Determination method of polybrominated diphenyl ether substances

Abstract

The invention discloses a method for determining polybrominated diphenyl ether substances, which comprises the following steps: determining the polybrominated diphenyl ether substances in an environmental medium (water, soil and sediment) by using a DGT device, preparing a modified carbon nanotube adsorption film by using a modified multi-walled carbon nanotube with the particle size length of 0.5-2 microns and the diameter of about 50nm and an agarose film; the adsorption film is applied to a gradient diffusion film (DGT) technology, and a proper shell device, a diffusion film and a filter film are selected; after the adsorption is completed, a proper eluent is selected, so that the measurement error of the polybrominated diphenyl ether substances is eliminated to the greatest extent; the method is simple in preparation process, short in time consumption, simple and convenient in measurement and subsequent treatment procedures, and suitable for in-situ detection of the polybrominated diphenyl ether substances in the water body.

Description

Technical Field

[0001] The invention relates to the technical field of gradient diffusion films, and more specifically to a method for determining polybrominated diphenyl ether substances. Background Art

[0002] Polybrominated diphenyl ethers (PBDEs) are generally used as brominated flame retardants in textiles and plastic products. Because they can easily escape from products into the environment, the content of PBDEs in the environment has increased year by year in recent years. PBDEs have been widely detected in the atmosphere, water, soil, sediment, animals and plants, 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, the pollution level of PBDEs is even more serious. 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 enrich through the food chain and have bioaccumulation. There are many PBDEs homologues, but the most commonly used PBDEs in industry are mainly pentabromodiphenyl ether, octabromodiphenyl ether and decabromodiphenyl ether. Although the acute toxicity of PBDEs is low, studies have shown that its chronic toxicity can mainly act on organs such as the liver, kidney, and thyroid gland. In addition, a large number of experimental results have shown that PBDEs have endocrine disruption effects, reproductive toxicity, liver toxicity, neurotoxicity, immunotoxicity, developmental toxicity, etc. (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). my country started late in the research on PBDEs analysis and testing, but with the development of science and technology 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 are increasingly valued, accurate and precise monitoring technologies and methods are essential for the analysis, research and early warning of PBDEs in the environment. Reliable and stable sampling and measurement technologies are not only helpful in assessing the environmental risks and biological toxicity of PBDEs, but are also essential for understanding their environmental behavior.

[0003] At present, the analysis of PBDEs concentration in water environment mainly adopts active sampling method, that is, water samples are collected on site and brought back to the laboratory for determination. The basic steps are: the samples brought back to the laboratory are extracted according to their sample properties. The 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 fixed to volume, and then detected using gas chromatography-mass spectrometry. These processes often lead to lower recovery rates, and the process is not only very cumbersome but also easy to introduce errors.

[0004] Passive sampling technology is a "green sampling technology" that allows the analyte to enter another medium (passive sampler) through the free diffusion of molecules from one medium (environment). Because it does not require additional energy to complete sample collection, but at the same time can play a pre-enrichment role, greatly reducing the time consumption and workload of sample pretreatment. In addition, passive sampling technology can also measure the time-averaged concentration of pollutants, better capture the concentration fluctuations of pollutants, and is simple to operate, time-saving, labor-saving, economical, and introduces less error. Diffusive gradients in thin films (DGT) is a passive sampling technology based on Fick's first diffusion law invented by David Williams and Zhang Hao at Lancaster University in the United Kingdom in the 1990s. Since its invention, it has been widely used in the determination of effective metal ions and some organic pollutants in water, soil and sediment. However, there has been no report on the use of gradient diffusion thin film technology to determine PBDEs in water.

