CN113426420A

CN113426420A - DGT adsorption film and preparation method and application thereof

Info

Publication number: CN113426420A
Application number: CN202110727242.0A
Authority: CN
Inventors: 罗军; 颜鹂颍; 李彦莹
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2021-06-29
Filing date: 2021-06-29
Publication date: 2021-09-24
Anticipated expiration: 2041-06-29
Also published as: CN113426420B

Abstract

The invention discloses a DGT adsorption film and a preparation method and application thereof, belonging to the field of material preparation and compound monitoring. The DGT adsorption membrane is prepared by gelling activated functionalized polystyrene/divinylbenzene (PEP-2, 40-60 mu m) resin particles and agarose membrane forming liquid. The prepared PEP-2 adsorption membrane, the agarose diffusion membrane and the Polytetrafluoroethylene (PTFE) filter membrane are sequentially superposed to assemble a DGT device, and the DGT device can be used for in-situ monitoring of 16 natural and synthetic glucocorticoid compounds in a water body. The adsorption film has the advantages of simple structure, reasonable design and easy manufacture.

Description

DGT adsorption film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of gradient diffusion films, and particularly relates to a DGT adsorption film and a preparation method and application thereof.

Background

Glucocorticoids are important steroid hormones and are commonly used in the treatment of a variety of human ailments including asthma, allergies, rhinitis, bowel problems and skin disorders, among others. It has been found that glucocorticoid is finally discharged with feces and urine after oral administration to humans, and that a large amount of glucocorticoid and its metabolites enter sewage treatment plants (WWTPs) after human excretion, and a part of them enter natural waters by discharging sewage treatment plant wastewater, and glucocorticoid drugs have been widely detected in various natural waters and sewage treatment plants at present (Ai jia., et al, environ. sci. technol.,2016,50, 2870-. It has been reported that some glucocorticoids exert adverse effects on aquatic organisms even at low concentrations, for example, leading to increased blood glucose concentrations, muscle contraction, altered gene expression in fish, and the like (Jian gong., et al, environ. polunt., 2019,251, 102-109). Thus, the presence of glucocorticoids can produce endocrine disruption and other toxic effects on aquatic organisms exposed to them for long periods of time, and accumulate in various classes of organisms through the food chain (Andrea specialtini, et al, j.chromanogr.a., 2018,1540, 38-46). A stable and reliable monitoring technology needs to be developed to analyze the behavior of the glucocorticoid compound in the water environment, which is helpful for further risk assessment.

At present, the method which is most widely applied to monitoring glucocorticoid in a water environment relies on an active sampling method, namely, a large amount of water samples are collected, and pre-enrichment of the water samples is completed through SPE small columns. Because the concentration of glucocorticoid in natural water environment is low, a large amount of water samples need to be collected, and the process is time-consuming and labor-consuming. And the transportation, storage and a series of pretreatment processes of the sample can influence the properties of the glucocorticoid compound to be detected, and influence the accuracy of the determination result. Most importantly, the concentration of the glucocorticoid compound measured by an active sampling mode is only the instantaneous concentration during sampling, and cannot reflect the change of the concentration of the glucocorticoid compound in a period of time, so that the representativeness of the measurement result is influenced. Compared with an active sampling method, the passive sampling technology has the advantages that the influence of the sample transportation and storage process on the concentration of the object to be detected is avoided, a large amount of water samples do not need to be collected, and time and labor are saved. The passive sampler can be placed in the environment for a short time or a long time to perform enrichment capture on trace substances. And the result finally obtained by the passive sampling technology reflects the Time weighted average concentration (TWA) of the object to be detected in the placing process of the sampler, and the monitoring result is representative.

The sampling techniques currently applied to a large extent include a polar organic matter integrated sampler (POCIS) and a chemical trap (chemcacher), but these passive samplers are greatly influenced by water flow conditions, and under the condition of slow water flow, a diffusion boundary layer affects measurement accuracy (zuo yitao, et al, anal. chem.,2018,90, 10016-. Thin film Diffusion Gradients (DGTs) are widely used in water, soil and sediments. However, the application of DGT devices to in situ monitoring of glucocorticoids in water bodies has not been previously investigated.

Disclosure of Invention

1. Problems to be solved

Based on the defects that the sampling of glucocorticoid compounds in water bodies by the existing active sampling technology is large in required sample amount, the monitoring process is easy to influence the accuracy of results and the like, the invention aims to research a DGT adsorption film suitable for carrying out glucocorticoid compounds in water bodies, and researches show that the DGT adsorption film prepared by utilizing functionalized polystyrene/divinylbenzene (PEP-2) resin particles has excellent adsorption effect and is more suitable for in-situ monitoring of the glucocorticoid compounds in water bodies;

meanwhile, aiming at the preparation of the DGT adsorption film of functionalized polystyrene/divinylbenzene (PEP-2) resin particles, the invention provides a corresponding preparation method for avoiding film cracking and improving the mechanical strength of a film finished product.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a DGT adsorption membrane is formed by gelling an aqueous film-forming solution of polystyrene/divinylbenzene resin particles and agar powder;

