The Preparation And Application Of Novel Stir Bar Sorptive Extraction Coatings And Devices

Traditional sample preparation techniques such as liquid-liquid extraction(LLE)and soxhlet extraction consume large amounts of organic solvent and often require complex time-consuming multi-step procedures which can lead to low accuracy,contamination and losses of analytes.Modern trends in analytical chemistry are toward the simplification,miniaturization and low-consumption of organic solvent and sample volumes.Stir bar sorptive extraction(SBSE)which was developed in 1999 is such a novel microextraction technique.This technique has the similar extraction mechanism to that of solid phase microextraction(SPME).The main difference between SPME and SBSE is that SBSE employed about 50-250 times larger volume of extraction phase than SPME,resulting in higher recoveries and higher sample capacity.In recent years,SBSE has been successfully applied for organic substances analysis and elemental speciation in environmental,food and biological samples.However,as the time from its emergence to now is only about ten years,it still has some limitations or drawbacks.For examples,types of commercially available SBSE coatings are very limited;it lacks those coatings with high selectivity,high extraction efficiency,robust and better affinity to polar compounds;it is unsuitable for field analysis or sampling of environmental water and air samples and so on.The aim of this dissertation is to prepare new polar SBSE coatings and establish SBSE-high performance liquid chromatography(HPLC)-inductively coupled plasma mass spectrometry(ICP-MS)methods for trace elemental speciation analysis;to design a portable SBSE sampling device and employ it for off/on-site SBSE of PAHs in environmental waters;to develop new SBSE extraction mode for direct analysis of complex water samples.The major contents of this dissertation are described as follows:(1)A newly high polar extraction phase of titania immobilized polypropylene hollow fiber(PPHF-TiO2)was prepared by sol-gel immersion and low temperature hydrothermal process.With a suitable size of stainless steel magnetic bar inserted into the prepared PPHF-TiO2,a disposable PPHF-TiO2 coating stir bar was obtained.The prepared PPHF-TiO2 was characterized by X-ray diffraction spectrometry and scanning electron microscopy,and the significant parameters affecting the extraction efficiency of different arsenic species were studied.Based on the above facts,a new method of SBSE combined with HPLC-ICP-MS was developed for the speciation of phenyl arsenic compounds and their possible transformation products in chicken tissues.Under the optimal conditions,limits of detection(LODs)of the developed method for eight target arsenic species were in the range of 11.4-64.6 ng L-1 with enrichment factors(EFs)of 8.5-22.3 fold(theory EF was 50 fold),and the relative standard deviations(RSDs)were varying from 6.3 to 12.6%(n=7).The proposed method was successfully applied to the speciation analysis of arsenic in certified reference material of BCR-627 tuna fish tissue and chicken meat/liver samples with satisfactory results.The PPHF-TiO2 was demonstrated to be a highly selective coating for the target arsenic species,and could be easily prepared in batches with low cost.In addition,with the disposable coating,the carry-over effect commonly encountered in conventional SBSE was avoided.(2)High polar organic-inorganic hybrid SBSE coating of partially sulfonated polystyrene-titania(PSP-TiO2)was prepared by sol-gel and polymer blend techniques.PSP-TiO2 hybrid coating overcomes the swelling of PSP and spalling of TiO2 by the complementation of good film formation property of PSP and high mechanical strength of TiO2.With PSP-TiO2 hybrid material as the extraction coating,a new method of SBSE combined with HPLC-ICP-MS was established for the analysis of seleno-amino acids and seleno-oligopeptides(Selenomethionine(SeMet),Selenoethionine(SeEt),Methylseleno-cysteine(MeSeCys),Selenocystine(SeCys2),selenodiglutathione(GS-Se-SG),y-glutamyl-Se-methyl-selenocysteine(y-GluMeSeCys))in biological samples.The LODs were in the range of 50.2-185.5 ng L-1(77Se)and 45.9-158.8 ng L-1(82Se)with the RSDs within 4.9-11.7%and the EFs of 16.4-51.0(theory EF was 66.7)for the target selenium species.The method was used for the analysis of certified reference material SELM-1 selenium enriched yeast,human urine and garlic samples.Different from the conventional organic polymer SBSE coatings(such as polydimethylsiloxane,PDMS),the prepared PSP-TiO2 coating can be used to directly extraction seleno-amino acids based on the cation exchange interaction without derivatization,which provides a new idea for the SBSE analysis of polar compounds.