[0005] DGT devices can be divided into three types for use in water, soil and sediment. Regardless of the type, its basic structure is composed of a filter membrane, a diffusion membrane and an adsorption membrane, as well as a shell that fixes these three membranes. The filter membrane is mainly used to prevent particulate matter in the test environment from destroying the diffusion membrane and the adsorption membrane; the diffusion membrane allows ions in the solution to diffuse freely to the adsorption membrane; the adsorption membrane is generally made of different adsorption materials selected according to the target object to be measured. Therefore, a key parameter for measuring the effectiveness of DGT technology is its ability to accurately and quantitatively measure the concentration of the target in the environment or its effective state. There are many factors that affect the effect of DGT on the determination of the target, including: whether the outer shell filter membrane and diffusion membrane of DGT will over-adsorb the target, the adsorption effect of the adsorption membrane on the target, the pore size of the diffusion membrane, and the dynamic exchange process of various forms of the target in the diffusion membrane. These parameters can be accurately measured in the laboratory, but in actual applications, there are still deviations in the measurement of target concentration. Summary of the invention

[0006] 1. Problem to be solved

[0007] In view of the problems that the existing sampling technology has a low recovery rate and a large concentration error in the determination of PBDEs in water, the present invention provides a method for determining PBDEs.

[0008] 2. Technical solution

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

[0010] A method for determining PBDEs uses the DGT technology to determine PBDEs in a water body to be determined. A DGT device is used for sampling. After the sampling is completed, an eluent is used to elute the adsorption film to obtain an eluate, and then the concentration of PBDEs in the eluate is determined. 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 film is based on an agarose film, 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 have a particle size of 0.5-2 microns in length and about 50 nm in diameter.

[0012] Preferably, the DGT device further comprises a DGT housing, a diffusion membrane and a filter membrane; the housing is made of stainless steel and is fixed in a snap-on manner; the diffusion membrane is an agar diffusion membrane; and the filter membrane is a Nuclepore track-etched filter membrane.

[0013] Preferably, the specific steps of using DGT technology to determine PBDEs in the water to be tested are as follows:

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

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

[0016] (3) Recovery and elution of the adsorption film: After the DGT device is removed from the environmental medium to be tested, the device is rinsed with pure water, the adsorption film is removed and placed in a glass bottle, and the eluent is obtained after adding the eluent;

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

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

[0019] (1) Surface modification of multi-walled carbon nanotubes using dopamine and drying the surface of the multi-walled carbon nanotubes for later use;

[0020] (2) mixing agar powder, modified multi-walled carbon nanotubes and pure water in a certain mass ratio, shaking and heating to boiling to form a uniform black agar solution of modified multi-walled carbon nanotubes;

[0021] (3) The prepared modified multi-walled carbon nanotube agar solution is injected into the gap between two glass plates sandwiched by a U-shaped Teflon sheet, the 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.

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

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

[0024] Carbon nanotube modification: adding multi-walled carbon nanotubes to the dopamine solution so that the volume mass ratio of the dopamine solution to the multi-walled carbon nanotubes is 2:1 mL / g, ultrasonicating for 30 minutes, and then drying;

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

[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 mixed volume ratio 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, it is characterized in that 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 present invention has the following beneficial effects:

[0032] (1) The present invention provides a method for determining PBDEs in the environment based on gradient diffusion thin film (DGT) technology, using an adsorption film prepared from modified multi-walled carbon nanotubes as a binding membrane, which can effectively achieve the determination of PBDEs in the environment;

[0033] (2) The present invention provides a method for determining PBDEs in the environment, which adopts a DGT device for sampling, selects a modified multi-walled carbon nanotube adsorption membrane with high adsorption capacity and high recovery rate, and assembles it into a DGT device with a stainless steel shell, an agar diffusion membrane and a Nuclepore track-etched filter membrane, thereby reducing the adsorption of the target substance by the stainless steel shell and the filter membrane, thereby eliminating the PBDEs determination error caused by the adsorption of the shell and the filter membrane, and realizing the in-situ determination of PBDEs in the environment by the DGT technology;

