Sharif Digital Repository

A homemade immersed solvent microextraction (SME) device was successfully developed for the trace enrichment of phenols from aqueous samples. A microdrop of butyl acetate was suspended from the tip of a microsyringe needle, immersed in an aqueous spiked solution for a preset time. The microdrop was then retracted into the microsyringe and injected directly into a gas chromatography-mass spectrometry (GC-MS) injection port. Effects of different parameters such as the type of solvent, extraction time, stirring rate, and temperature were investigated and optimized. To reduce the polarity of phenols and prevent tailing effects, all the phenols were derivatized prior to extraction using acetic... 

A simple and rapid method for simultaneous separation and preconcentration of ultra-trace amounts of nitrate and nitrite using in-syringe liquid microextraction is developed. The extraction procedure is based on the selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine in 100 μL of 1-butyl-3-methylimidazolium hexafluorophosphate as an extracting phase within a syringe. The atomic-absorption signal of copper in the ionic liquid layer is proportional to the nitrate and nitrite concentrations. When barbituric acid is used, nitrite is converted into violuric acid and thus it is removed from the environment. In this case, the selectivity of the modified-ligand is... 

Polyhedral oligomeric silsesquioxanes are 3D nanoscaled materials with large potential in solid phase microextraction (SPME). Here, as a case study, an octaglycidyldimethylsilyl modified polyhedral oligomeric silsesquioxane network is described. It was deposited on a stainless steel wire via a sol–gel method and used as a fiber coating for SPME of aromatic compounds. The uniform pore structure, high surface area, and hydrophobicity of the network make it susceptible toward isolation of non-polar and semi-polar chemical compounds. The performance of the fiber coating was tested with three classes of environmental pollutants, viz. chlorobenzenes (CBs), benzenes (benzene, toluene, ethylbenzene,... 

A high-temperature-resisant solid-phase microextraction (SPME) fiber was prepared based on polyetherimide (PEI) by the electrospinning method. The PEI polymeric solution was converted to nanofibers using high voltages and directly coated on a stainless steel SPME needle. The scanning electron microscopy images of PEI coating showed fibers with diameter range of 500-650 nm with a homogeneous and smooth surface morphology. The SPME nanofibers coating was optimized for PEI percentage, electrospinning voltage, and time. The extraction efficiency of the coating was investigated for headspace SPME of some environmentally important polycyclic aromatic hydrocarbons from aqueous samples followed by... 

Conductive polymers (CPs) are classified as materials which exhibit highly reversible redox behavior and the unusual combined properties of metal and plastics. CPs, due to their multifunctionality, ease of synthesis and their stability, have attracted more attentions in different fields of research, including sample preparation. CPs along with several commercial hydrophilic sorbents, are alternative to the commercially available hydrophobic sorbents which despite their high specific surface areas, have poor interactions and retentions in the extraction of polar compounds. This review covers a general overview regarding the recent progress and new applications of CPs toward their synthesis... 

A new technique is introduced for preparation of an unbreakable fiber using gold wire as a substrate for solid phase microextraction (SPME). A gold wire is used as a solid support, onto which a first film is deposited that consists of a two-dimensional polymer obtained by hydrolysis of a self-assembled monolayer of 3-(trimethoxysilyl)-1-propanthiol. This first film is covered with a layer of 3-(triethoxysilyl)-propylamine. Next, a stationary phase of oxidized multi-walled carbon nanotubes was chemically bound to the surface. The synthetic strategy was verified by Fourier transform infrared spectroscopy and scanning electron microscopy. Thermal stability of new fiber was examined by... 

A method based on immersed solid-phase microextraction (SPME) and gas chromatography mass spectrometry detection (GC-MS) for the determination of organophosphorous pesticides (OPPs) in aqueous samples was developed. A sol-gel based coating fiber was prepared using 3-(trimethoxysilylpropyl) amine as precursor. The synthesized fiber was prepared in a way to impart polar moiety into the coating network and would be more suitable for extracting polar and semi-polar organic pollutants. Important parameters influencing the extraction process were optimized and an extraction time of 40 min at 30 °C gave maximum peak area, when NaCl (20% w/v) was added to the aqueous sample. The linearity for... 

We describe a nanocomposite prepared from polydopamine, silver nanoparticles, and polypyrrole (PDA-Ag-PPy) that can be used for the microextraction in packed syringe (MEPS) of tricyclic antidepressants from urine samples. The PDA-Ag-PPy composite was prepared in-situ by the reduction of silver ion - doped PPy during oxidative polymerization of dopamine. The PDA-Ag coatings on the nanoribbon – shaped PPy represent a highly porous, inorganic–organic hybrid nanomaterial that has a wide range of applications. The nanocomposite was characterized by FTIR and scanning electron microscopy. It is shown to be an efficient sorbent for the MEPS of the tricyclic antidepressants amitriptyline, imipramine... 

