A method for measuring polybrominated diphenyl ether substances

Abstract

The application discloses a kind of polybrominated diphenyl ether class substance determination methods, utilize DGT device determination environmental medium (water body, soil and sediment) polybrominated diphenyl ether class substance, with the modified multi-walled carbon nanotube of 0.5-2 microns length of particle size, about 50nm diameter modified carbon nanotube adsorption film is prepared to agarose membrane, the adsorption film is applied to gradient diffusion film (DGT) technology based on, and suitable shell device, diffusion membrane, filter membrane are selected;After adsorption is completed, suitable eluent is selected, and the determination error of polybrominated diphenyl ether class substance is maximized to eliminate;The application preparation process is simple, time is short, determination and subsequent processing procedure is simple and convenient, suitable for in-situ detection of polybrominated diphenyl ether class substance in water body.

Description

Technical Field

[0001] This invention relates to the field of gradient diffusion thin film technology, and more specifically, to a method for determining polybrominated diphenyl ethers. Background Technology

[0002] Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants in textiles and plastic products. Due to their high efficiency in escaping from products into the environment, PBDE levels in the environment have been increasing year by year in recent years. PBDEs are now widely detected in the atmosphere, water, soil, sediment, animal and plant matter, and human blood and milk (Strandberg, B. Dodder, NG, et al. Environmental Science & Technology, 2001, 35(6):1078-1083; Akutsu, K., Obana, H., et al., Chemosphere, 2001, 44:1325-1333). In the soil and water of electronic waste dismantling areas, PBDE pollution is even more severe. PBDEs are very stable in the environment and are persistent environmental pollutants of global concern. Due to their strong lipophilicity, PBDEs are very easy to accumulate through the food chain and exhibit bioaccumulation. There are many homologues of PBDEs, but the most commonly used PBDEs in industry are pentabromodiphenyl ether, octabromodiphenyl ether, and decabromodiphenyl ether. Although PBDEs have low acute toxicity, studies have shown that their chronic toxicity mainly affects organs such as the liver, kidneys, and thyroid. Moreover, a large number of experimental results show that PBDEs have endocrine-disrupting effects, reproductive toxicity, hepatotoxicity, neurotoxicity, immunotoxicity, and developmental toxicity (Renzelli, V., Gallo, M., et al. Cancers (Basel), 2023, 15(17): 4237; Xue, JS, Xiao, QP, et al., International Journal of Molecular Sciences, 2023, 24(17): 13487; Chen, JC, Baumert BO, et al., Environ Res., 2.23, 239(1): 117308). It even has carcinogenic effects (McDonald, Chemosphere, 2002, 46(5):745-755). Research on PBDE analysis and testing in my country started relatively late, but with technological development and the improvement of people's living standards, the production volume of related industrial products has increased year by year, and the detection rate and concentration of PBDEs worldwide have also increased year by year. As environmental pollution and food safety issues receive increasing attention, accurate and precise monitoring technologies and methods are crucial for the analysis, research, and early warning of PBDEs in the environment. Reliable and stable sampling and measurement technologies not only help assess the environmental risks and biotoxicity of PBDEs, but are also essential for understanding their environmental behavior.

[0003] Currently, the analysis of PBDEs concentrations in aquatic environments mainly employs active sampling, which involves collecting water samples on-site and bringing them back to the laboratory for analysis. The basic steps are as follows: the samples brought back to the laboratory are extracted according to their properties. Extraction methods include liquid-liquid extraction, Soxhlet extraction, ultrasonic extraction, cold column extraction, matrix solid-phase extraction, solid-phase extraction, accelerated solvent extraction, supercritical fluid extraction, microwave-assisted extraction, and solid-phase microextraction. The obtained extract is further concentrated and diluted to a fixed volume, and then analyzed using gas chromatography-mass spectrometry (GC-MS). These processes often result in low recovery rates and are not only cumbersome but also prone to introducing errors.