the adsorption film contains polystyrene/divinylbenzene resin particles, the polystyrene/divinylbenzene is functionalized, and pyrrolidine groups and carbamido groups are introduced to the polyethylene divinylbenzene; the maximum particle diameter of the resin particles is 40-60 mu m;

the film-forming solution is obtained according to the following modes:

contacting and mixing raw material agar powder, polystyrene/divinylbenzene resin particles and pure water, and then heating to boiling to ensure that the raw material agar powder, the polystyrene/divinylbenzene resin particles and the pure water are transparent to form agarose solution containing PEP-2 resin particles;

in the raw materials, the mass ratio of polystyrene/divinylbenzene resin particles is not more than 13%; meanwhile, the mass ratio of the polystyrene/divinylbenzene resin particles to the agar powder is not more than 7.5 and not less than 5.

It should be noted that, in the research process, it is indeed found that the membrane prepared by using PEP-2 resin particles to obtain DGT has a very ideal adsorption effect on glucocorticoid compounds in water, but the following problems are encountered successively:

firstly, according to the traditional preparation method (application publication No. CN 111659358A), the film is very easy to crack in the film forming process, and the final film forming rate is very low and is only 10-30% of the previous film forming rate;

secondly, even if the final film is obtained, the mechanical strength is very poor in the process of preparing a DGT device or monitoring in situ at the later stage, and the breakage rate is as high as 90%;

based on this, it was found through repeated studies that the root cause of the problem is that agarose gel is a network structure maintained by virtue of hydrogen bonds between sugar chains. The preparation principle of the adsorption membrane is that a reticular structure formed inside agarose in the solidification process is utilized to fix corresponding resin materials. PEP-2 resin has a rich surface structure compared with other resins, which requires more fixed sites inside agarose to bind the resin. At this time, a new requirement is provided for the addition of water, resin and agar powder in the early-stage proportioning process, because the interior of the agarose gel cannot provide enough binding sites for the resin under the traditional proportioning condition. Especially, in the later stage of cooling and gelling the PEP-2 adsorption film, if the amount of the PEP-2 resin in the earlier stage is too much relative to that of the agarose gel, the extra resin which is not combined by the agarose gel is adhered to the surface of the agarose gel, and when the glass plate is pried open in the corresponding film forming time, the phenomenon of dry cracking on the surface of the agarose gel due to too much material can be found, or when the glass plate is pried open, part of the agarose gel appears to be complete, but in fact, the mechanical strength of the agarose gel is greatly reduced, and the subsequent application is influenced.

The preparation method of the DGT adsorption film comprises the following steps:

(1) contacting and mixing raw material agar powder, pure water and activated PEP-2 resin particles, and then heating to boiling to ensure that the mixture is transparent to form an agarose solution containing the PEP-2 resin particles;

wherein in the raw materials, the mass ratio of the polystyrene/divinylbenzene resin particles is 12-13%;

the mass ratio of the agar powder is 1.72 plus or minus 0.02 percent;

(2) injecting agarose solution containing PEP-2 resin particles into a film forming device, removing air bubbles, and cooling at room temperature to form a film.

Further, in the step (1), the mass ratio of the agar powder, the polystyrene/divinylbenzene resin particles and the pure water is 1: (7-7.5): 50.

further, in the step (1), the contact mixing comprises ultrasonic treatment, and the temperature of the ultrasonic solution is controlled to be not higher than 10 ℃ during ultrasonic treatment;

wherein the specific ultrasonic conditions are as follows:

carrying out ice bath ultrasound;

ultrasonic treatment for 5-10 min;

the ultrasonic frequency is not lower than 80KHz, preferably 99 KHz;

in the step (2), the film forming time is 30-40min after the solution is cooled to room temperature.

It should be noted here that, in fact, this step is another key point for ensuring the mechanical strength of DGT adsorption, and after the adjustment based on the above-mentioned ratio, the success rate of film preparation has been greatly improved, but the mechanical strength is still not ideal, and especially the problem of breakage is easy to occur during the use process, and the research is continued to find the breakage or the phenomenon of concentrated resin content or resin agglomeration exists, and the reason is that the part where the resin is excessively aggregated belongs to the part where the internal solidification of the film is insufficient. In the preparation process, because the selected PEP-2 resin has small particle size and large specific surface area, and functional active groups such as carbamido are introduced into the surface, intermolecular hydrogen bonds are easier to form, the surface charge of the resin is richer, the agglomeration phenomenon is easy to occur, and finally the phenomenon that the resin is not uniformly dispersed in gel in the gel preparation process is caused,

before heating and boiling, the solution can be rapidly and uniformly dispersed in a short time by using low-temperature, high-frequency and short-time ultrasound, so that the purpose of dispersion is achieved; a more important objective is to use ultrasound at low temperature, high frequency, and short time to reduce the viscosity and surface tension of the resin system so that the resin can better maintain dispersion in the agarose solution. When the ultrasonic treatment with low temperature, high frequency and short time is used, the step of heating and boiling is carried out, so that the dispersion state can be maintained and even a better dispersion effect can be achieved;

therefore, the problems of easy film cracking in the preparation process of the DGT adsorption film and easy damage in the use process of the film can be effectively solved by improving the early dispersion uniformity of the PEP-2 resin in the glue preparation solution and changing the proportion and the film forming time of the traditional glue preparation solution. In the traditional preparation process of the DGT film, the measures adopted before heating are generally to repeatedly suck and back into glue solution by using a liquid-transfering gun so as to achieve the aim of uniformly mixing.

