Sharif Digital Repository

Commercial solid phase microextraction fibers posses a few drawbacks such as relatively low recommended operating temperature, instability and swelling in organic solvents, breakage of the fiber, stripping of coatings, and bending of the needle. Some of these problems have been obviated by covalent bonding of the polymer phase to the fused-silica substrate by sol-gel technology, but the easy breakage of the fiber remains a problem. In this study a new technique for preparation of unbreakable, thin and very porous fiber coatings for solid phase microextraction was proposed. In this technique firstly an intermediate film consisting ... 

During the recent years, manufactures and industries have paid attention to occupational health and safety of their employees. Formaldehyde is known as a probable carcinogenic agent and its large consumption made industries to consider it as a risk factor for occupational health. At vaccine production industries, Formaldehyde is used as disinfectant and stabilizer. In this study, a solid-phase microextraction (SPME) method based on kinetic and equilibrium calibration strategies was developed for monitoring of formaldehyde in the biologics production areas. The application and feasibility of three different sol-gel based SPME fibers with different polarities have been investigated. Two... 

The approach of this thesis is to develop and simplify robust microextraction techniques and apply these developed methods to real samples and complex matrices. Firstly, a modified solvent microextraction with back extraction method (SME/BE) combined with high performance liquid chromatography and fluorescence detection (HPLC-FD) was developed for the determination of citalopram in human plasma. Extraction process was performed in a home-made total glass vial without using a teflon ring, usually employed in SME/BE. The evaluation results demonstrated that the calibration curve showed linearity in the range of 1.0–130.0 ng/mL which covers therapeutic window and even lower amounts which is... 

Attentions to nano materials due to their vast applications in different branches of science and technology have been remarkably increased in recent years. Nanofibers are an important class of nano materials which could be used as novel sorbents because of their high surface to volume ratio as a result of long lengths and nano-to-micro-scale diameters. Electrospinning is a broadly used technology which utilizes high electrostatic forces for producing nanofibers. In this study a novel high temperature resistant solid phase microextraction (SPME) fiber was prepared besed on Polyetherimide (PEI) by this method. The porosity of the PEI fiber was investigated by scanning electron microscopy... 

In this study, ananomagnetic polyamidoamine (PAMAM) dendrimer was synthesized as a novel SPME fiber coating and implemented to the determination of traces of chlorophenols in water samples. The synthesized magnetic PAMAM shows to have many polar groups with an enhanced internal porosity which is promising to be used as an efficient extracting medium. With this purpose, a thin stainless steel wire was coated by the network of dendritic PAMAM polymer through electrolysis and chemical reactions. The synthesized fiber is physical stable since it was chemically bonded to the substrate. Extraction efficiency of new coating was investigated by headspace SPME of chlorophenols from aqueous samples... 

Polychlorinated biphenyls are a group of hydrocarbons that are composed of two benzene rings and chlorine admixture on it. Due to their special properties, these materials were added to oils for years to improve their properties. These compounds have many industrial applications in various industries, such as the production of fluorescent lamps, adhesives, dyes, and especially as a cooling and insulating liquid as the Askarel oil in power transformers. Due to the properties of these compounds, which include stability and bioaccumulation in fatty tissues, the wide use of these substances causes environmental contamination and leads to a variety of cancerous diseases. Among the cleaning... 

Sample preparation gradually becomes a major part of analysis, capable of taking up to 80% of the total time of a complete separation-based analytical process, which typically includes five steps, that is sampling, sample preparation, separation, detection and data analysis. Environmental application is a main cause driving the development of many procedures of sample preparation due to the increased public awareness that environmental contaminants are a health risk. The increased demands in the analysis of foods and natural products have brought another pressure to develop the technologies of sample preparation. The appearance of more sensitive and reliable methodology to monitor... 

This research is a bout a novel sample prepration procedure that used polypyrrole film into a stainless steel needle as a fiber coating for solid phase dynamic extraction(SPDE) with using a home-made SPDE devise and gas chromatography – mass spectroscopy for the extraction and detectionof Atrazine from the aqueous sample in direct mode of SPDE. Polypyrrole film was directly electrodeposited into the needle in a aqueous sodium dodecyl sulfonate solution with pecial set up in optimom condition of potential, time and concentration of polypyrrole. To enhance the sensitivity of the SPDE , variables affecting adsorption and desorption steps such as temperature,time,PH, flowrate and ionic strength... 

The main goal of this thesis was to develop μ-solid extraction techniques using electrspun nanofibers under the influence of magnetic field along with flow injection system. The thesis is divided into two sections:The first chapter deals with the use of magnetic field for improving μ-solid phase extraction efficiencies. After preparing the magnetic-based electrospun nanofibers (PBt/MNPs), sufficient numbers of disc from the prepared electrospun composite mat were cut and used as packing materials in a cartridge. The prepared system was coupled on-line to liquid chromatography for microextraction of selected drugs of furosemide, naproxene, diclofenac and clobetasol propionate. The homogeneity... 

In this study, a three dimensional molybdenum oxide based coordination polymer of{(M¬o2O6)(4,4'–bpy)}n was synthesized by solvothermal process. Excellent properties of the fabricated metal–organic framework such as crystallinity, porosity, sufficient thermal stability and possession of different interactions encouraged us to employ it as a novel extraction phase in sample preparation. Extraction efficiency of the MOF–based sorbent was evaluated in needle trap extraction of some chlorobenzenes as volatile aromatic organic compounds in conjugation with gas chromatography–mass spectrometry. To achieve maximum efficiency and sensitivity, influential parameters including desorption time and... 