[0004] Passive sampling technology is a "green sampling technique" that allows analytes to diffuse freely from one medium (environment) into another medium (passive sampler). Because it requires no additional energy for sample collection, yet simultaneously provides pre-concentration, it significantly reduces sample pretreatment time and workload. Furthermore, passive sampling technology can determine the time-averaged concentration of pollutants, better capturing concentration fluctuations, and is simple to operate, time-saving, labor-saving, economical, and introduces minimal error. Diffusion gradients in thin films (DGT) is a passive sampling technique based on Fick's first law of diffusion, invented in the 1990s by David Williams and Hao Zhang of Lancaster University, UK. Since its invention, it has been widely used to determine bioavailable metal ions and some organic pollutants in water, soil, and sediments. However, research on using diffusion gradients in thin films to determine PBDEs in water has not yet been reported.

[0005] DGT devices can be categorized into three types: those for water, soil, and sediment. Regardless of the type, their basic structure consists of a filter membrane, a diffusion membrane, and an adsorption membrane, along with a shell that holds these three membranes in place. The filter membrane primarily prevents particulate matter in the test environment from damaging the diffusion and adsorption membranes; the diffusion membrane allows ions in solution to diffuse freely to the adsorption membrane; and the adsorption membrane is typically made of different adsorbent materials depending on the target analyte being measured. Therefore, a key parameter for evaluating the effectiveness of DGT technology is its ability to accurately quantify the concentration or effective form of the target analyte in the environment. Many factors influence the effectiveness of DGT in measuring target analytes, including whether the filter membrane and diffusion membrane over-adsorb the target analyte, the adsorption effect of the adsorption membrane, the pore size of the diffusion membrane, and the dynamic exchange process of different forms of the target analyte within the diffusion membrane. These parameters can be accurately measured in the laboratory, but deviations in target concentration measurement still exist in practical applications. Summary of the Invention

[0006] 1. The problem to be solved

[0007] To address the problems of low recovery rate and large concentration error in the determination of PBDEs in water by existing sampling techniques, this invention provides a method for determining PBDEs.

[0008] 2. Technical Solution

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] A method for determining PBDEs utilizes DGT technology to measure PBDEs in the water body to be tested. A DGT device is used for sampling. After sampling, an eluent is used to elute the adsorption membrane to obtain an eluent, and then the concentration of PBDEs in the eluent is measured. The binding membrane of the DGT device is a modified multi-walled carbon nanotube adsorption membrane.

[0011] Preferably, the modified multi-walled carbon nanotube adsorption membrane uses an agarose membrane as a substrate, in which modified multi-walled carbon nanotube particles are distributed. The modified multi-walled carbon nanotube particles are modified by ultrasonic modification in an alkaline dopamine solution, and the particle size is 0.5-2 micrometers in length and about 50 nm in diameter.

[0012] Preferably, the DGT device further includes a DGT housing, a diffusion membrane, and a filter membrane; the housing is made of stainless steel and is fixed by a snap-fit ​​method; the diffusion membrane is an agar diffusion membrane; and the filter membrane is a Nuclepore track etching filter membrane.

[0013] Preferably, the specific steps for determining PBDEs in the water body using DGT technology are as follows:

[0014] (1) Assembly of DGT device: The adsorption membrane, diffusion membrane and filter membrane are stacked on the base of DGT device from bottom to top, and the top cover with window is fastened on the base to assemble DGT device.

[0015] (2) Placement of DGT device: Place the DGT device from step (1) into the environmental medium to be tested (water, soil or sediment) for adsorption of PBDEs;

[0016] (3) Recovery and elution of adsorption membrane: After removing the DGT device from the test environment medium, rinse the device with pure water, remove the adsorption membrane and place it in a glass bottle, add eluent to obtain the eluent;

[0017] (4) Determination of PBDEs: The concentration of PBDEs in the eluent obtained in step (3) was determined by gas chromatography-secondary mass spectrometry.

[0018] Preferably, the specific preparation steps of the adsorption membrane are as follows:

[0019] (1) Surface modification of multi-walled carbon nanotubes was carried out using dopamine and then dried for later use;

[0020] (2) Mix agar powder, modified multi-walled carbon nanotubes and pure water in a certain mass ratio, shake well and heat to boiling to make it into a uniform black agar solution of modified multi-walled carbon nanotubes.

[0021] (3) The agar solution of the prepared modified multi-walled carbon nanotubes is injected into the gap between two glass plates with U-shaped Teflon sheets, the air bubbles between the glass plates are squeezed out, the glass plates are placed horizontally and cooled at room temperature for 50-80 minutes, and the solution in the glass plates solidifies to form an adsorption film.