Further, in the step (1), the PEP-2 resin particles are activated by the following steps:

methanol activation: mixing PEP-2 resin with methanol, shaking, activating, and separating out deposited solid;

specifically, a methanol solvent is added into a certain amount of PEP-2 resin, the mixture is shaken up and down to be fully and uniformly mixed, and then the mixture is centrifuged to remove supernatant liquid to obtain deposited solid; the volume-mass ratio of the methanol solvent to the PEP-2 resin is 3:2 mL/g;

ultra-pure water cleaning: and cleaning the deposited solid by using pure water, and separating to obtain the activated PEP-2 resin particles.

Specifically, pure water was added to the obtained precipitated solid, followed by shaking up and down to mix it thoroughly, centrifugation, removal of the supernatant, and repetition of 3 times to obtain activated PEP-2 resin.

A method for detecting glucocorticoid compounds in a water body based on a DGT technology comprises the following steps:

monitoring and adsorbing glucocorticoid compounds in the water body by using a DGT device;

then eluting the glucocorticoid compound adsorbed by the DGT device;

finally, determining the concentration of the glucocorticoid compound in the obtained eluent by adopting a method of high performance liquid chromatography-secondary mass spectrometry;

the DGT device comprises a filter membrane, a diffusion membrane and a PEP-2 adsorption membrane which are sequentially arranged according to the flow direction of a water body from inlet to outlet.

Further, the diffusion membrane is an agar diffusion membrane, and the filter membrane is a polytetrafluoroethylene filter membrane.

Furthermore, the elution condition is that methanol is used as an eluent, ultrasound is carried out for 30 minutes, the method is convenient and fast, the elution efficiency is high and stable, and the elution efficiency of the elution condition on the glucocorticoid compounds on PEP-2 is over 90 percent.

Further, the glucocorticoid compound comprises a natural glucocorticoid compound and a synthetic glucocorticoid compound;

wherein the natural glucocorticoid compound comprises one or more of hydrocortisone, cortisone, deoxycorticosterone and corticosterone;

the artificially synthesized glucocorticoid compound comprises one or more of beclomethasone, dexamethasone, flumethasone, desoximetasone, dexamethasone acetate, clobetasol propionate, triamcinolone diacetate, methylprednisolone, prednisone, budesonide, triamcinolone acetonide and amcinolone acetonide.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention provides a DGT adsorption film, which contains PEP-2 resin, and activated PEP-2 resin particles are uniformly distributed in an agar film matrix; the PEP-2 resin material is functionalized polystyrene/divinylbenzene, urea functional groups bonded on the surface of the PEP-2 resin material enable the PEP-2 resin material to have rich charge structures, so that the PEP-2 resin material has better binding capacity and adsorption effect on high-polarity organic matters, and the DGT device assembled by adsorption membranes prepared from the PEP-2 resin particles can effectively realize various natural and synthetic glucocorticoid compounds.

Meanwhile, according to the preparation method of the DGT adsorption membrane provided by the invention, the use amounts of the resin, the agar powder and the ultrapure water are adjusted in the preparation process of the membrane, so that the problem that the membrane is easy to crack in a membrane forming stage in the preparation process is solved, and the mechanical strength of the finished membrane is ensured.

(2) The PEP-2 resin is easy to aggregate due to particle size and surface characteristics, ultrasonic treatment steps are added before heating a contact mixture of agar powder, pure water and activated PEP-2 resin particles to boiling treatment, and in the heating and boiling process, the boiling state can keep the resin particles in a glue solution in a uniformly dispersed state, so that the success rate and uniformity of an adsorption film are greatly improved. If the ultrasonic step is not added, the PEP-2 material in the glue forming liquid is aggregated, and the phenomenon of nonuniform overall heating is also likely to occur in the subsequent heating process, so that the subsequent film forming and the quality of the film are influenced.

The PEP-2 resin material used in the invention can cause the problems of film dry cracking or film mechanical strength reduction caused by too much uncombined material attached to the surface of the hydrogel under each film forming time (20-50min) test when added according to the mass ratio of the traditional glue solution, so that the adding amount of the resin in the glue solution is properly reduced when the glue solution is prepared. In addition, when an adsorption membrane is prepared by using the PEP-2 resin material, the membrane forming time is too long (50min), and the agarose absorbs water and swells, so that the membrane surface has less water and is cracked. Therefore, the problems of easy film cracking in the preparation process of the DGT adsorption film and easy damage in the use process of the film can be effectively solved by improving the early dispersion uniformity of the PEP-2 resin in the glue preparation solution and changing the proportion and the film forming time of the traditional glue preparation solution.

