Ali Reza Ghiasvand

Amino ethyl-functionalized nanoporous silica as a novel fiber coating for solid-phase microextraction

Nanoporous silica (SBA-15) was prepared and functionalized with 3-[Bis(2-hydroxyethyl)amino] propyl-triethoxysilane (HPTES) to be used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared HPTES-SBA-15 particles had a lengthy morphology and a specific surface area of 790 m(2) g(-1). They were characterized by N(2) sorption analyses, scanning electron microscopy and thermogravimetric analysis. The prepared nanomaterial was immobilized onto a copper wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of BTEX and some phenolic compounds in combination with GC-MS. For optimization of factors affecting the extraction efficiency of the phenolic compounds, a simplex optimization method was used. The proposed fiber showed some selectivity towards the polar phenolic compounds with extraction efficiencies better than a PDMS commercial fiber. The repeatability for one fiber (n=5), expressed as relative standard deviation (RSD), was between 6.5% and 9.8% and the reproducibility for five prepared fibers was between 8.2% and 11.3% for the test compounds. No significant change was observed in the extraction efficiency of the new SPME fiber over 50 extractions. The fiber was successfully applied to the determination of phenolic compounds in spiked river water and sewage samples. Thus, HPTES-SBA-15 fiber is a promising alternative to the commercial fibers as it is robust, selective, highly porous and easily and inexpensively prepared.

Development of a simple device for dispersive liquid-liquid microextraction with lighter than water organic solvents: Isolation and enrichment of glycyrrhizic acid from licorice

A simple device was developed that makes the use of lighter than water organic solvents feasible in dispersive liquid-liquid microextraction (DLLME) method. In the ordinary DLLME, the fact that a heavier than water organic solvent must be used, to be sedimented at the conical bottom of a centrifuge tube, limits the applications of this method in some extent. In the developed method, a glass tube with a narrow neck is inserted inside the centrifuge tube. After phase separation, the organic solvent is accumulated in the narrow neck of the device and therefore, can be simply collected by a micro-syringe. The DLLME method with the proposed device was tested for the enrichment of glycyrrhizic acid from aqueous extracts of licorice before analysis by a HPLC method. n-Hexanol and acetone were used as the organic and disperser phases, respectively. Effects of pH, salt concentration and phase volumes on the extraction of the analyte were optimized using a central composite (response surface) design. Under the optimized conditions (i.e. pH 1.3, ionic strength 0.2 mol L(-1), n-hexanol 140 microL and acetone 0.8 mL) an extraction recovery of 104.1 (+/-5.1)% and an enrichment factor of 54 were obtained. The proposed method was successfully applied for the study of glycyrrhizic acids level of licorice roots grown in three regions of Lorestan province, Iran, with different climate conditions.

Homogeneous liquid-liquid extraction method for the selective separation and preconcentration of ultra trace molybdenum

A new simple and efficient homogeneous liquid-liquid extraction method for the selective separation and preconcentration of molybdenyl ions was developed. alpha-Benzoin oxime (ABO) was investigated as a complexing ligand, and perfluorooctanoate ion (PFOA(-)) was applied as a phase-separator agent under strongly acidic conditions. Under the optimal conditions ([ABO]=2.1x10(-3)M, [PFOA(-)]=1.8x10(-2)M, [HNO(3)]=1.7M, [acetone]=11.8% (v/v)), 10mug of molybdenum in 5ml aqueous phase could be extracted quantitatively into 40mul of the sedimented phase. The maximum concentration factor was 125-fold. Thiocyanate was applied as a chromogenic reagent for the direct spectrophotometric determination of molybdenum in the sedimented phase. The reproducibility of the proposed method is at the most 2.4%. The influence of the type and concentration of acid solution, the concentration of ABO, the type and volume of the water-miscible organic solvent, the concentration of PFOA(-), and the effect of different diverse ions on the extraction and determination of molybdenum(VI) were investigated. The proposed method was applied to the extraction and determination of molybdenum(VI) in natural water, Spinach, and Lucerne samples. A satisfactory agreement exists between the results obtained by the proposed method and those reported by GF-AAS.