[0022] Preferably, in step (1), the specific steps for surface modification of multi-walled carbon nanotubes using dopamine are as follows:

[0023] Dopamine solution: A 10 mmol / L dopamine solution, with pH adjusted to 9 (±0.5) using NaOH;

[0024] Carbon nanotube modification: Multi-walled carbon nanotubes were added to a dopamine solution to make the volume-to-mass ratio of dopamine solution to multi-walled carbon nanotubes 2:1 mL / g, sonicated for 30 min, and then dried.

[0025] Ultrapure water washing: Add pure water to the prepared material and shake it, centrifuge, remove the supernatant, repeat three times, and then dry.

[0026] Preferably, in step (2), the mass ratio of agar powder, modified multi-walled carbon nanotubes and pure water is 1:(5-10):50.

[0027] Preferably, the eluent is a mixture of methanol and dichloromethane, both of which are chromatographic grade, and the volume ratio of the mixture is 1:1.

[0028] Preferably, the PBDEs include one or more of tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, octabromodiphenyl ether, and decabromodiphenyl ether.

[0029] Preferably, the concentration of PBDEs in the water to be tested is between 0.006 and 500 mg / L.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) This invention provides a method for measuring PBDEs in the environment based on gradient diffusion film (DGT) technology, using an adsorption membrane prepared by modified multi-walled carbon nanotubes as the binding membrane, which can effectively realize the measurement of PBDEs in the environment.

[0033] (2) This invention provides a method for determining PBDEs in the environment. The method uses a DGT device for sampling. A modified multi-walled carbon nanotube adsorption membrane with high adsorption capacity and high recovery rate is selected and assembled with a stainless steel shell, an agar diffusion membrane and a Nuclepore track etching filter membrane to form a DGT device. This reduces the adsorption of target substances by the stainless steel shell and filter membrane, thereby eliminating the PBDEs measurement error caused by the adsorption of the shell and filter membrane, and realizing the in-situ determination of PBDEs in the environment by DGT technology.

[0034] (3) The method for determining PBDEs in the environment provided by this invention uses modified multi-walled carbon nanotubes (MWCNTs) with a particle size of 0.5-2 micrometers and a diameter of 50 nm as adsorbents to form a modified MWCNT adsorption membrane with agarose gel. The raw materials are inexpensive and readily available, and the preparation process is simple and time-saving. The modified MWCNTs are distributed in the agarose membrane matrix, and their small particle size allows for uniform distribution within the membrane matrix. Compared to HLB resin adsorption membranes, modified MWCNT adsorption membranes have a larger adsorption capacity and a higher recovery rate. This is because the modified MWCNTs can provide more adsorption sites for PBDEs. According to the inventors' tests, the adsorption capacity of the membrane prepared using modified MWCNTs is 2.5 times greater than that of the membrane prepared using HLB resin, and its recovery rate is increased by 10%. Attached Figure Description

[0035] Figure 1 A schematic diagram of the structure of a DGT device assembled with the modified carbon nanotube adsorption membrane prepared in Example 1 of the present invention;

[0036] Figure 2 This is a schematic diagram of the apparatus structure for measuring PBDEs in sediments using the DGT apparatus in Embodiment 3 of the present invention;

[0037] Figure 3 The adsorption effect of the DGT device in Example 4 of this invention on PBDEs at different pH values ​​is shown in the figure.

[0038] Figure 4 The adsorption effect of the DGT device in Example 5 of this invention on PBDEs at different ion concentrations is shown in the figure.

[0039] Figure 5 The image shows the adsorption effect of DGT devices with different filter membranes and shells on PBDEs in Comparative Example 2. Detailed Implementation

[0040] This disclosure will be more readily understood by referring to the following description, taken in conjunction with the accompanying drawings and examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0041] It should also be understood that, for clarity, certain features of this disclosure may be described herein in the context of individual embodiments, but may also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for brevity, various features of this disclosure described in the context of individual embodiments may also be provided individually or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure may also be considered an independent embodiment in itself.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0043] The present invention will be further illustrated below with reference to specific embodiments, but these embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. The essential features and significant effects of the present invention can be seen from the following embodiments. The described embodiments are some, but not all, embodiments of the present invention, and therefore do not limit the present invention in any way. Any non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are within the protection scope of the present invention.