In this research, three fibers including cellulose acetate (CA), CA–phenyltriethoxysilane (PTES) prepared via sol–gel electrospinning and sol–gel–based CA fibers immersed in PTES solution (dipped–CA–PTES) were prepared. The composition and morphology of the prepared fibers were evaluated by energy dispersive X-ray spectroscopy and field emission scanning electron microscopy. The prepared fibers were implemented in a home–made needle trap device, followed by thermal desorption of the selected chlorobenzenes (CBs) to a gas chromatography–flame ionization detector. Finally, parameters affecting the extraction methodology such as the amount of sorbent, extraction time and temperature, desorption... 

Three-dimensional (3D) polyamide scaffolds were fabricated by applying a solvent bath as the collecting element. Electrospun nanofibers were immersed into the solvent bath to give a material with a laminated 3D texture. In parallel, 2D nanofibers were synthesized and utilized as microextractive phases in a needle trap device to compare the capabilities of 2D and 3D materials in terms of headspace extraction of various chlorobenzenes (chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,3,4-tetrachlorobenzene). The results demonstrate the superiority of 3D nanofibrous scaffolds over 2D mats. The porosity, morphology, and thermal stability of the 3D scaffolds... 

This work introduces a new gradient fiber coating for microextraction of chlorobenzenes. Nanoclusters of organoclay-Cu(II) on a copper wire were fabricated by wireless electrofunctionalization. The resultant gradient coatings are more robust, and thermally and mechanically stable. Wireless electrofunctionalization was carried out in a bipolar cell under a constant deposition potential and using an ethanolic electrolyte solution containing stearic acid and montmorillonite. Stearic acid acts as an inexpensive and green coating while montmorillonite acts as a modifier to impart thermal stability. The gradient morphology of the nanoclusters was investigated by scanning electron microscopy,... 

A superhydrophobic extractive phase was prepared and packed in a needle trap microextraction device for extraction of volatile organic compounds, followed by their determination by gas chromatography. The superhydrophobic phase was prepared by surface modification of melamine formaldehyde (MF) sponge embedded by reduced graphene oxide (rGO). The overall properties of the modified MF along with its high sorption capacity and low cost fabrication were indicative of its feasibility to be highly suitable for extraction of organic pollutants. The determined water contact angle (>150o) from the surface of melamine formaldehyde–reduced graphene oxide (MF–rGO) revealed its high affinity toward... 

A modified in-tube solid phase microextraction (SPME) technique in conjunction with a high performance liquid chromatography (HPLC) was developed for the trace determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction device contained a regular HPLC syringe, replacing the metallic needle by two concentric fused silica capillary tubes. The capillary tubes were coated with polydimethylsiloxane (PDMS) as the sorbent and were attached to the syringe by a homemade interface made from polyether ether ketone (PEEK). The sorption of analytes was achieved by frequent withdrawing and ejecting the water sample from/into a vial via the capillary tubes. For the desorption... 

Sol-gel based solid-phase microextraction fibers supported by a stainless steel wire were fabricated and employed for GC-MS determination of oxadiargyl in real samples. The fibers were based on four compounds with different polarity: polar and non-polar (end-capped) poly(dimethylsiloxane) (PDMS), polyethylene glycol (PEG), and poly(ethylene-propyleneglycol)-monobutyl ether (UCON). For this purpose, the surface of the stainless steel was initially modified by (3-mercaptopropyl) trimethoxysilane. The results of the modification procedure were evaluated by cyclic voltammetry and energy dispersive X-ray (EDX) spectroscopy. After the modification, four different sol-gel based SPME fibers with... 

A novel solid-phase microextraction(SPME) fiber was prepared using sol-gel technology with ethoxylated nonylphenol as a fiber coating material. The fiber was employed to develop a headspace SPME-GC-MS method suitable for quantification of 13 polycyclic aromatic hydrocarbons (PAHs) in water samples. Surface characteristics of the fibers were inspected by energy dispersive X-ray (EDX) spectroscopy as well as by scanning electron microscopy (SEM). The SEM measurements showed the presence of highly porous nano-sized particles in the coating. Important parameters affecting the extraction efficiency such as extraction temperature and time, desorption conditions as well as ionic strength have been...