Sharif Digital Repository

A new and convenient format of single drop microextraction (SDME) was developed and applied for isolation of some selected aryloxyphenoxypropionate herbicides from aquatic media. In contrast to the conventional SDME procedure, in this set-up the extraction microdrop was positioned at the bottom of a conical vial in order to provide much higher stability for the organic extraction phase while a magnetic bar was used for stirring the aqueous solution. A simple magnet was used for positioning the bar on the top of the microdrop prior to stirring. The whole set-up led to the use of any volume of extraction solvent with unlimited stirring rates. Some important extraction parameters such as the... 

An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of aryloxyphenoxypropionate herbicides from aquatic media. A microdrop of toluene was used as the extraction solvent. Some important extraction parameters such as type of solvent, solvent dropsize, stirring rate, ionic strength and extraction time were investigated and optimized. The microdrop volume of 1.5 μL, a sampling time of 25 min, and use of toluene were major parameters for achieving high enrichment factors. The linearity was studied by preconcentration of 4 mL of the water samples spiked with a standard solution of aryloxyphenoxypropionates at the concentration range of 0.15 to 30 ng... 

A novel method based on microextraction in packed syringe (MEPS), as a sample preparation technique in combination with gas chromatography-mass spectrometry (GC-MS) was developed using a polypyrrole (PPy) nanowires network as the extracting medium. The PPy nanowires network was prepared using a soft template technique and its characterization was studied by scanning electron microscopy (SEM). The use of micelles in this methodology has an important role in the shape of the growing polymer. The pyrrole monomer was introduced into cetyltrimethylammonium bromide (CTAB) micelles and this has led to the formation of nanowires with diameters ranging from 30 to 60 nm. The bulk PPy prepared without... 

A highly efficient polybutylene terephthalate (PBT)-based nanocomposite containing nickel oxide nanoparticles was synthesized by electrospinning technique and used as a fiber coating for solid phase microextraction. The influential morphological parameters and capability of the prepared nanocomposite including the NiO content, the coating time, the PBT concentration and applied voltage were considered for optimization. The applicability of the synthesized fiber coating was examined by headspace solid phase micro extraction and gas chromatography mass spectrometry detection of some volatile organic compounds in aqueous samples. Among the synthesized nanocomposites and pristine PBT nanofibers,... 

A novel method based on microextraction in packed syringe (MEPS) as sample preparation technique coupled off-line with gas chromatography-mass spectrometry was developed using electrospun nanofibers as sorbent. For electrospinning of polypyrrole/polyamide-based nanofiber, a homogeneous solution containing nylon 6, ferric chloride and pyrrole monomer was prepared and then was drawn into a 2.5-mL syringe. By applying a voltage of 13akV between the needle of the syringe and an aluminum-foil collector, the nanofibers could be formed on the surface of the collector. The prepared sheet was used as the sorbent for MEPS to analyze some selected organophosphorous pesticides. Important parameters... 

A nanocomposite of silica-polydiphenylamine doped with silver nanoparticles (Ag-SiO2-PDPA) was successfully synthesized by the sol-gel process. For its preparation, PDPA was mixed with butanethiol capped Ag nanoparticles (NPs) and added to the silica sol solution. The Ag NPs were stabilized as a result of their adsorption on the SiO2 spheres. The surface characteristic of nanocomposite was investigated using scanning electron microscopy (SEM). In this work the Ag-SiO2-PDPA nanocomposite was employed as an efficient sorbent for micro-solid-phase extraction (μ-SPE) of some selected pesticides. An amount of 15 mg of the prepared sorbent was used to extract and... 

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM) was applied to the determination of methyl tert-butyl ether (MTBE) in water samples. The effect of main parameters affecting the extraction efficiency was studied simultaneously. From selected parameters, volume of extraction solvent, volume of dispersive solvent, and salt concentration were optimized by means of experimental design. The statistical parameters of the derived model were R 2=0.9987 and F=17.83. The optimal conditions were 42.0μL for extraction solvent, 0.30mL for disperser solvent and 5% (w/v) for sodium chloride. The calibration linear range... 

A method based on solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) for determination of phenol in air was developed. Three different types of SPME fibers, polar and non-polar poly(dimethylsiloxane) (PDMS) and polyethylene glycol (PEG) were synthesized using sol-gel technology and their feasibility to the sampling of phenol were investigated. Different derivatization reagents for post on-fiber derivatization of phenol were studied. Important parameters influencing the extraction and derivatization process such as type of fiber coating, type and volume of derivatizing reagent, derivatization time and temperature,... 

A new type of composite material based on carbon nanotubes (CNTs) and sol-gel chemistry was prepared and used as sorbent for needle trap device (NTD). The synthesized composite was prepared in a way to disperse CNTs molecules in a sol-gel polymeric network. CNT/silica composites with different CNT doping levels were successfully prepared, and the extraction capability of each composite was evaluated. Effects of surfactant and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were also investigated. The applicability of the synthesized sorbent was examined by developing a method based on needle trap extraction (NTE) and gas chromatography mass spectrometry... 

Reinforced polydiphenylamine (PDPA) nanocomposite was synthesized by oxidation of diphenylamine in 4molL-1 sulfuric acid solution containing a fixed amount of carbon nanotubes (CNTs) in the presence of cetyltrimethylammonium bromide (CTAB). The surface characteristic of PDPA and PDPA/CNT nanocomposites was investigated using scanning electron microscopy (SEM). The prepared PDPA/CNT nanocomposite was used as an extraction medium for microextraction in packed syringe (MEPS) of selected pesticides from aquatic environment. The effect of CNT doping level and the presence of surfactant on the extraction capability of nanocomposite was investigated and it was revealed that when 4% (w/w) of CNT in...