[0044] The DGT device used in the following specific embodiments is as follows:

[0045] like Figure 1 As shown, the DGT device consists of a base 1, a fixing layer, a diffusion layer, a cover 5, and a buckle 6.

[0046] The fixing layer is an adsorption membrane 2 containing modified carbon nanotubes;

[0047] The diffusion layer includes a diffusion membrane 3 and a filter membrane 4; wherein, the diffusion membrane 3 is an agar diffusion membrane; and the filter membrane 4 is a Nuclepore track etching filter membrane.

[0048] The base 1 and the cover 5 are made of stainless steel.

[0049] The adsorption membrane containing modified carbon nanotubes used was prepared through the following steps:

[0050] (1) Prepare an alkaline solution of dopamine by dissolving dopamine in ultrapure water to a concentration of 10 mmol / L, and adjust the pH of the prepared solution to 9 (±0.5) with NaOH.

[0051] (2) Immerse the multi-walled carbon nanotubes in the solution prepared in (1) and treat them under ultrasonic conditions for 30 minutes. After treatment, centrifuge, discard the supernatant, spread them evenly in a petri dish, and dry them for later use. The diameter of the carbon nanotubes is 10-30 nm and the length is 1-2 μm.

[0052] (3) Mix agar powder, modified carbon nanotubes and pure water in a mass ratio of 1:5:50, shake well and heat the solution to boiling to obtain agar solution of modified carbon nanotubes.

[0053] (4) The prepared modified carbon nanotube agar solution is injected into the gap between two glass plates with U-shaped Teflon sheets, the air bubbles between the glass plates are squeezed out, the glass plates are placed horizontally and cooled at room temperature for 80 minutes, and the solution in the glass plates solidifies to form a modified carbon nanotube adsorption film.

[0054] The final product is an adsorption membrane with agarose membrane as the substrate and modified carbon nanotubes distributed on the surface of the agarose membrane.

[0055] Example 1

[0056] In this embodiment, the modified multi-walled carbon nanotube adsorption membrane described above is used as the binding membrane in DGT technology. The DGT technology is used to determine the PBDEs present in the water body to be tested. The specific detection steps are as follows:

[0057] (1) Assembly of the DGT device: The modified multi-walled carbon nanotube adsorption membrane, diffusion membrane, and filter membrane are sequentially stacked between the DGT base and the cover with a window to assemble the DGT device (e.g., Figure 1 As shown), the base and cover of the DGT device are made of stainless steel;

[0058] (2) Placement of DGT device: Place the DGT device from step (1) into water containing the PBDEs to be tested that has been thoroughly stirred, and leave it for a certain period of time.

[0059] (3) Recovery and elution of modified carbon nanotube adsorption membrane: After the DGT device is removed from the water body to be tested, the surface of the device is rinsed with pure water. Then the modified multi-walled carbon nanotube adsorption membrane is taken out, placed in a glass bottle, and eluent (1:1 solution of methanol and dichloromethane) is added. After ultrasonic treatment, the eluent is obtained and then filtered, concentrated and adjusted to a fixed volume.

[0060] (4) Determination of PBDEs: The concentration of PBDEs in the eluent obtained in step (3) was determined by gas chromatography-secondary mass spectrometry.

[0061] (5) Calculation of PBDEs adsorption capacity: The adsorption capacity of PBDEs on the modified carbon nanotube adsorption membrane is calculated according to the following formula (I).

[0062] M = C e (V g +V e ) / f e (I)

[0063] In the formula, M is the amount of PBDEs adsorbed on the adsorption membrane, in ng; C e V represents the molar concentration of PBDEs in the eluent, expressed in ng / mL. g V is the volume of the adsorption membrane, in mL; e This is the volume of the eluent, in mL; f e It is the elution efficiency of PBDEs, which is obtained by eluting an adsorption membrane with a known amount of PBDEs adsorbed.

[0064] According to Fick's first diffusion law, the concentration of DGT can be converted using the following formula (II), and the concentration of PBDEs in water can be calculated.