(3) The method for in-situ monitoring the glucocorticoid compounds in the water body based on the DGT technology selects a PEP-2 adsorption membrane, an agar diffusion membrane and a Polytetrafluoroethylene (PTFE) filter membrane to assemble a DGT device; the adsorption film prepared from the PEP-2 resin particles is used as a binding phase, has higher binding rate and adsorption capacity for glucocorticoid compounds, and the prepared PEP-2 resin is uniformly distributed on the whole 'surface' of the adsorption film, so that the comprehensive adsorption of the whole film can be realized within the first time; the Polytetrafluoroethylene (PTFE) filter membrane can effectively reduce the adsorption of glucocorticoid compounds, thereby ensuring that the glucocorticoid compounds in the water body can be effectively and accurately determined.

(4) According to the method for in-situ monitoring of the glucocorticoid compounds in the water body based on the DGT technology, when the DGT is measured and elution of the adsorption gel is completed, more than 90% of glucocorticoid can be eluted by the adsorption gel adsorbing the substance to be detected in 10mL of methanol solution through ultrasonic treatment for 30 minutes, the elution efficiency is high-efficiency and stable, the method is simple, and the consumed time is short.

Drawings

FIG. 1 is a schematic diagram of the DGT device fabricated in example 1 of the present invention;

FIG. 2 shows the change of the adsorption capacity of the DGT device to various glucocorticoid compounds with the standing time in example 2 of the present invention, wherein the solid line in the figure represents the theoretical line obtained according to the first Fick law;

FIG. 3 is a graph showing the adsorption effect of the DGT device on various glucocorticoid compounds under different ionic strengths in example 3 of the present invention;

FIG. 4 is a graph showing the adsorption effect of a DGT device on various glucocorticoid compounds under different soluble organic matters in example 5 of the present invention;

FIG. 5 is a graph showing the adsorption effect of a DGT device with different filter membranes on various glucocorticoid compounds in comparative example 1;

FIG. 6 is a graph showing the adsorption effect of the DGT device using different types of adsorption membranes on different types of glucocorticoid compounds in comparative example 2.

In the figure: 1. a cover (made of ABS) with a window; 2. filtering the membrane; 3. a diffusion membrane; 4. an adsorption film; 5. DGT base (ABS material).

Detailed Description

The film forming device is characterized in that bubbles between two glass plates are discharged from a gap between the two glass plates with a U-shaped Teflon gasket of 0.5mm, and the glass plates are horizontally placed at room temperature and cooled for 30-40 minutes, so that solution in the glass plates is gelled to form a film.

As shown in FIG. 1, the DGT device used in the present invention comprises a cover 1 with a window, a filter membrane 2, a diffusion membrane 3, an adsorption membrane 4, and a DGT base (ABS material) 5 in sequence from the water inlet end to the water outlet end.

The DGT device is used for carrying out in-situ determination on the glucocorticoids in the water body by utilizing a DGT technology, and the specific determination steps are as follows:

(1) assembling of DGT device: sequentially superposing a PEP-2 adsorption membrane, an agarose diffusion membrane and a Polytetrafluoroethylene (PTFE) filter membrane on a DGT base, and covering and pressing a cover with a window to assemble the DGT device (as shown in figure 1), wherein the DGT base and the cover with the window are made of acrylonitrile-butadiene-styrene copolymer (ABS).

(2) Placement of DGT device: and (2) putting the assembled DGT device in the step (1) into an aqueous solution containing a glucocorticoid compound with a certain concentration, keeping the aqueous solution in a fully stirred state in the DGT placing process, and recording the temperature and time in the DGT placing process.

(3) Recovery and elution of the adsorption film in DGT: and (3) recovering the DGT placed in the step (2), flushing the device with ultrapure water, prying the DGT device, taking out the PEP-2 adsorption membrane, placing the membrane in 10mL of eluent (pure methanol), and performing ultrasonic treatment for 30 minutes to obtain eluent.

(4) Determination of glucocorticoid compounds in the eluate: and (3) determining the concentration of the glucocorticoid compound by adopting high performance liquid chromatography-secondary mass spectrometry.

(5) Calculating the adsorption quantity of the glucocorticoid compounds on the PEP-2 adsorption film: the adsorption amount of the glucocorticoid compound on the PEP-2 adsorption membrane was calculated according to the following formula (1).

Wherein M refers to the mass of the glucocorticoid compound adsorbed on the adsorption membrane, and the unit is ng; ce refers to the concentration of glucocorticoid compounds in the eluent, and the unit is ng/mL; vg is the volume of the adsorption film, and the unit is mL; ve refers to the volume unit of the eluent is mL; fe refers to the elution efficiency of the glucocorticoid compound on the adsorption membrane.

