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Metal-organic Frameworks for Solid-phase Extraction in the Sample Pre-treatment Technology

Author: YangShaoLei
Tutor: YaoShouZhuo
School: Hunan University
Course: Analytical Chemistry
Keywords: Sample pre-treatment Solid-phase extraction Metal-organicframeworks Zeolitic imidazolate frameworks Polycyclic aromatichydrocarbon Perfluorinated compounds Synthetic pyrethroids
CLC: O658.2
Type: Master's thesis
Year: 2013
Downloads: 109
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Abstract


Metal-organic frameworks (MOFs) are a novel class of inorganic-organiccrystalline materials, which have large specific surface areas, fascinating structures,high thermal and chemical stability. The solid-phase extraction is one of the mostenergetive method in the field of separation science (such as environmental, food,clinical, pharmaceutical and industrial chemistry, etc.). The methodology continues toevolve, through found and usable of new sorbents, in response to the desire to simplifythe sampling process and clean-up the target analytes in complex matrices. In thisdissertation, metal-organic frameworks (MOFs) are utilized as stationary phases forsample pre-treatment. The novel aspects of this dissertation are summarized asfollows:1. Uniformed metal-organic framework5was synthesized at room temperatureand characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction(XRD) pattern and scanning electron microscopy (SEM). The prepared material wasused as an adsorbent of solid-phase extraction for the pre-concentration of polycyclicaromatic hydrocarbons (PAHs) in water samples combined with high-performanceliquid chromatography for the first time. Although MOF-5is unstable and changedpartly when exposed to water, it is still demonstrated that the derived material ofMOF-5is a good sorbent for water samples due to the strong π-π conjugate effectbetween the framework terephthalic acid molecules and PAHs, and the π-complexationbetween PAHs and the central metal ions of MOF-5. Under the optimized experimentalconditions, good sensitivities were achieved with low LODs ranging from0.4to4.0ngL1, recoveries in the range of80.2-120.2%and RSDs less than11.7%for theinvestigated polycyclic aromatic hydrocarbons.2. Zeolitic imidazolate frameworks were synthesized fast at room temperatureunder aqueous conditions and utilized as stationary phases to extract perfluorinatedcompounds (PFCs) in water samples combined with high-performance liquidchromatography coupled with mass spectrometry (HPLC-MS). The synthesis wassimple, convenient and environmental-friendly because it was seccessfully used assolvent instead of organic solvent. The material has potential applications forpersistent organic pollutants in environmental samples due to its high surface area,strong hydrophobicity and remarkable stability. The solid-phase extraction (SPE) conditions affecting the extraction effciency were optimized, including sample volume,ionic strength, eluent and its volume. The results indicated that the method was reliablewith low detection limit, high sensitivity and good repeatability. The new material wasfound to be applied for determination of perfluorohexanoic acid (PFHA),perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid potassium salt(PFOS) in water samples.3. A sample preparation method has been developed to analyse syntheticpyrethroids from environmental samples by zeolitic imidazolate frameworks/chitosancomposites which were prepared in the chitosan hydrogels. Owing to the uniquestructural characteristic of the composite material and the hydrophilic property ofchitosan, the procedure is rapid and efficient for extracting trace pesticides from water.A comprehensive study of the adsorption conditions such as extraction rate, solvent fordispersion, and organic modifier was presented. Under the optimized conditions, goodlinearity and low limits of detection of0.01-0.15ng L-1were obtained. The analysis ofpesticides in real water samples gave satisfactory recoveries ranging from79.20-116.28%.

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CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Separation of elements and compounds > Extraction method
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