[0065] C DGT =M*Δ g / (D*A*t)(II)

[0066] In the formula, C DGT This refers to the concentration of PBDEs in water, expressed in ng / mL; Δ g It is the sum of the thicknesses of the diffusion membrane and the filter membrane, in cm; D is the diffusion coefficient of PBDEs in the diffusion membrane, in cm. 2 / s; A is the window area of ​​the DGT device, in cm². 2 t is the placement time of the DGT device, in seconds.

[0067] Example 2

[0068] In this embodiment, the modified carbon nanotube adsorption membrane described above is used as a binding membrane in DGT technology. The DGT technology is used to determine the PBDEs present in the soil to be tested. The specific detection steps are as follows:

[0069] (1) Assembly of the DGT device: The adsorption membrane 2 containing carbon nanotubes, the diffusion membrane 3, and the filter membrane 4 are sequentially stacked between the DGT base and the cover with the window, and assembled as follows. Figure 1 The DGT device shown is made of stainless steel, including the base and cover.

[0070] (2) Placement of the DGT device: Adjust the soil to be tested to a moisture content of 100% using pure water. Place the soil slurry in a glass petri dish. Carefully coat a small amount of soil slurry onto the window of the DGT device from step (1), and screw the device window downwards into the soil slurry in the petri dish to ensure full contact.

[0071] (3) Recovery and elution of adsorption membrane 2: After the DGT device is removed from the water body to be tested, the surface of the device is rinsed with pure water to remove dirt. Then the modified carbon nanotube adsorption membrane is removed, placed in a glass bottle, and eluent (a mixture of methanol and ammonia water in a 1:1 ratio) is added. After ultrasonic treatment, the eluent is obtained.

[0072] (4) Determination of PBDEs: The concentration of PBDEs in the eluent obtained in step (3) was determined by gas chromatography-secondary mass spectrometry.

[0073] (5) Calculation of PBDEs adsorption capacity: The adsorption capacity of PBDEs on adsorption membrane 2 is calculated according to the following formula (I).

[0074] M = C e (V g +V e ) / f e (I)

[0075] In the formula, M is the amount of PBDEs adsorbed on adsorption membrane 2, in ng; C e V represents the molar concentration of PBDEs in the eluent, expressed in ng / mL. g V is the volume of the adsorption membrane, in mL; e This is the volume of the eluent, in mL; f e It is the elution efficiency of PBDEs, which is obtained by eluting an adsorption membrane with a known amount of PBDEs adsorbed.

[0076] According to Fick's first diffusion law, the concentration of DGT can be converted using the following formula (II), and the concentration of PBDEs in water can be calculated.

[0077] C DGT =M*Δ g / (D*A*t)(II)

[0078] In the formula, C DGTThis refers to the concentration of PBDEs in water, expressed in ng / mL; Δ g It is the sum of the thicknesses of the diffusion membrane and the filter membrane, in cm; D is the diffusion coefficient of PBDEs in the diffusion membrane, in cm. 2 / s; A is the window area of ​​the DGT device, in cm². 2 t is the placement time of the DGT device, in seconds.

[0079] (6) Determination of PBDEs in soil: Soil slurry was collected from petri dishes, dried, and extracted with a mixture of methanol and ammonia to detect PBDEs.

[0080] (7) Compare the concentrations of PBDEs measured by DGT with the concentrations of PBDEs in the soil and obtain a stable ratio.

[0081] Example 3

[0082] In this embodiment, the modified carbon nanotube adsorption membrane described above is used as a binding membrane in DGT technology. The DGT technology is used to determine the PBDEs present in the sediment to be tested. The specific detection steps are as follows:

[0083] (1) Assembly of the DGT device: The adsorption membrane 2 containing carbon nanotubes, the diffusion membrane 3, and the filter membrane 4 are sequentially stacked between the DGT base and the cover with the window, and assembled as follows. Figure 2 The DGT device shown is made of stainless steel, including the base and cover.

[0084] (2) Placement of the DGT device: Place the sediment to be tested in a glass beaker. Carefully insert the DGT device from step (1) into the sediment, ensuring full contact.

[0085] (3) Recovery and elution of adsorption membrane 2: After the DGT device is removed from the water body to be tested, the surface of the device is rinsed with pure water to remove dirt. Then the modified carbon nanotube adsorption membrane is taken out, the adsorption membrane is divided according to the depth of the sediment and placed in glass bottles respectively. Eluent (a mixture of methanol and ammonia water in a 1:1 ratio) is added and then ultrasonically treated to obtain the eluent.