(6) Calculating the DGT determination concentration: and (3) converting the adsorption quantity of the substance to be detected on the adsorption film obtained in the step (5) into the concentration measured by DGT by using a formula (2) according to Fick's first diffusion law.

In the formula, C_DGTIs the concentration of the glucocorticoid compound measured by a DGT device, and the unit is ng/mL; Δ g is the thickness of the diffusion layer (including the filter membrane and the diffusion membrane) in cm; d is the diffusion coefficient of the glucocorticoid compound in the diffusion membrane and is expressed in cm²S; a is the window area of the DGT device in cm²(ii) a t is the placement time of the DGT device in units of s.

The agarose diffusion membrane was prepared as follows: weighing 0.16g of agar powder, adding the agar powder into 8mL of ultrapure water, shaking the agar solution in a beaker, placing the beaker on an electric furnace, heating until the solution is clear and transparent, pumping the solution into two preheated (70 ℃) glass plates with 0.75mm U-shaped Teflon gaskets, placing the glass plates for 30-40 minutes at room temperature, prying the glass plates by a blade, cutting the agarose gel into round pieces with the diameter of 2.51cm, and placing the round pieces in 0.01mol/L NaCl solution at 4 ℃ for storage.

Example 1

The adsorption film in the DGT device in the embodiment is prepared by taking PEP-2 resin particles (40-60 mu m) as raw materials, and the preparation method comprises the following steps:

(1) activation of PEP-2 resin Material

Methanol activation: adding 30mL of methanol solvent into 20g of PEP-2 resin particles, shaking up and down to enable the methanol to be in full contact with the resin particles, then centrifuging at the rotating speed of 3500r/min for 10 minutes, removing supernatant, and repeating the step 2 times to obtain a deposited solid.

Ultra-pure water cleaning: adding a certain volume of ultrapure water into the obtained deposited solid, shaking up and down to enable the ultrapure water to fully contact the activated resin particles, then centrifuging at the rotating speed of 3500r/min for 10 minutes, removing supernatant, and repeating the steps for 3 times to obtain the deposited solid.

(2) Preparation of PEP-2 adsorption membrane: agar powder, activated PEP-2 resin and ultrapure water were mixed in a ratio of 1: 7.5: 67, and carrying out ice bath ultrasonic treatment for 5min at the ultrasonic frequency of 99 KHz.

Heating the solution after ultrasonic treatment to boiling, pumping the solution into two preheated (70 ℃) glass plates with a 0.5mm U-shaped Teflon gasket, discharging bubbles between the glass plates, horizontally placing the glass plates at room temperature for cooling for 35 minutes until the solution between the glass plates is solidified into gel.

(3) Storage of PEP-2 adsorption film: after the solution is gelatinized, a glass plate is pried by a blade, the gelatinized PEP-2 adsorption film is cut into a wafer with the diameter of 2.51cm, and the wafer is stored in 0.01mol/L NaCl at the temperature of 4 ℃.

The PEP-2 adsorption membrane prepared in the embodiment can be used for measuring various natural and synthetic glucocorticoids, and is particularly suitable for in-situ monitoring of glucocorticoid compounds in water environment. The detection shows that the glucocorticoid compound in the water body to be detected can exist in one or more of the following simultaneously: beclomethasone (BCS), Dexamethasone (DEX), Flumethasone (FM), Desoximetasone (DES), dexamethasone acetate (21-DEXA), clobetasol propionate (CBSP), triamcinolone diacetate (TLD), Methylprednisolone (MPNL), Prednisone (PRE), Budesonide (BD), triamcinolone acetonide (TLA) and amcinolone Acetonide (AD).

The DGT device shown in FIG. 1 was assembled using the adsorption film in this example.

Example 2

In this example, the PEP-2 adsorption membrane, the agarose diffusion membrane and the Polytetrafluoroethylene (PTFE) filter membrane prepared in example 1 were assembled into a DGT device for measuring glucocorticoid compounds in water.

In this embodiment, the DGT device is used to monitor the glucocorticoid compounds in the water in situ, and the specific monitoring steps are as follows:

(1) placement of DGT device: and (2) placing the DGT device assembled in the step (1) in an aqueous solution containing a glucocorticoid compound with a certain concentration, keeping the aqueous solution in a fully stirred state in the DGT placing process, and recording the temperature of the aqueous solution in the DGT placing process and the DGT placing time.

(2) And (3) recovering and eluting the adsorption film: and taking out the placed DGT device, washing the surface with ultrapure water, prying the device with a crowbar, taking out the adsorption film in the device, and placing the adsorption film in eluent, wherein the eluent is 10mL of pure methanol solvent, and the elution condition is ultrasonic for 30 minutes.

(3) Determination of glucocorticoid compounds in the eluate: and (3) determining the concentration of the glucocorticoid compound by adopting high performance liquid chromatography-secondary mass spectrometry.