Selective preconcentration of ultra trace copper(II) using octadecyl silica membrane disks modified by a recently synthesized glyoxime derivative

A new simple and reliable method has been developed to selectively separate and concentrate ultra trace amounts of copper ion in aqueous samples for subsequent measurement by atomic absorption spectrometry (AAS). The Cu(2+) ions are adsorbed selectively and quantitatively during passage of aqueous solutions through octadecyl silica membrane disks modified with bis(2-hydroxyphenylamino) glyoxime. The retained copper ions then stripped from the disk with a minimal amount of 0.2M nitric acid solution as eluent, and determined by AAS. The proposed method permitted large enrichment factors of about 100 or higher. The limit of detection of the proposed method is 0.004ngml(-1). The maximum capacity of the membrane disks modified with 25mg of ligand was found to be 280+/-32mug of copper(II). The effects of various cationic interferences on the percent recovery of copper in binary mixtures were studied. The method was successfully applied to the recovery and determination of copper in several water samples.

Reversed-phase dispersive liquid–liquid microextraction with central composite design optimization for preconcentration and HPLC determination of oleuropein

A reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) method was developed for the preconcentration and direct HPLC determination of oleuropein in olives processing wastewater (OPW) and olive leaves extracts. In conventional DLLME, the sedimented phase is a micro-drop of a chlorinated organic solvent that is not compatible with RP-HPLC. Therefore, solvent evaporation and reconstitution with an appropriate solvent is often required. In RP-DLLME, this problem was overcome by overturning the solvent polarity in the ordinary DLLME and replacing the organic solvent with water. A central composite chemometrics design was used for multivariate optimization of the effects of five different parameters influencing the extraction efficiency of the method. In the optimized conditions, a mixture of 1.4 mL of an ethyl acetate extract of sample and 40 microL water (pH 5.0) was rapidly injected into 5.3 mL of cyclohexane. After centrifugation of the formed cloudy mixture, a micro-drop of the aqueous phase was sedimented at the conical bottom of the centrifuge tube. This phase, that contained the preconcentrated and partially purified analyte, was directly injected into an RP-HPLC column for analysis. A mean extraction recovery of 102.5 (+/-4.5) % with enrichment factors exceeding 38, was obtained for five replicated analysis. The detection limit of the method (3 sigma) for OE was 0.02 microg L(-1) for OPW and 2 x 10(-3) mg kg(-1) for olive leaves samples. The results showed that, RP-DLLME is a promising technique which is quick, easily operated and can be directly coupled to HPLC.

Extraction of uranium from solid matrices using modified supercritical fluid CO2

Abstract The equilibrium solubility of uranyl nitrate in supercritical fluid carbon dioxide (SF-CO 2 ) in the absence and presence of different modifiers was investigated. In the presence of methanol and HNO 3 , uranyl nitrate showed a considerable solubility in SF-CO 2 . SF-CO 2 modified with different co-extractants such as tributylphosphate (TBP), methylisobutyl ketone (MIBK), acetylacetone (AA) and methanol (MeOH) at 60°C and 250 atm was used for the extraction of uranyl nitrate from cellulose-based filter papers. The extraction efficiency of the system for uranyl ion was found to decrease in the order TBP>MIBK>AA>MeOH. The use of eight potential chelating agents bis (2-ethylhexyl)hydrogen phosphate (HDEPH), tri- n -octylphosphine oxide (TOPO), dicyclohexyl-18-crown-6 (DC18C6), dibenzoylmethane (DBM), 8-hydroxyquinoline (HOX), diphenylaminesulfonic acid (DPASA) 1,4- bis -[4-methyl-5-phenyl-2-oxazolyl]benzene (DMPOPOP) and TBP for uranyl ion extraction from filter paper samples by methanol modified SF-CO 2 was investigated. The organophosphorous reagents TOPO and HDEPH showed the highest extraction efficiency in the series. The synergistic extraction of uranyl nitrate with HDEPH and TOPO in the presence of DC18C6 was also studied.

CMK-3 nanoporous carbon as a new fiber coating for solid-phase microextraction coupled to gas chromatography-mass spectrometry.

CMK-3 nanoporous carbon was prepared and characterized as a highly porous fiber coating, with a highly ordered carbon framework, for solid-phase microextraction (SPME). The nanomaterial was immobilized onto platinum, stainless steel and copper metal wires for preparation of new SPME fibers. The copper-CMK-3 fiber showed superior properties and therefore was applied for extraction of some phenolic compounds in combination with GC-MS. For optimization of the extraction conditions, a simplex optimization method was used. The selected conditions were: sample volume 13 ml, extraction temperature 56°C, extraction time 7 min, ultrasonic time 5.5 min, pH 5 and salt concentration 8.9%. The selected fiber showed some selectivity towards the polar phenolic compounds and its extraction efficiency was better than a commercial PDMS fiber. Linear calibration curves with correlation coefficients better than 0.99 and detection limits in the range from 0.002 to 0.068 μg mL(-1) were obtained for the fiber. No significant change was observed in the extraction efficiency of the new SPME fiber over at least 40 extractions. The fiber was successfully used for the determination of phenolic compounds in natural water samples.