[0086] (4) Determination of PBDEs: The concentration of PBDEs in the eluent obtained in step (3) was determined by gas chromatography-secondary mass spectrometry.

[0087] (5) Calculation of PBDEs adsorption capacity: The adsorption capacity of PBDEs on adsorption membrane 2 is calculated according to the following formula (I).

[0088] M = C e (V g +V e ) / f e (I)

[0089] In the formula, M is the amount of PBDEs adsorbed on adsorption membrane 2, in ng; C e V represents the molar concentration of PBDEs in the eluent, expressed in ng / mL. g V is the volume of the adsorption membrane, in mL; e This is the volume of the eluent, in mL; f e It is the elution efficiency of PBDEs, which is obtained by eluting an adsorption membrane with a known amount of PBDEs adsorbed.

[0090] According to Fick's first diffusion law, the concentration of DGT can be converted using the following formula (II), and the concentration of PBDEs in water can be calculated.

[0091] C DGT =M*Δ g / (D*A*t)(II)

[0092] In the formula, C DGT This refers to the concentration of PBDEs in water, expressed in ng / mL; Δ g It is the sum of the thicknesses of the diffusion membrane and the filter membrane, in cm; D is the diffusion coefficient of PBDEs in the diffusion membrane, in cm. 2 / s; A is the window area of ​​the DGT device, in cm². 2 t is the placement time of the DGT device, in seconds.

[0093] (6) Determination of PBDEs in sediments: The sediment slurry in the petri dish was collected, dried, and extracted with a mixture of methanol and ammonia to detect the PBDEs.

[0094] (7) Compare the concentrations of PBDEs measured by DGT with the concentrations of PBDEs in the soil and obtain a stable ratio.

[0095] Example 4

[0096] This embodiment investigates the effect of DGT technology on the concentration of PBDEs in water at different pH levels. The concentration of PBDEs in the water to be tested is 20 μg / L, and the pH values ​​of the test solutions are 3.05, 5.01, 7.05, 8.03, and 9.51.

[0097] like Figure 3 As shown, the PBDEs concentration C calculated according to the formula DGT The concentration of PBDEs in the actual measured solution C solu The ratio was between 0.9 and 1.1, indicating that the pH of the water body had no significant effect on the determination of DGT.

[0098] Example 5

[0099] This embodiment is basically the same as embodiment 4, except that: in this embodiment, the effect of DGT technology on the determination of PBDEs in water under different ion concentrations is detected. In step (2) of determining PBDEs in water using a DGT device, the DGT device is placed in water containing the PBDEs to be tested that has been thoroughly stirred and left for 24 hours. The concentration of PBDEs in the water to be tested is 20 μg / L, and the ion concentrations (calculated as NaCl) of the water to be tested are 0.1, 1, 10, 100, and 500 mmol / L, respectively.

[0100] like Figure 4 As shown, the PBDEs concentration C calculated according to the formula DGT The concentration of PBDEs in the actual measured solution C solu The ratio is between 0.9 and 1.1, indicating that the ionic strength of the water body has no significant effect on the determination of DGT.

[0101] Comparative Example 1

[0102] This comparative example is basically the same as Example 1, except that there are two types of adsorption membranes in this comparative example: one is based on an agarose membrane with modified carbon nanotubes distributed in the agarose membrane; the other is based on an agarose membrane with activated HLB resin distributed in the agarose membrane.

[0103] The preparation process of the comparative adsorption membrane is basically the same as that in Example 1, with the only difference being:

[0104] In step (1), methanol is used to activate the HLB resin;

[0105] In step (2), agar powder, activated HLB resin and pure water are mixed in a certain mass ratio, shaken and heated to boiling to make it transparent to obtain an agar solution of HLB resin.

[0106] In step (3), the agar solution of the prepared HLB resin is injected into the gap between two glass plates sandwiched with U-shaped Teflon sheets, the air bubbles between the glass plates are squeezed out, the glass plates are placed horizontally and cooled at room temperature, and the solution in the glass plates solidifies to form an adsorption film.

