| Steroid hormones are a class of substances with structure of cyclopentane polyhydrogen phenanthrenes.They have a clear role in maintaining life,regulating sexual function,and in the development of the body,immune regulation,skin disease treatment and birth control.Their disorders caused by metabolic reasons or excessive intake could lead to various diseases.Meanwhile,steroid hormones are widely used in humans and animals due to their curative effect.Because they cannot be completely metabolized in the body,they are excreted into the environmental water by humans and animals,and become an environmental pollutant.They are not only harmful to the environment,but also can enter human body by food chain and thus affect human health.Therefore,it is necessary to determine the levels of steroid hormones in body fluids and environmental water samples.Low steroid hormone concentrations and complex environmental and biological matrices make pretreatment steps indispensable to achieve the purpose of enrichment and purification.Accordingly,the selection of new adsorbents with good enrichment effect on the target and the development of new type of sample pretreatment method that is environment-friendly,fast,and simple have become the focus,difficulty,and highlight of research in the field of environmental analytical chemistry.Metal-organic frameworks(MOFs)are a kind of recently identified porous nanometer materials.They have gained considerable attention in the field of sample pretreatment due to their ultrahigh porosity,tunable pore and crystal size and modifiable framework with chemical groups,enormous internal surface areas.This dissertation focuses on the utilization of MOFs as adsorbents for new sample pretreatment technologies in the analysis of water samples and urine samples.In addition,the further investigation of MOFs on the adsorption mechanism and adsorption property for estrogens is performed to provide theoretical support for the analysis and detection of steroid hormones in environmental water samples and urine samples.The main contents are summarized as follows:1.Four water-stable MOFs,MIL-53(Al),MIL-53(Fe),NH2-MIL-53(Al)and UiO-66(Zr)were synthesized by hydrothermal methods and the characterization was completed by means of SEM,XRD,and so on.In order to solve the problem of long reaction time of MIL-53(Al)by hydrothermal method,a microwave synthesis method was established.The synthesis conditions were optimized by the adsorption recoveries of three estrogens(E2,E3,and EE2),and the reaction time was successfully reduced from 3 days to 90 min.2.Computational and experimental methods were used to study the adsorption of 12 steroid hormones on four MOFs(MIL-101(Cr),MIL-100(Fe),MIL-53(Al),and UiO-66(Zr)).Based on the results of computer simulation and experiment,UiO-66(Zr)was used for the adsorption of androgens and progestogens,and MIL-53(Al)was used for the adsorption of glucocorticoids and estrogens.Besides,the binding modes and binding energies between the four MOFs and the targets were calculated,and the adsorption mechanism was elucidated at the atomic level.The interactions between them were mainly hydrophobic effects,hydrogen bonds and π-π interactions,and so on.Therefore,the combination of experimental and computational method can facilitate the development of MOFs and their efficient use in sample preparation.3.UiO-66(Zr)was applied as the sorbent in the porous membrane-protected micro-solid-phase extraction(μ-SPE)device for the pre-concentration of androgens and progestogens(testosterone,T;progesterone,P;testosterone propionate,TP;and medroxyprogesterone acetate,MPA)in water samples for the first time.Parameters influencing the extraction efficiency,such as pH of sample,salt concentration,magnetic-stirring extraction time,desorption solvent and desorption time,were investigated.Under the optimum conditions,the limits of detection(LOD)from ultra-performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)for the targets varied from 0.002 to 0.01 ng/mL.The linear ranges were in the range of 0.008 to 2 ng/mL,and the recoveries were between 80.2%and 93.9%,with relative standard deviations(RSD)ranging from 1.5%to 9.2%.The method was simple and sensitive,and could meet the analytical requirements of androgens and progestogens in environmental water samples.4.Dispersive micro-solid-phase extraction(D-μ-SPE)based on MIL-53(Al)was developed for extraction of estrogens and glucocorticoids(dexamethasone acetate,DXA;triamcinolone acetonide,TA;clobetasol propionate,CP;diethylstilbestrol,DES;estrone,E1;estradiol,E2;estriol,E3;and ethynylestradiol,EE2)in water samples.Potential factors affecting the extraction process,such as pH,ionic strength,MIL-53(Al)amount,extraction time,desorption time,desorption solvent,and the volume of desorption solvent,were studied in detail.Following D-μ-SPE,the estrogens and glucocorticoids were determined by ultra-performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS).The linearities of the target analytes were in the range of 0.005025 to 368.6 ng/mL.The detection limits(LOD)ranged from 0.0015 ng/mL to 1.0 μg/mL.And the recoveries were in the range of 80.6%～98.4%with relative standard deviations(RSD)of 4.5%～11.3%.Compared with solid-phase extraction