[0034] (3) The method for determining PBDEs in the environment provided by the present invention uses modified multi-walled carbon nanotubes with a particle size of 0.5-2 microns and a diameter of 50 nm as an adsorbent and forms a modified multi-walled carbon nanotube adsorption film with agar gel. The raw materials are cheap and easy to obtain, and the preparation process is simple and time-consuming. The agarose film is used as a matrix, in which modified multi-walled carbon nanotubes are distributed. The particle size is small and can be evenly distributed in the film matrix. Compared with the HLB resin adsorption film, the modified multi-walled carbon nanotube adsorption film has a larger adsorption capacity and a higher recovery rate. The reason is that the modified multi-walled carbon nanotubes can provide more adsorption sites for PBDEs. According to the inventor's test, the adsorption capacity of the adsorption film prepared using modified multi-walled carbon nanotubes is 2.5 times greater than that of the adsorption film prepared using HLB resin, and its recovery rate is increased by 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The schematic diagram of the structure of the 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 structure of a device for measuring PBDEs in sediment using the DGT device in Example 3 of the present invention;

[0037] Figure 3 This is a diagram showing the adsorption effect of PBDEs at different pH values ​​using the DGT device in Example 4 of the present invention;

[0038] Figure 4 This is a diagram showing the adsorption effect of PBDEs at different ion concentrations using the DGT device in Example 5 of the present invention;

[0039] Figure 5 This is a diagram showing the adsorption effect of PBDEs by the DGT device using different filter membranes and different housings in Comparative Example 2; DETAILED DESCRIPTION

[0040] The present disclosure may be more easily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or shown herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise stated.

[0041] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure itself may also be considered to be an independent embodiment.

[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 the invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0043] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The essential characteristics and remarkable effects of the present invention can be reflected from the following examples, and the described embodiments are part of the embodiments of the present invention, rather than all the embodiments, and therefore, they do not limit the present invention in any way, and those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all belong to 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 fixed layer is an adsorption film 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-etched filter membrane;

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

[0049] The adsorption film containing modified carbon nanotubes is prepared by the following steps:

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

[0051] (2) Soaking the multi-walled carbon nanotubes in the solution prepared in (1) and treating them under ultrasonic conditions for 30 minutes, centrifuging them after treatment, discarding the supernatant, spreading them evenly in a culture dish and drying them for later use. The carbon nanotubes have a diameter of 10-30 nm and a length of 1-2 μm;

[0052] (3) mixing agar powder, modified carbon nanotubes and pure water in a mass ratio of 1:5:50, shaking well and heating the solution to boiling to obtain an agar solution of modified carbon nanotubes;

[0053] (4) The prepared modified carbon nanotube agar solution is injected into the gap between two glass plates sandwiched by a U-shaped Teflon sheet, the 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] Finally, an adsorption film is obtained, which takes agarose film as a matrix and has modified carbon nanotubes distributed on the surface of the agarose film.

[0055] Example 1

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

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

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

[0059] (3) Recovery and elution of modified carbon nanotube adsorption film: After taking the DGT device out of the water body to be tested, rinse the dirt on the surface of the device with pure water, then take out the modified multi-walled carbon nanotube adsorption film and place it in a glass bottle. After adding eluent (a 1:1 solution of methanol and dichloromethane) and ultrasonic treatment, the eluate is obtained, and the eluate is filtered, concentrated and fixed to volume.

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

[0061] (5) Calculation of PBDEs adsorption amount: The adsorption amount of PBDEs on the modified carbon nanotube adsorption film was calculated according to the following formula (I):

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

[0063] Where, M is the amount of PBDEs adsorbed on the adsorption film, in ng; C e is the substance concentration of PBDEs in the eluate, in ng / mL; V g is the volume of the adsorption film, in mL; V e is the volume of the eluent in mL; f e is the elution efficiency of PBDEs, which is obtained by eluting the adsorption membrane with a known amount of PBDEs adsorbed;

[0064] According to Fick's first diffusion law, the concentration of DGT is converted using the following formula (II) to calculate the concentration of PBDEs in water:

[0065] C DGT =M*Δ g / (D*A*t)(II)

