Dynamic Magnetic Field Assisted Active Solid Phase Extraction And Pharmaceutical Analysis In The Environment

Along with the development of the pharmaceutical industry,the use of drugs in various fields,including medicine and livestock,releases many drug residues into our environment.The residues of drugs in water and food may lead to drug resistance and other side effects on humans,including liver damage,and gastrointestinal disturbances.However,the analysis of these residues in environmental water or food has a very low concentration and a complicated matrix,so it is important to establish a method for accurately analyzing it.Although the analysis step can be classified in various ways,it can be divided into three major steps,namely,sample collection,sample pretreatment,and instrumental analysis.Here,the sample pretreatment process is very important in analysis.In general,natural samples are a mixture of many kinds of different amounts substances,and it is not an exaggeration to say that accurate analysis of a target substance with high sensitivity depends entirely on the sample preparation process.a lot of sample pretreatment methods have been studied and introduced into practice,and their superiority has been proven.Solid phase extraction is one of the sample pretreatment methods for selectively extracting a target substance from a matrix,and research on it has been deepened over the past decades,and many types of solid phase extraction methods have been studied and commercialized.However,each method has several flaws along with its characteristics.For example,in solid phase extraction,there are advantages such as high sample throughput,high selectivity,and simple use,but there are defects such as a large amount of adsorbent and solvent required and deferment of analysis time due to internal pressure.So evaporation of the desorption solvent is required to increase the enrichment factor(EF),and there is a weakness in that it is not suitable for realizing on-line analysis.In this dissertation,by synthesizing an adsorbent using the surface modification of magnetic particles and controlling the motion of the magnetic adsorbent according to the control of the dynamic magnetic field,the research results were obtained that could overcome the defects in solid-phase extraction and improve the analysis characteristics.The proposed method was successfully applied to the determination of 6 tetracyclines and 5 flavonoids,which exist in a water and onion sample,to achieve a low LOD,good linearity range,and reliable accuracy and precision.The main work and achievements of this dissertation are outlined as follows.1.A reciprocating magnetic-field-assisted on-line solid-phase extraction(RMF-SPE)method coupled with liquid chromatography-tandem mass spectrometry(LC-MS/MS)has been developed for continuous enrichment of trace chemicals in samples.Under the assist of the reciprocating magnetic field,modified magnetic nanoparticles were applied to prepare microcolumn with even dispersion by periodical motion,instead of traditional compaction as extraction sorbents.When sample passed through the extraction region,dynamic sorbents generates an advantage of countless contacts between sorbents and targets without blocking for high efficient extraction.In classical solid phase extraction,the generation of internal pressure could not be avoided because the adsorbent was packed densely in the column.In this study,since the adsorbent was dispersed inside the column and the continuous reciprocating motion was maintained by the external reciprocating magnetic field,the generation of internal pressure was eliminated and high adsorption efficiency was achieved.2.Theoretical study and simulation were conducted on the motion of adsorbent particles with magnetic properties inside the column by a strong external reciprocating magnetic field.Under reciprocating magnetic field,magnetic nanoparticles move in a sensitive manner resulting in great improvement of uniformity of the MNPs distribution in the microflow system.3.The surface characteristics and magnetic properties of magnetic adsorbents modified with a carboxyl group and boronic acid were characterized using TEM,IR,XPS,and XRD.It has the potential to significantly improve sorption selectivity and sorption efficiency by specific interactions(hydrophobic interactions,electrostatic interactions,etc.)between specific functional groups on the surface of sorbent and targets.4.As factors affecting extraction by the proposed method,pH,magnet reciprocating speed,sample flow rate,amount of sorbent,amount of elution solvent,elution time,and elute composition were selected.The optimized conditions are as follows in relation to two targets,respectively;pH;7,9,reciprocating speed;250 rpm,sample flow rate;2 mL min-1,amount of sorbent;10mg,amount of elution solvent;100μL,elution time;20min,10min,elute composition;methanol/acetonitrile/0.02 mol L-1 oxalic acid(10:20:70,v/v)solution,methanol/formic acid(95:5,v/v)solution.5.Magnetic particles modified with carboxyl groups were synthesized,and the residual amount of six antibiotics in environmental water(tap water,river water,sewage water)was analyzed using these magnetic particles as adsorbents.The method showed high relative recovery(95.4-111.1%)and good repeatability with RSD from 2.9 to 11.8%for the 200 mL water sample.The linearity range,limits of detection(LODs),and limits of quantification(LOQs)were 0.5-200 μg L-1(chlortetracycline)and 0.1-200 μg L-1(other TCs),12.0-74.1 ng L-1,and 40.1-247 ng L-1,respectively.6.Boric acid-modified magnetic particles were synthesized and the five flavonoid contents in onion were analyzed using it as an adsorbent.Under optimal conditions,the proposed approach has a wide linear dynamic range and good linearity(daidzin and wogonoside 50-1000 μg L-1,other flavonoids 10-1000 μg L-1),low detection limits(1.86-14.2 μg L-1),limits of quantification(5.52-47.6μg L-1),and satisfactory recovery(94.9-106.2%).provided.Depending on the target,it can be applied to various purposes by using an adsorbent with the necessary properties,and by replacing a permanent magnet with an electromagnet,the device can be simplified.If necessary,the adsorption column can also be used as a elution column to simplify operation.In the future,it is expected that this sample pre-treatment technique will play a part in the sample preparation for the analysis of ultra trace substances in the environment and food.