(4) Calculating the adsorption quantity of the glucocorticoid compounds on the PEP-2 adsorption film: the adsorption amount of the glucocorticoid compound on the PEP-2 adsorption membrane was calculated according to the following formula (1).

(5) Calculating the DGT determination concentration: and (3) converting the adsorption quantity of the substance to be detected on the adsorption film obtained in the step (5) into the concentration measured by DGT by using a formula (2) according to Fick's first diffusion law.

In this example, the diffusion coefficients of the glucocorticoid compounds are shown in Table 1.

TABLE 1 diffusion coefficients for various classes of glucocorticoid compounds

Compound (I)	D(10^-6cm²s^-1)
		CRL	4.81
COR	4.83
		DOC	4.27
C	4.69
		MPNL	4.75
PRE	4.85
		BCS	4.28
DEX	4.42
		FM	4.57
DES	3.80
		21-DEXA	4.03
AD	3.91
		CBSP	4.01
TLD	4.14
		BD	4.08
TLA	4.04

Window area a: 3.14cm²

The 16 glucocorticoid compounds were measured within 0 to 168 hours of measurement time.

Calculating the measured concentration (C) of each glucocorticoid compound according to the above formula_DGT) With an actual aqueous solution (C)_soln) The concentration ratio of the glucocorticoid compound (10 mu g/L) is within the range of 0.9-1.1, and the requirement of DGT determination is met.

Fig. 2 shows the change of the adsorption amount of various glucocorticoid compounds by using a DGT device along with the standing time, wherein the solid line in the figure is a theoretical line calculated according to the fick's first diffusion law, and the results show that the mass of the glucocorticoid compounds enriched on the PEP-2 adsorption film is highly consistent with the theoretical value, which indicates that the DGT can well determine the concentration of the glucocorticoid compounds in water under the condition of standing for a longer time.

Example 3

This embodiment is basically the same as embodiment 2 except that: in this embodiment, under the condition of monitoring different ionic strengths, the DGT technology is used to determine the influence of various glucocorticoid compounds in the water body, wherein the concentration of the glucocorticoid compound in the water body to be determined is 10 μ g/L, and the ionic strengths (in terms of NaCl) of the aqueous solution to be determined are respectively: 0.1, 10, 100 and 500 mmol/L.

FIG. 3 is a graph showing the adsorption effect of the DGT device on various glucocorticoid compounds under different ionic strengths in this example, and the results show that the glucocorticoid concentration C measured by DGT is calculated according to the formula_DGTWith the concentration of glucocorticosteroid in the aqueous solution (C)_soln) The ratio is in the range of 0.9-1.1, which indicates that the ionic strength of the water body has no obvious influence on the determination result of the DGT.

Example 4

This embodiment is basically the same as embodiment 2 except that: in step (2) of determining a glucocorticoid compound in a water environment by using a DGT device, the DGT device is placed in fully-stirred water containing the glucocorticoid compound for 24 hours, wherein the concentration of the glucocorticoid compound in the water to be measured is 10 μ g/L, and the concentrations of soluble organic matters (DOM) in the water solution to be measured are respectively as follows: 0. 4, 8, 12 and 20 mg/L.

FIG. 4 is a graph showing the adsorption effect of the DGT device on various glucocorticoid compounds under different soluble organic substances, and the results show the glucocorticoid concentration C measured by DGT calculated according to the formula_DGTWith the concentration of glucocorticosteroid in the aqueous solution (C)_soln) Range of ratioThe content of the soluble organic matter in the water is 0.9-1.1, which shows that the content of the soluble organic matter in the water has no obvious influence on the measurement result of the DGT.

Comparative example 1

The filter membrane is an important component of the DGT device, and if the filter membrane adsorbs a compound to be detected, the diffusion of a target substance to the adsorption membrane is influenced in the DGT measurement process, so that the accuracy of a DGT measurement result is influenced. Five common filter membranes are selected for the comparison example to carry out possible adsorption determination of the filter membranes on the glucocorticoid compounds, and the specific implementation steps are as follows:

(1) selecting five filter membranes, namely a GH-polypropylene fiber membrane (GHP), a mixed cellulose filter Membrane (MCE), a Nuclepor track etching membrane (Nuclepor), a polyether sulfone membrane (PES) and a polytetrafluoroethylene membrane (PTFE), and soaking the filter membranes in 0.01mol/L NaCl for at least 24 hours before the adsorption experiment is started.

(2) The four filters were placed in 10mL brown bottles containing 50. mu.g/L of a 16 glucocorticoid mixed solution and shaken at 25 ℃ for 24 hours at 200 r/min.

(3) And (4) taking water samples from the brown bottle before and after the start of the experiment to determine the concentration of the glucocorticoid compound in the water sample.

(4) The percentage of adsorption of the target substance by each type of filter membrane was calculated using the following formula.

Percent (%) adsorption (C)_b-C_a)/C_b×100％

Wherein, C_bRefers to the concentration of the target substance before the experiment, C_aRefers to the concentration of the target substance after the experiment.