[0066] In the formula, C DGT is the concentration of PBDEs in water, in ng / mL; Δ g is the sum of the thickness 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, unit: cm 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 is used as a binding membrane in the DGT technology, and the PBDEs present in the soil to be tested are determined by the DGT technology. The specific detection steps are as follows:

[0069] (1) Assembly of 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 a window to form a DGT device as shown in FIG. Figure 1 The DGT device shown, wherein the base and the cover of the DGT device are made of stainless steel;

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

[0071] (3) Recovery and elution of adsorption film 2: After the DGT device is taken out from the water body to be tested, the dirt on the surface of the device is rinsed with pure water, and then the modified carbon nanotube adsorption film is taken out and placed in a glass bottle. After adding an eluent (a mixture of methanol and ammonia water in a ratio of 1:1), ultrasonic treatment is performed to obtain the eluate.

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

[0073] (5) Calculation of PBDEs adsorption amount: The adsorption amount of PBDEs on the adsorption film 2 was calculated according to the following formula (I):

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

[0075] Where, M is the amount of PBDEs adsorbed on the adsorption membrane 2, in ng; C e is the substance concentration of PBDEs in the eluate, in ng / mL; V g is the volume of the adsorption film, in mL; V e is the volume of the eluent in mL; f e is the elution efficiency of PBDEs, which is obtained by eluting the adsorption membrane with a known amount of PBDEs adsorbed;

[0076] According to Fick's first diffusion law, the concentration of DGT is converted using the following formula (II) to calculate the concentration of PBDEs in water:

[0077] C DGT =M*Δ g / (D*A*t)(II)

[0078] In the formula, C DGTis the concentration of PBDEs in water, in ng / mL; Δ g is the sum of the thickness 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 cm 2 ; t is the placement time of the DGT device, in seconds.

[0079] (6) Determination of PBDEs in soil: The soil slurry in the culture dish was collected, dried, and the PBDEs therein were extracted using a mixture of methanol and ammonia water, and then tested on a machine.

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

[0081] Example 3

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

[0083] (1) Assembly of 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 a window to form a DGT device as shown in FIG. Figure 2 The DGT device shown, wherein the base and the cover of the DGT device are made of stainless steel;

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

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

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

[0087] (5) Calculation of PBDEs adsorption amount: The adsorption amount of PBDEs on the adsorption film 2 was calculated according to the following formula (I):

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

[0089] Where, M is the amount of PBDEs adsorbed on the adsorption membrane 2, in ng; C e is the substance concentration of PBDEs in the eluate, in ng / mL; V g is the volume of the adsorption film, in mL; V e is the volume of the eluent in mL; f e is the elution efficiency of PBDEs, which is obtained by eluting the adsorption membrane with a known amount of PBDEs adsorbed;

[0090] According to Fick's first diffusion law, the concentration of DGT is converted using the following formula (II) to calculate the concentration of PBDEs in water:

[0091] C DGT =M*Δ g / (D*A*t)(II)

[0092] In the formula, C DGT is the concentration of PBDEs in water, in ng / mL; Δ g is the sum of the thickness 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, unit: cm 2 ; t is the placement time of the DGT device, in seconds.

[0093] (6) Determination of PBDEs in sediments: The sediment slurry in the culture dish was collected, dried, and the PBDEs therein were extracted using a mixture of methanol and ammonia water, and then tested on an instrument.

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

[0095] Example 4

[0096] This example detects the effects of PBDEs in water using the DGT technology at different pH values, wherein the concentration of PBDEs in the water to be tested is 20 μg / L, and the pH values ​​of the aqueous solutions to be tested are 3.05, 5.01, 7.05, 8.03, and 9.51, respectively.