(3)C18coated stir bar was prepared by adhering C18-silica particles onto the glass stir bar with PDMS sol,and a simple,fast and non-derivatization C18-SBSE-HPLC-ICP-MS method for the determination of monobutyltin trichloride(MBT),dibutyltin dichloride(DBT)and tributyltin chloride(TBT)in water and sediment samples was established.The factors affecting on extraction of three butyltin species by C18-SBSE were systematically studied.Under the optimal conditions,the LODs of the proposed method for three butyltins were in the range of 15.6-29.4 ng L-1 with the linear range between 0.05/0.1-50 ?g L-1,and the EFs were 85-127 fold(theoretical EF was 200 fold).The preparation reproducibility of C18-stir bar was 5.6-11.8%in the same batch(n=7)and 12.8-15.4%(n=7)in the different batches,and reuse times were above 25.Besides,HPLC separation of butyltins was studied,and quick separation(<10 min)was accomplished by using a mobile phase of water-methanol-formic acid(76:16:8,v/v)at a flow rate of 1.5 mL min-1,which was compatible with the conventional ICP-MS detector without addition of oxygen gas or desolvating systems.(4)Polyethyleneglycol(PEG)/hydroxy polydimethylsiloxane(OH-PDMS)/y-mercaptopropyl trimethoxysilane(y-MPTS)coated stir bar was prepared by sol-gel process and the proportion of coating components were optimized by orthogonal test.The preparation reproducibility in the same batch and between different batches were 3.3-14.3%(n=5)and 7.7-16.6%(n=3),respectively.The prepared PEG/OH-PDMS/y-MPTS stir bar could be reused for more than 20 times.This mixed coating stir bar showed a good extraction performance to the different compounds iodine containing.Based on this fact,a novel method of SBSE-HPLC-UV for the analysis of amphoteric thyroxines(3,3',5,5'-tetraiodothyronine(T4),3,3',5-triiodothyronine(T3),reversed-3,3',5-triiodothyronine(rT3))and their metabolite 3,5-diiodothyronine(T2)in real pharmaceutical formulation and human urine samples was developed.The influencing factors of SBSE,such as desorption solution,sample pH,extraction time,desorption time,stirring rate and salt effect were studied in detail,and the analytical performance of the proposed method was evaluated.Compared with solid phase extraction and LLE methods,higher sensitivity(0.13-2.73?g L-1)and EFs(14.9-70.4 fold,theoretical EF was 100 fold)were obtained.(5)Battery-operated portable SBSE sampling device which integrated the sampling and sample pretreatment into a single step was designed and its applicability in off/on-site sampling was evaluated by PDMS coating SBSE-HPLC-fluorescence detection(FLD)analysis of six polycyclic aromatic hydrocarbon compounds(PAHs)in environmental waters.The self-made portable SBSE sampling device is simple,easy-to-operate,user friendly,low cost,easy-to-commercialize,and can be processed in direct immersion,headspace extraction and continuous flow extraction modes.Since the coating stir bar was fixed onto the portable device by magnetic force,it is very convenient to install,remove and replace the stir bar,and the coating friction loss which occurred frequently in conventional SBSE process could be avoided.The parameters affecting the extraction of six PAHs by the self-made portable SBSE sampling device with different sampling modes were studied and the analytical performance of the portable SBSE-HPLC-FLD method was evaluated.The proposed portable PDMS-SBSE-HPLC-FLD method was applied for the analysis of six PAHs in East Lake water,and the analytical results obtained by on-site SBSE sampling were in good agreement with that obtained by off-site SBSE sampling,demonstrating that the designed portable SBSE device was feasible for the field sampling.(6)With a porous membrane wrapped around the coated stir bar,a novel extraction mode of SBSE termed as membrane protected SBSE(M-SBSE)was proposed.During the extractions,the low molecular weight target analytes could diffuse freely through the membrane pores and reach the surface of stir bar coating while the high molecular weight interferences(such as humic aicd)are blocked by the membrane.By combining M-C18-SBSE with HPLC-UV,a method for the analysis of two common nonsteroidal antiinflammatory drugs Ketoprofen and Naproxen in complex water samples was established.The significant parameters affecting the extraction efficiency of M-C18-SBSE were studied and the analytical performance was evaluated.The developed method was successfully applied to the analysis of Ketoprofen and Naproxen in domestic sewage and campus lake water samples.M-SBSE could be applied to direct analysis of complex water samples without filtration,centrifugation and other steps.Besides,the friction loss of SBSE coating was effectively avoided.