Preparations Of Novel Electrospun Nanofibers And Their Applications In Sample Pretreatment

Since 2006,a novel liquid phase microextraction technique was introduced,dispersive liquid-liquid microextraction(DLLME),which has attracted much attention due to the merits of small amount of solvent,short extraction time,ease of operation,as well as high enrichment factors for analytes.Among the whole DLLME process,transferring the organic drop is a very important but difficult step.Based on this,many researchers have proposed different phase transferring methods,but each method has its limitations of usage.Thin film microextraction(TFME),a new format of SPME,not only has the advantages of conventional SPME,but also possesses more outstanding advantages,large surface area-to-volume ratio results in obtaining extraction equilibrium in short time and increasing the extraction capacity.And this technique has been applied for the determinations of varieties of compounds.Recently,many researchers paid much attention to exploring new formats or new TFME adsorbents materials for more wide applications.Electrospinning is a versatile technique that relies on repulsive electrostatic forces to draw a viscoelastic solution into nanofibers that is not easily achievable with other conventional fiber-forming technique.The diameters of fabricated ultrafine fibers range from submicrons to nanometers.The electrospun fibers usually exhibit excellent attributes including easy preparation,cost effective,large surface to volume ratios and high porosities,which have made them gain much value for varieties of applications.In this work,two different kinds of nanofibers were prepared successfully through a facile electrospinning strategy,polystyrene nano fiber and polystyrene/metal organic framework-199 composite nanofiber.Based on the nano fibers a new phase transfer method of DLLME and a new TFME-HPLC method were established,respectively.At last,these proposed methods were applied to determine aldehydes in real samples.The main contents are as follows:1.The aim of this work is to find a new method to transfer the organic phase following dispersive liquid-liquid microextraction(DLLME)for sample analysis.For this,polystyrene(PS)nanofiber was prepared through electrospinning,which was the first time used as the adsorbent to transfer the organic phase following DLLME procedures for high performance liquid chromatography(HPLC)analysis.The nanofiber was characterized to have a good knowledge for experiment research,chemical stability and super hydrophobicity enable the fiber adsorbing the organic drop well without water,large porosity and satisfactory specific surface area provide high adsorption capacity.Under the optimal conditions,the developed method applying the determination of aldehydes in water provided good linearity and wide linear ranges.The detection limits of aldehydes were between 1.4 and 4.6 nmol L-1,satisfactory reproducibility(2.9-14.4%)and acceptable recovery(92-114%)were obtained.As a result,the developed method was successfully applied to the analysis of aldehydes in environmental water.The merits of this approach include convenience,low cost,and satisfactory sensitivity.It provides a potential way for fast and convenient transferring the organic drop in DLLME procedure.2.In this work,polystyrene/MOF-199(PS/MOF-199)nanofiber was synthesized by electrospinning,and a novel thin film microextraction-high performance phase chromatography method(TFME-HPLC)was introduced and applied for the determination of aldehydes in human urine.Some features of the electrospun nanofiber were characterized,including satisfactory morphology,porous fibrous structure,large surface area,good solvent stability,high hydophobicity and good extraction efficiency.Some experimental conditions that may affect the extraction performance were also studied.Under the optimal conditions,the established TFME-HPLC method exhibited good linearity and wide linear range with correlation coefficients(R2)ranging from 0.9943 to 0.9991,and the limits of detection(LODs)were at the range of 4.2 nmol L-1-17.3 nmol L-1.Relative standard deviations(RSD,n=5)ranged from 2.1%to 13.3%,the recoveries of aldehydes varied from 82%to 112%at spiked concentration level.Then this proposed approach with the advantages of simplicity,rapidity,cost-effective,sensitivity and non-invasion was successfully applied to determining aldehydes in human urine.