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

[0098] Example 5

[0099] This embodiment is basically the same as embodiment 4, except that: this embodiment detects the influence of different ion concentrations on the determination of PBDEs in water using DGT technology. In step (2) of using the DGT device to determine PBDEs in water, the DGT device is placed in fully stirred water containing the PBDEs to be tested for 24 hours, wherein the concentration of PBDEs in the water to be tested is 20 μg / L, and the ion concentration (in terms of NaCl) of the aqueous solution to be tested is 0.1, 1, 10, 100, and 500 mmol / L, respectively.

[0100] like Figure 4 As shown in the figure, the PBDEs concentration C calculated according to the formula DGT Compared with the actual PBDEs concentration in the measured solution, C solu The ratio is between 0.9 and 1.1, indicating that the ionic strength of water 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 described in this comparative example, one is based on agarose membrane, in which modified carbon nanotubes are distributed; the second is based on agarose membrane, in which activated HLB resin is distributed.

[0103] The preparation process of the adsorption film in this comparative example is basically the same as that in Example 1, except that:

[0104] In step (1), the HLB resin is activated by methanol;

[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 them transparent to obtain an agar solution of HLB resin;

[0106] In step (3), the prepared HLB resin agar solution is injected into the gap between two glass plates sandwiching a U-shaped Teflon sheet, the 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] The results of the test on water containing PBDEs showed that the adsorption capacity of the adsorption film prepared by modified carbon nanotubes was 2.2 times higher than that of the adsorption film prepared by HLB resin.

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

[0109] Adsorption film HLB Carbon Nanotubes Effective adsorption capacity (μg) 31.8 71.23

[0110] Comparative Example 2

[0111] First of all, it should be pointed out that the DGT shell and filter membrane are important components of the DGT device. When using the DGT technology to determine PBDEs in environmental media, it is necessary not only to select a suitable adsorption membrane, but also to select a suitable filter membrane. The adsorption amount of the filter membrane for the target must be as small as possible so as not to affect the diffusion of the target to the adsorption membrane. Different organic substances have different adsorption capacities on different filter membranes. Therefore, before the method is developed, a suitable filter membrane must be selected for the target substance to reduce its adsorption or retention of the detection target, causing measurement errors. For the DGT shell, most DGT devices are made of polypropylene polymer. This is because DGT is currently basically used to determine substances with low fat solubility and is not easily adsorbed on polypropylene polymers, but PBDEs are highly fat-soluble and easily adsorbed on polypropylene polymers. Therefore, this comparative example uses shells made of polypropylene polymers and stainless steel. A suitable shell is selected to reduce its adsorption or retention of the detection target, causing measurement errors.

[0112] This comparative example selected four 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, namely GH-polypropylene fiber membrane (GHP), Nuclepore track-etched membrane (Nuclepore), polyethersulfone membrane (PES) and polytetrafluoroethylene membrane (PTFE). The new membranes were soaked in ultrapure water containing 0.01 M NaCl for one day.

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

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

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

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

[0118] Among them C a is the original target concentration in the conical flask, C b is the concentration of the target substance in the conical flask after taking out the membrane.

[0119] like Figure 5As shown, the inventors have concluded through professional theoretical analysis and repeated experiments that only the Nuclepore membrane has the least adsorption of the target substance, and the filter membrane 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 the diffusion membrane and then be captured by the adsorption membrane. Therefore, when measuring PBDEs in water, the Nuclepore membrane is selected as the filter membrane of the DGT device.

[0120] This comparative example selects two DGT shells, polypropylene polymer and stainless steel, to test the adsorption performance of PBDEs on the shells. The specific steps are as follows:

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

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

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

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

[0125] Among them C a is the original target concentration in the conical flask, C b is the concentration of the target substance in the conical flask after the membrane is taken out.

[0126] like Figure 5 As shown, the inventors have concluded through professional theoretical analysis and repeated experiments that the stainless steel shell has the least adsorption of the target substance, and the polypropylene polymer shell adsorbs a large amount of PBDEs, causing the substance to be unable to form a diffusion gradient in the filter membrane and the diffusion membrane and then be captured by the adsorption membrane. Therefore, when measuring PBDEs in water, the stainless steel shell is selected as the shell of the DGT device.