[0107] Adsorption tests were conducted on water containing PBDEs, and the results showed that the adsorption capacity of the adsorption membrane prepared by modified carbon nanotubes was 2.2 times greater than that of the adsorption membrane prepared by HLB resin.

[0108] Table 1. Adsorption capacity of two different adsorption membranes for PBDEs

[0109] Effective adsorption capacity (μg) 31.8 71.23

[0110] Comparative Example 2

[0111] First, it should be noted that the DGT housing and filter membrane are crucial components of the DGT device. When using DGT technology to determine PBDEs in environmental media, it is necessary to select not only a suitable adsorption membrane but also a suitable filter membrane. The adsorption capacity of the filter membrane for the target analyte must be minimized to avoid affecting the diffusion of the target analyte to the adsorption membrane. Different organic compounds have different adsorption capacities on different filter membranes. Therefore, before method development, it is essential to select a suitable filter membrane for the target substance to reduce its adsorption or retention of the target analyte, which could lead to measurement errors. For the DGT housing, most DGT devices use polypropylene polymer. This is because DGT is currently primarily used to determine substances with low lipid solubility, which are not easily adsorbed onto polypropylene polymer. However, PBDEs are highly lipid-soluble and easily adsorb onto polypropylene polymer. Therefore, this comparative example uses housings made of both polypropylene polymer and stainless steel to select the appropriate housing to reduce the adsorption or retention of the target analyte, thus minimizing measurement errors.

[0112] This comparative example selected four types of filter membranes to test the adsorption performance of PBDEs on the filter membranes. The specific steps are as follows:

[0113] (1) Four types of filter membranes were selected: GH-polypropylene fiber membrane (GHP), Nuclepore track etching membrane (Nuclepore), polyethersulfone membrane (PES) and polytetrafluoroethylene membrane (PTFE). The new membranes were soaked in ultrapure water containing 0.01M NaCl for one day.

[0114] (2) Place the four membranes into a 10 mL Erlenmeyer flask containing a mixture of 20 μg / L tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, octabromodiphenyl ether and decabromodiphenyl ether, and shake at 25 °C for 24 hours.

[0115] (3) Take a 200 μ / L water sample from the Erlenmeyer flask before and after placing the membrane, and measure the concentration of the target substance in the water sample.

[0116] (4) Calculate the percentage of the target substance adsorbed by the membrane using the following formula:

[0117] Adsorption% = (C a -C b ) / Ca×100%

[0118] Where C a C is the original concentration of the target substance in the conical flask. b It is the concentration of the target substance in the conical flask after the membrane is removed.

[0119] like Figure 5As shown, the inventors, through professional theoretical analysis and repeated experiments, concluded that only the Nuclepore membrane adsorbs the least amount of the target substance. Filter membranes made of polyethersulfone or polytetrafluoroethylene can adsorb a large amount of PBDEs, causing the substance to be unable to form a diffusion gradient in the filter membrane and diffusion membrane and thus be captured by the adsorption membrane. Therefore, when measuring PBDEs in water, the Nuclepore membrane was selected as the filter membrane of the DGT device.

[0120] This comparative example uses two types of DGT shells: polypropylene polymer and stainless steel. The adsorption performance of PBDEs on the shells was tested. The specific steps are as follows:

[0121] (1) Place the two shells into a 100 mL Erlenmeyer flask containing a mixture of 20 μg / L tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, octabromodiphenyl ether and decabromodiphenyl ether, and shake at 25 °C for 24 hours.

[0122] (2) Take a 200 μ / L water sample from the Erlenmeyer flask before and after placing the membrane, and measure the concentration of the target substance in the water sample.

[0123] (3) Calculate the percentage of the target substance adsorbed by the membrane using the following formula:

[0124] Adsorption% = (C a -C b ) / Ca×100%

[0125] Where C a C is the original concentration of the target substance in the conical flask. b It is the concentration of the target substance in the conical flask after the membrane is removed.

[0126] like Figure 5 As shown, the inventors, through professional theoretical analysis and repeated experiments, concluded that the stainless steel shell adsorbs the least amount of target substances, while the polypropylene polymer shell adsorbs a large amount of PBDEs, preventing the substance from forming a diffusion gradient in the filter membrane and diffusion membrane and thus being captured by the adsorption membrane. Therefore, when measuring PBDEs in water, the stainless steel shell was selected as the shell of the DGT device.