method,this method showed obvious advantage.Furthermore,the method had other advantages of simple operation,high extraction efficiency and high sensitivity,and thus could meet the analysis requirements of glucocorticoids and estrogens in environmental water samples.5.A MIL-53(Al)mixed matrix membrane was prepared and used as a sorbent to establish a novel vortex-assisted membrane extraction method for the extraction of four estrogens(E1,E2,E3,and EE2)in urine samples.The four estrogens in urine samples were detected by high performance liquid chromatography-fluorescence detector(HPLC-FLD).Various extraction conditions were optimized,and the analytical method showed good linearity in the range of 0.02～200 ng/mL,recoveries ranging from 80.4%to 102.7%(RSD≤11.4%),and low limits of detection(0.005～1 ng/mL).The vortex-assisted membrane extraction method is a simple,accurate,and cost-effective pretreatment method,and its advantages such as good adsorption performance,simple operation,and straightforward removal and separation from solution highlight its broad utility for aqueous sample pretreatment.6.MIL-53(Al)exhibits excellent adsorption properties for estrogen.Therefore,the adsorption behaviors of MIL-53(Al)and three estrogens(E2,E3,and EE2)were investigated.The adsorption kinetics,adsorption isotherms,and adsorption thermodynamics were studied in detail and the effects of different parameters such as pH,adsorbent dosage,and salt concentration on the adsorption capacity were investigated.The results showed that the adsorption kinetics followed the pseudo-second-order kinetic model and the maximum adsorption capacities(Qm)of MIL-53(Al)for E2,E3,and EE2,obtained from the Langmuir isotherm,were 52.00 mg/g,79.43 mg/g,and 60.39 mg/g,respectively,at 298 K.Compared with Langmuir and Temkin isotherm models,the Freundlich isotherm model was thought to be the most suitable model for the present equilibrium data.In addition,these results suggest that the adsorption processes of E2,E3,and EE2 onto MIL-53(Al)were dominated by chemical adsorption.The interactions between MIL-53(Al)and the estrogens most likely originated from inter-molecular hydrogen bonding formed between-COOH in MIL-53(Al)and-OH groups in the estrogens,π-π interactions between the phenyl rings of MIL-53(Al)and estrogens,and the hydrophobic interactions occurring between the phenyl rings of MIL-53(Al)and the phenyl and alkyl rings of estrogens,as well as the breathing effect of MIL-53(Al)and van der Waals interactions formed between the MIL-53(Al)and the estrogens.Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic for all three estrogens.In addition,recycling experiments demonstrated that the used adsorbent can be reused at least 5 times for adsorptive removal following a simple washing step.Therefore,the present results confirm that MIL-53(Al)can be used as adsorptive material for the removal of estrogens from water.In conclusion,by utilizing various professional knowledge and techniques such as materials science,analytical chemistry,physical chemistry,pharmaceutical analysis,and computer science,metal-organic framework materials were successfully applied to sample pretreatment of steroid hormones in water and urine samples.In the preparation of MOFs,MIL-53(Al)was synthesized by microwave method for the first time,which shortened the reaction time,saved energy and equipment consumption,improved the synthesis efficiency,and obtained more uniform MIL-53(Al)particles.In the selection of materials,the combination of adsorption experiment method and computer simulation method is used to optimize the matching of MOFs materials and target objects,and this research strategy can avoid the blindness of material selection and facilitate the development of MOFs and their efficient use in sample preparation.In the pretreatment method,the sample pretreatment method of dispersive microsolid phase extraction,membrane protection microsolid phase extraction and the first proposed mixed matrix membrane solid phase extraction method were developed.These methods solve the shortages of large amount materials and organic solvents consume and not economical and environmental protection of solid phase extraction.In the test method,steroid hormones were detected using UPLC-MS/MS and HPLC-FLD.UPLC-MS/MS is efficient,sensitive and accurate method.However,for estrogen analysis,HPLC-FLD was more sensitive and more suitable for estrogen analysis.On the adsorption mechanism,the adsorption mechanism and action of three estrogens on MIL-53(Al)were further explored through adsorption experiments.These research results further developed the synthesis method of metal-organic framework materials,expanded the types of MOFs that can be used for pretreatment,explored the screening strategies for materials and targets,and effectively solved the limitations of solid phase extraction techniques,put forward the concept of matrix membrane,and studied the adsorption mechanism of MOFs and estrogen.These provided technical and theoretical support for the analysis and detection of steroid hormones in environmental water and urine samples,and provided effective solution for hot research issues of environmental analytical chemistry. |
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