Preparation and application of nanostructured sorbents for microextraction of some environmental pollutants and pesticides are the bases of this research. The first part of thesis deals with carbon nanotubes (CNTs) and their relevant nanocomposites using silica and conductive polymer matrix as extracting media. While, the second part involves the preparation of nanofibers and nanowires and they were applied for extraction of some selected pesticide from aquatic samples.
In the first work of part one, CNTs chemically bonded on modified gold substrate was used as novel unbreakable solid phase microextraction fiber for isolation of diazinon and fenthion, as model compounds. Parameters... 

In this study different kinds of solid phase microextraction fibers based on sol-gel technology were employed for extraction and pre-concentration of phenol in occupational air and oxadiargyl in plant and environmental samples. In the first work, a SPME method followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) was developed for the analysis of phenol in the air. The application and feasibility of three different sol-gel based SPME fibers with different polarities, polar and non-polar poly (dimethylsiloxane) (PDMS) and polyethylene glycol (PEG), have been studied. Influential parameters such as fiber coating type, type of derivatization reagent,... 

In this study, the SPME nanocomposite coating of metal organic framework/polyaniline (MOF/PANI) was fabricated by the electrochemical polymerization process. Its application was investigated via extraction of chlrobenzenes from head-space aqueous solution. The power supply voltage, time of deposition and the percent of added MOF to main polymer solution was investigated and optimized in the electrochemical polymerization process. Also extraction parameters influencing the extraction efficiency including ionic strength, extraction temperature, extraction time, as well as desorption temperature and time were investigated and optimized. The detection limits of the developed method under... 

Novel electrospun nanofibers and their applications as the microextractionsorbents are the centre of this research. Polymeric nanofibers with diameter in the scale of nano-to-micro were prepared by the electrospinning method and employed for microextraction purposes. Two major microextraction methods included solid phase microextraction (SPME) and micro-Solid phase extraction (µ-SPE). In the first work, a novel SPME fiber was fabricated by electrospinning method. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three... 

In the first work, a superhydrophobic polystyrene hollow fiber (PS–HF) was synthesized by electrospinning and used in microextraction of trazine herbicides from aquatic media followed by gas chromatography mass spectrometric (GC–MS) determination. Effects of different parameters influencing the extraction efficiency including the solvent extraction and its amount, the desorbing solvent and its amount, extraction time and ionic strength were optimized. The characteristic properties of the hollow fiber were studied by scanning electron microscopy (SEM). The limits of detection and quantification of the method under optimized condition were 2 and 6 ng L-1, respectively. The relative standard... 

The purpose of this study was to investigate the capability of Isotopic Ratio Mass Spectrometry (IRMS) in the detection of four common natural plant frauds in saffron, namely Marigold flower, Safflower, Rubia and Saffron Style. For this purpose, first natural saffron isotopes were analyzed and used to investigate fingerprints of carbon-13 and nitrogen-15 isotopes by Elemental Analyzer Isotopic Ratio Mass Spectrometry (EA-IRMS) and carbon-13 isotopic ratio of saffron components by Gas Chromatography Isotopic Ratio Mass Spectrometry (GC-C-IRMS). Then, according to the isotopic behavior of the original saffron, they were sampled to form a mixture of saffron that is representative of the... 

In this study, a new resorcinol-formaldehyde xerogel was synthesized based on sol-gel technology and employed as a sorbent for micro solid phase extraction (µ-SPE) of BTEX and some selected pesticides from aqueous samples.
In the first part, a µ-SPE method in combined with headspace solvent microextraction (HS-SME) along with gas chromatography- mass spectrometry detection (GC–MS) was developed for the analysis of BTEX in aqueous samples. In our knowledge, this is for the first time that these two different extraction methods has been coupled to maximize the advantage of each extraction method. Influential parameters such as the peristaltic pump flow rate, extraction volume, extraction... 

The main approach of this thesis is the study of metal- organic frameworks (MOFs) performance as extractive phases in sample preparation methods. Hence, various MOFs were synthesized to investigate the roles of sorbent properties such as surface areas, pore sizes and shapes, interaction types, bonds and building units in extraction procedures of analytes. The prepared sorbents in conjugation with gas chromatography- mass spectrometry (GC-MS) were applied to determination of the environmental pollutants like chlorobenzenes, benzene derivatives (BTEX), polyaromatic hydrocarbons (PAHs) and residues of agriculture herbicides.In the first work, considering studying the roles of the sorbent pore... 

In recent years, chromatographic techniques as one of the most important analytical techniques have been greatly developed from instrumentation and data volume point of views. On the other side, multivariate curve resolution (MCR) techniques as a branch of chemometrics have potential for the analysis of multivariate and huge data sets. In addition, MCR methods have been developed very fast in these years and their potential have been shown in the analysis of different types of chemical data. Thus, combination of sophisticated chromatographic techniques (e.g. gas chromatography-mass spectrometry (GC-MS) or comprehensive two-dimensional gas chromatography (GC×GC)) with MCR techniques can be... 

In this research, Cu-TATAB/Polyurethane (PU) nanocomposite fibers were prepared via electrospinning method in order to increase the overall extraction efficiency. The incorporation of Cu-TATAB, as a metal organic framework (MOF), in the synthesized nanocomposite contributed to the enhanced efficiency. The prepared sorbent was implemented for the thin film microextraction (TFME) of organochlorine species and their determination was subsequently performed by gas chromatography-mass spectrometry (GC-MS). To achieve the maximum efficiency of the synthesized sorbent, the parameters of MOF percentage in nanocomposites, solvent type and volume, desorption time, solution ionic strength and...