Fig. 5 is a diagram of the adsorption effect of different filter membranes on various glucocorticoid compounds in the present comparative example, which shows that, according to the result, a polytetrafluoroethylene membrane (PTFE) produces the minimum adsorption (< 10%) on various glucocorticoid compounds, and a mixed fiber filter Membrane (MCE), polyether sulfone (PES), and GH-polypropylene fiber membrane (GHP) adsorb a large amount of glucocorticoid compounds, which may cause the formation of a diffusion gradient of a target substance in the filter membrane and the diffusion membrane, and the process of being captured by the adsorption membrane to be hindered when a DGT is subsequently assembled for placement, and thus, the measurement result is affected, and therefore, when the measurement of glucocorticoid compounds is performed in a water body, the polytetrafluoroethylene membrane (PTFE) is selected as the filter membrane in the DGT device.

Comparative example 2

When glucocorticoid compounds in a water body are monitored in situ by DGT, the adsorption film must have enough adsorption capacity to the compounds so as to ensure that the DGT device can still meet the monitoring requirement under the condition of long-time placement in high-concentration sewage. In the same manner as in example 4, the assembling process of the DGT device including the HLB and PEP-2 adsorption films in this comparative example was performed to compare and study the adsorption capacities of the two DGT devices to various glucocorticoid compounds, and the specific steps were as follows:

the HLB and PEP-2DGT devices prepared according to example 3 were immersed in 2.5L of well stirred water containing 0.01M NaCl and the glucocorticoid to be measured. Wherein the concentration of the glucocorticoid in the water body to be detected is 0, 200, 400, 600, 800 and 1000 mug/L. And (3) taking out the two DGT devices after being placed for 72h, eluting the adsorption film, measuring the concentration of a substance to be measured in the eluent, and determining the adsorption capacity of the HLB and PEP-2 adsorption films on the glucocorticoid compound.

As shown in fig. 6, the results demonstrate that the adsorption capacity of the adsorption film prepared using the PEP-2 resin is greater than that of the adsorption film prepared using HLB. Under the high-concentration placing condition, the concentration measured by the HLB adsorption film is lower than a theoretical value, and the concentration of the target substance measured by the PEP-2 adsorption film under each concentration accords with the theoretical value, so that the in-situ monitoring method is more suitable for long-time placing in high-concentration polluted water body for in-situ monitoring.

The analysis reason is mainly as follows: the inventor proves in experiments that when the concentration of the polar target compound in the HLB adsorption film is high, a competition effect is generated, so that the measurement value of the target compound by a DGT device containing the HLB adsorption film is reduced, and the measurement accuracy is influenced. For this reason, the HLB resin is a compound in which the polar group is retained by hydrophilic N-vinylpyrrolidone; the PEP-2 resin not only contains N-vinyl pyrrolidone groups, but also has carbamido functional groups bonded on the surface, and the carbamido functional groups enable the surface of the PEP-2 resin material to be rich in charges, so that the PEP-2 resin material has strong adsorption capacity on high-polarity compounds.

Comparative example 3

This comparative example is substantially the same as example 1 except that in step (2), prior to boiling by heating, no low-temperature, high-frequency, short-time sonication is carried out, but rather, the mixing is carried out by a conventional method, i.e., a pipetting gun is used to repeatedly suck and eject the deposition solution containing PEP-2 resin.

As a result, the PEP-2 adsorption membrane prepared by the method has various problems. Firstly, PEP-2 resin materials on an adsorption film prepared in a traditional mode are distributed very unevenly, materials in some areas are too concentrated, and resin agglomeration areas are easy to damage due to cracking or reduction of mechanical strength caused by the fact that the material quantity is large; while some regions have too little material and are insufficiently solidified at the corresponding film-forming time, or have an impaired adsorption performance due to an insufficient amount of material.

Comparative example 4

This comparative example is substantially the same as example 1 except that in step (2):

A. before heating and boiling, ultrasonic treatment is carried out at low temperature (ice bath) and low frequency (75KHz) instead of low temperature, high frequency and short time ultrasonic treatment; performing ultrasonic treatment for 5min and 20min to obtain final adsorption films A1 and A2;

B. before heating and boiling, ultrasonic treatment is carried out at a frequency of 99KHz in a non-ice bath manner without carrying out ultrasonic treatment at a low temperature and a high frequency for a short time; performing ultrasonic treatment for 5min and 20min to obtain final adsorption films B1 and B2;

for the a1, a2 samples:

although the samples A1 and A2 are successfully prepared, the breakage rate is still high in the using process, and breakage occurs before the adsorption is finished; the reason for this is that the PEP-2 resin has a tendency to disperse in the solution after the A1 sample is subjected to ultrasonication, but resin deposition is still observed at the bottom of the beaker, and the dispersion degree is not satisfactory; the A2 sample needs to be added with ice continuously in the ultrasonic process to achieve the purpose of temperature reduction, the steps are complicated, and if the temperature in the ultrasonic process is increased due to untimely addition of the ice, the PEP-2 resin in the solution tends to be reaggregated.