Claims

1. A method for determining polybrominated diphenyl ethers, characterized in that: The DGT technique is used to determine the polybrominated diphenyl ether substances in the environmental medium to be tested. The DGT device is used for sampling. After the sampling is completed, the adsorption film is eluted with an eluent to obtain an eluent, and then the concentration of polybrominated diphenyl ether substances in the eluent is determined; The environmental medium includes water, soil or sediment, and the combined membrane of the DGT device is a modified multi-walled carbon nanotube adsorption membrane.

2. The method for determining polybrominated diphenyl ethers according to claim 1, wherein: The modified multi-walled carbon nanotube adsorption film is based on agarose film, in which modified multi-walled carbon nanotubes are distributed. The modified multi-walled carbon nanotubes have a particle length of 0.5-2 microns and a diameter of 50 nm. The modified multi-walled carbon nanotubes are modified with dopamine.

3. The method for determining polybrominated diphenyl ethers according to claim 2, characterized in that: The DGT device also includes a DGT shell, a diffusion membrane and a filter membrane; the DGT shell is made of stainless steel, the diffusion membrane is an agar diffusion membrane; and the filter membrane is a Nuclepore track-etched filter membrane.

4. The method for determining polybrominated diphenyl ethers according to any one of claims 1 to 3, characterized in that: The specific steps for using DGT technology to determine polybrominated diphenyl ethers in the water to be tested are as follows: (1) DGT material preparation: DGT diffusion membrane was prepared using agarose. Modified multi-walled carbon nanotubes were prepared and used together with agarose to prepare adsorption films. (2) Assembly of the DGT device: The adsorption membrane, diffusion membrane and filter membrane are sequentially stacked between the base of the DGT device and the lid with a window to assemble the DGT device; (3) Placement of the DGT device: Place the DGT device in step (2) into the water body to be tested to adsorb polybrominated diphenyl ethers; (4) Recovery and elution of adsorption film: After taking the DGT device out of the water body to be tested, rinse the device with pure water, take out the adsorption film and place it in a glass bottle, add the eluent, perform ultrasonic treatment and filter to obtain the eluate; (5) Determination of polybrominated diphenyl ethers: The concentration of polybrominated diphenyl ethers in the eluate obtained in step (4) was determined by gas chromatography-mass spectrometry.

5. The method for determining polybrominated diphenyl ethers according to claim 4, characterized in that: The specific preparation steps of the adsorption film are as follows: (1) using dopamine to modify the surface of multi-walled carbon nanotubes, and drying them for later use; (2) mixing agar powder, modified multi-walled carbon nanotubes and pure water in a certain mass ratio, shaking and heating to boiling to form a uniform black suspension, i.e., an agar solution of modified multi-walled carbon nanotubes; (3) The prepared modified multi-walled carbon nanotube agar solution is injected into the gap between two glass plates sandwiched by a U-shaped Teflon sheet, the 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.

6. The method for determining polybrominated diphenyl ethers according to claim 5, characterized in that: In the step (1), the specific steps of surface modification of multi-walled carbon nanotubes using dopamine are as follows: Surface modification of multi-walled carbon nanotubes: multi-walled carbon nanotubes are added to a dopamine solution with a pH of 9, immersed, ultrasonically dispersed, and dried to obtain loose solids; the pH of the dopamine solution is adjusted using NaOH; the concentration of the dopamine solution is 10 mmol / L; the volume mass ratio of the dopamine solution to the multi-walled carbon nanotubes is 2:1 mL / g.

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

50.

8. The method for determining polybrominated diphenyl ethers according to claim 5, characterized in that: The eluent is a mixture of methanol and dichloromethane, both of which are chromatographic grade, and the mixed volume ratio is 1:

1.

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

10. The method for determining polybrominated diphenyl ethers according to claim 9, characterized in that: The concentration of polybrominated diphenyl ether substances in the water to be tested is between 0.006 and 500 mg / L.

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