution solution containing the adsorbed predetermined type of organic pollutants are combined, and then blown dry and redissolved to obtain a redissolved solution; filtering the complex solution to obtain a filtrate; as well as The filtrate is analyzed and tested to obtain the type and / or content of the organic pollutants contained in the liquid to be tested.

2. The method according to claim 1, characterized in that The metal ion chelating agent is disodium ethylenediaminediacetic acid, Optionally, the amount of the metal ion chelating agent added is 0.3-0.8% of the mass of the liquid. Optionally, the predetermined pH value is pH 6.5-7.

5.

3. The method according to claim 1, characterized in that The selected adsorption phase comprises dimethylsiloxane and / or polydivinylbenzene, Optionally, the predetermined type of organic pollutants is hydrophobic organic pollutants and thermosensitive organic pollutants.

4. The method according to claim 1, characterized in that: The temperature of the low-temperature vacuum concentration process is 45-65°C, and the speed and pressure are gradient changes; Optionally, the gradient change conditions of the rotation speed and pressure are: 0-1 hour: the rotation speed is 120r / min, the pressure is 150mbar; 1.0-1.1 hours: speed 120-180r / min, pressure 150-120mbar; 1.1 hour-end: speed 180r / min, pressure 120-80mbar; Optionally, the volume of the concentrate is 0.5-2 mL.

5. The method according to claim 1, characterized in that The elution treatment is carried out using acetone, Optionally, based on 100 mL of the liquid to be tested, the amount of acetone used in a single elution treatment is 0.8-1.2 mL, Optionally, the elution treatment is performed 1-3 times.

6. The method according to claim 1, characterized in that The re-dissolving is performed using the liquid to be tested, Optionally, the volume of the reconstitution solution is 0.2-1 mL.

7. The method according to claim 1, characterized in that The filtering process includes: Dividing the reconstituted solution into two equal parts to obtain a first reconstituted solution and a second reconstituted solution; Filtering the first complex solution using a hydrophilic polypropylene filter membrane to obtain a first filtrate; filtering the second complex solution using a polypropylene filter membrane to obtain a second filtrate; and The first filtrate and the second filtrate are combined to obtain the filtrate.

8. The method according to claim 1, characterized in that The analysis and detection is performed using liquid chromatography tandem mass spectrometry, preferably liquid chromatography tandem triple quadrupole mass spectrometry or liquid chromatography-high resolution mass spectrometry.

9. The method according to claim 1, characterized in that: The liquid to be tested is water, and the organic pollutants contained in it have a broad polarity of Log Kow-8.1 to 11.6 and a broad content range of 1 pg / L to 99 μg / L.

10. The method according to claim 1, characterized in that The volume of the liquid to be tested is 100-300mL, Optionally, the magnetic adsorption member is a magnetic stirring bar, Optionally, the coating thickness of the adsorption phase of the magnetic stirring bar is 0.5-2 mm, and the length is 20-60 mm, Optionally, the particle size of the magnetic adsorption material is 20 μm-100 μm.

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