Claims

1. A method for determining polybrominated diphenyl ethers, characterized in that: The DGT technology was used to determine polybrominated diphenyl ethers in the environmental medium to be tested. The DGT device was used for sampling. After sampling, the adsorption membrane was eluted with an eluent to obtain the eluent. Then the concentration of polybrominated diphenyl ethers in the eluent was measured. The environmental medium includes water, soil or sediment, and the adsorption membrane of the DGT device is a modified multi-walled carbon nanotube adsorption membrane. The modified multi-walled carbon nanotube adsorption membrane uses an agarose membrane as a substrate, in which modified multi-walled carbon nanotubes are distributed. The modified multi-walled carbon nanotubes have a tube length of 0.5-2 micrometers and a tube diameter of 50 nm. The modified multi-walled carbon nanotubes are modified with dopamine. The DGT device also includes a DGT housing, a diffusion membrane, and a filter membrane; the DGT housing is made of stainless steel, the diffusion membrane is an agar diffusion membrane, and the filter membrane is a Nuclepore track etching filter membrane. The specific steps for determining polybrominated diphenyl ethers (PBDEs) in a test water body using DGT technology are as follows: (1) DGT material preparation: DGT diffusion film was prepared using agarose; modified multi-walled carbon nanotubes were prepared and then combined with agarose to prepare an adsorption film; (2) Assembly of DGT device: The adsorption membrane, diffusion membrane and filter membrane are stacked sequentially between the base of DGT device and the cover with window to assemble DGT device; (3) Placement of DGT device: Place the DGT device from step (2) into the water body to be tested for adsorption of polybrominated diphenyl ethers; (4) Recovery and elution of adsorption membrane: After removing the DGT device from the water body to be tested, rinse the device with pure water, remove the adsorption membrane and place it in a glass bottle, add eluent, sonicate and filter to obtain the eluent; (5) Determination of polybrominated diphenyl ethers: The concentration of polybrominated diphenyl ethers in the eluent obtained in step (4) was determined by gas chromatography-secondary mass spectrometry. The specific preparation steps of the adsorption membrane are as follows: (1) Surface modification of multi-walled carbon nanotubes was performed using dopamine, and the nanotubes were dried for later use; (2) Mix agar powder, modified multi-walled carbon nanotubes and pure water in a certain mass ratio, shake well and heat to boiling to make it into a uniform black suspension, i.e., the agar solution of modified multi-walled carbon nanotubes. (3) The agar solution of the prepared modified multi-walled carbon nanotubes is injected into the gap between two glass plates with U-shaped Teflon sheets, the air bubbles between the glass plates are squeezed out, the glass plates are placed horizontally and cooled at room temperature for 50 to 80 minutes, and the solution in the glass plates solidifies to form an adsorption film. The eluent is a mixture of methanol and dichloromethane, both of which are chromatographic grade, and the volume ratio of the mixture is 1:

1.

2. The method for determining polybrominated diphenyl ethers according to claim 1, characterized in that: The specific steps for surface modification of multi-walled carbon nanotubes using dopamine are as follows: Surface modification of multi-walled carbon nanotubes: Multi-walled carbon nanotubes were added to a dopamine solution with pH 9, soaked, ultrasonically dispersed, and dried to obtain a loose solid; the pH of the dopamine solution was adjusted using NaOH; the concentration of the dopamine solution was 10 mmol / L; the volume-mass ratio of the dopamine solution to the multi-walled carbon nanotubes was 2 mL : 1 g.

3. The method for determining polybrominated diphenyl ethers according to claim 1, characterized in that: In step (2), the mass ratio of agar powder, modified multi-walled carbon nanotubes and pure water is 1:(5~10):

50.

4. The method for determining polybrominated diphenyl ethers according to claim 1, characterized in that: The polybrominated diphenyl ethers include one or more of tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, octabromodiphenyl ether, and decabromodiphenyl ether.

5. The method for determining polybrominated diphenyl ethers according to claim 1, characterized in that: When the test environment medium is water, the concentration of polybrominated diphenyl ethers in the test environment medium is between 0.006 and 500 mg / L.

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