A needle trap device packed with a sol-gel derived, multi-walled carbon nanotubes/silica composite for sampling and analysis of volatile organohalogen compounds in air.

A needle trap device (NTD) packed with silica composite of multi-walled carbon nanotubes (MWCNTs) prepared based on sol-gel technique was utilized for sampling and analysis of volatile organohalogen compounds (HVOCs) in air. The performance of the NTD packed with MWCNTs/silica composite as sorbent was examined in a variety of sampling conditions and was compared with NTDs packed with PDMS as well as SPME with Carboxen/PDMS-coated fibers. The limit of detection of NTDs for the GC/MS detection system was 0.01-0.05 ng mL(-1) and the limit of quantitation was 0.04-0.18 ng mL(-1). The RSD were 1.1-7.8% for intra-NTD comparison intended for repeatability of technique. The NTD-MWCNTs/silica composite showed better analytical performances compared to the NTD-PDMS composite and had the same analytical performances when compared to the SPME-Carboxen/PDMS fibers. The results show that NTD-MWCNTs-GC/MS is a powerful technique for active sampling of occupational/environmental pollutants in air.

A novel needle trap device with single wall carbon nanotubes sol-gel sorbent packed for sampling and analysis of volatile organohalogen compounds in air.

This paper describes a new approach that combines needle trap devices (NTDs) with a newly synthesized silanated nano material as sorbent for sampling and analysis of HVOCs in air. The sol-gel technique was used for preparation of the single wall carbon nanotube (SWCNT)/silica composite as sorbent, packed inside a 21-gauge NTD. Application of this method as an exhaustive sampler device was investigated under different laboratory conditions in this study. Predetermined concentrations of each analyte were prepared in a home-made standard chamber, and the effects of experimental parameters, such as temperature, humidity, sampling air flow rate, breakthrough volume and storage time on NTD, and the sorbent performance were investigated. The proposed NTD was used in two different modes and two different injection methods, and an NTD with a side hole, a narrow neck glass liner and syringe pump assisted injection of carrier gas were applied. The NTD packed with SWCNTs/silica composite was compared to the NTD packed with PDMS and also SPME with CAR/PDMS. For four compounds, LOD was 0.001-0.01 ng mL(-1), LOQ was 0.007-0.03 ng mL(-1), and the relative standard division for repeatability of method was 2.5-6.7%. The results show that the incorporation of NTD and SWCNTs/silica composite is a reliable and effective approach for the sampling and analysis of HVOCs in air. Coupling this system to GC-MS make it more sensitive and powerful technique.

A solid-phase microextraction platinized stainless steel fiber coated with a multiwalled carbon nanotube-polyaniline nanocomposite film for the extraction of thymol and carvacrol in medicinal plants and honey.

A mechanically hard and cohesive porous fiber, with large surface area, for more strong attachment of the coating was provided by platinizing a stainless steel wire. Then, the platinized stainless steel fiber was coated with a multiwalled carbon nanotube/polyaniline (MWCNT/PANI) nanocomposite using electrophoretic deposition (EPD) method and applied for the extraction of thymol and carvacrol with direct-immersion solid-phase microextraction (DI-SPME) method followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) quantification. To provide a larger coarse surface for the tightened attachment of coating on the fiber, a stainless steel wire was platinized using a suitable optimized EPD method. Different experimental parameters were studied and the optimal conditions were obtained as: pH of the sample solution: 2; extraction time: 60min; salt content in the sample solution: 1% w/v NaNO3; desorption time: 60min; type and volume of the desorption solvent: acetonitrile, 100μL. Under the optimized conditions, limits of detection (LODs) were 0.6 and 0.8μgmL(-1) for thymol and carvacrol, respectively. Linear dynamic range (LDR) for the calibration curves of both analytes were 1-80μgmL(-1). Relative standard deviation (RSD%, n=6) was 6.8 for thymol and 12.7 for carvacrol. The proposed fiber was successfully applied for the recovery and determination of thymol and carvacrol in thyme, savory, and honey samples.