The samples B1 and B2 were broken at the initial stage of the use process, and the causes thereof were found to be: the damaged part or the phenomenon of concentrated resin content or resin agglomeration exists, and the reason is that the part where the resin is excessively aggregated belongs to the part where the solidification inside the membrane is insufficient; presumably due to the higher ultrasonic frequency, the temperature of both the B1 and B2 samples increased after the completion of the ultrasonic treatment; in two high-energy systems, PEP-2 resin is agglomerated to different degrees, and the ideal dispersion effect cannot be achieved.

Comparative example 5

c, sample: the film-forming solution is prepared according to the following mixture ratio:

the adding mass ratio of the agar powder to the polystyrene/divinylbenzene resin particles to the pure water is 1: 10: 50 and then heated to boiling to make it transparent, forming an agarose solution containing PEP-2 resin particles.

And D, sample: the film-forming solution is prepared according to the following mixture ratio:

the adding mass ratio of the agar powder to the polystyrene/divinylbenzene resin particles to the pure water is 1: 8: 50 and then heated to boiling to make it transparent, forming an agarose solution containing PEP-2 resin particles.

E, sample: the film-forming solution is prepared according to the following mixture ratio:

the adding mass ratio of the agar powder to the polystyrene/divinylbenzene resin particles to the pure water is 1: 7.5: 50 and then heated to boiling to make it transparent, forming an agarose solution containing PEP-2 resin particles.

For the C sample:

in the membrane preparation process, the C sample is cracked in the membrane forming process, and the membrane forming rate is only 10% -30% of that of the sample in the embodiment 1;

in the construction process of the DGT device, the mechanical strength of the adsorption film cut by using the sample C is poor, and about 90 percent of the adsorption film is damaged in the construction process;

in the DGT adsorption process, the performance of a DGT device built by using an adsorption film cut out from a C sample cannot meet the expected requirement (C)_DGT/C_soln<0.9)。

For the D sample:

in the membrane preparation process, the membrane forming rate of the D sample is increased (50-70%), but still needs to be further improved;

in the construction process of the DGT device, the mechanical strength of the D sample is moderate, and the breakage rate in the construction process of the DGT device is 50%;

in the DGT adsorption process, about 30-60% of the adsorption film cut out by the D sample is used for building a DGT device, and the expected requirements are not met (C)_DGT/C_soln<0.9)。

For sample E in example 1:

in the membrane preparation process, the E sample does not crack, and the membrane forming rate is high;

in the construction process of the DGT device, the mechanical strength of the E sample is good, and the cracking phenomenon does not occur;

in the DGT adsorption process, the R value (C) of the DGT device is built by using an adsorption film cut out from the E sample_DGT/C_soln) Are all within an acceptable range (0.9-1.1) and meet the adsorption requirement.

Claims

1. A DGT adsorption film is characterized in that: forming a film by gelling an aqueous film forming solution of polystyrene/divinylbenzene resin particles and agar powder;

the film-forming solution is obtained according to the following modes:

2. A method for preparing a DGT adsorption film according to claim 1, wherein: comprises the following preparation steps.

the mass ratio of the agar powder is 1.72 plus or minus 0.02 percent;

3. The method of producing a DGT-adsorbed film according to claim 2, wherein: in the step (1), the contact mixing comprises ultrasonic treatment;

wherein the specific ultrasonic conditions are as follows:

carrying out ice bath ultrasound;

ultrasonic treatment for 5-10 min;

the ultrasonic frequency is not lower than 80 KHz;

4. The method of producing a DGT adsorption film according to claim 3, wherein: in the step (1), the PEP-2 resin particles are activated by the following steps:

5. A method for detecting glucocorticoid compounds in a water body based on a DGT technology is characterized in that:

then eluting the glucocorticoid compound adsorbed by the DGT device;

the DGT device comprises a filter membrane, a diffusion membrane and an adsorption membrane containing PEP-2 resin particles which are sequentially arranged according to the flow direction of a water body from inlet to outlet.

6. The DGT technology-based method for detecting glucocorticoid compounds in water bodies according to claim 5, wherein: the diffusion membrane is an agar diffusion membrane, and the filter membrane is a polytetrafluoroethylene filter membrane.

7. The DGT technology-based method for detecting glucocorticoid compounds in water bodies according to claim 5, wherein: methanol was used as eluent.

8. The method for detecting glucocorticoid compounds in water body based on the DGT technology of any one of claims 5 to 7, wherein: the glucocorticoid compound comprises a natural glucocorticoid compound and an artificially synthesized glucocorticoid compound.

9. The DGT technology-based method for detecting glucocorticoid compounds in water bodies according to claim 8, wherein: the natural glucocorticoid compound comprises one or more of hydrocortisone, cortisone, deoxycorticosterone and corticosterone;