Search for: chromatography
Total 297 records
Evaluation of polyaniline as a sorbent for SPE of a variety of polar pesticides from water followed by CD-MEKC-DAD, Article Chromatographia ; Volume 59, Issue 5-6 , 2004 , Pages 283-289 ; 00095893 (ISSN) ; Saraji, M ; Barceló, D ; Sharif University of Technology
A recently synthesized polyaniline (PANI) has been used and evaluated as a sorbent for solid-phase extraction of a variety of polar pesticides and some of their degradation products from water samples. Several classes of pesticides including phenoxy acids, triazines, ureas, oxime carbamates and carbamates were selected for this study. The determination of these pesticides was carried out using cycladextrin modified micellar electrokinetic chromatography equipped with diode array detection. The recovery results using PANI were compared with those obtained by C18, Isolute ENV+, Oasis HLB and LiChrolut EN. Effect of humic acid, as a major interference, on extraction recovery was also studied....
Determination of the pesticide naptalam and its degradation products by positive and negative ion mass spectrometry, Article Fresenius' Journal of Analytical Chemistry ; Volume 369, Issue 2 , 2001 , Pages 176-183 ; 09370633 (ISSN) ; Arshadi, M. R ; Asghari, F. S ; Sharif University of Technology
N-1-naphthylphtalamic acid (naptalam) and its degradation products, 1-naphthylamine and N-(1-naphthyl) phthalimide were simultaneously determined in river water by two independent mass spectrometric (MS) methods. These were negative ion MS (NIMS) and programmable temperature vaporizer gas chromatography mass spectrometry (PTV-GC MS) with electron impact ionization (positive ions). Prior to the NIMS analysis, the samples were preconcentrated by solid phase extraction (SPE) of C18 membrane discs. The PTV-GC MS studies were performed without any preconcentration procedure. Selected ion monitoring (SIM) and internal standardization with naphthalene were applied in both methods. The limits of...
Article Analytical Letters ; Volume 45, Issue 13 , 2012 , Pages 1777-1785 ; 00032719 (ISSN) ; Marzancola, M. G ; Es'haghi, A ; Sharif University of Technology
A polypropylene (PP) sheet was successfully applied as an extracting medium for trace enrichment of fluoxetine (FLX) from urine samples, followed by high performance liquid chromatography-fluorescence detection (HPLC-FD). The extraction medium was a square, 1 × 1 cm2 piece of polypropylene membrane sheet that was conditioned in methanol. The extraction process was conveniently carried out using a 5 mL urine sample. After extraction, the PP sheet was withdrawn and transferred to a glass vial for performing the desorption process using 210 μL organic solvent. After complete drying, the residue was dissolved in 50 μL of methanol and an aliquot of 20 μL was, finally, injected into the HPLC...
Multivariate analytical figures of merit as a metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry, Article Journal of Chromatography A ; Volume 1466 , 2016 , Pages 155-165 ; 00219673 (ISSN) ; Parastar, H ; Sharif University of Technology
The present contribution is devoted to develop multivariate analytical figures of merit (AFOMs) as a new metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC–MS). In this regard, new definition of sensitivity (SEN) is extended to GC × GC–MS data and then, other multivariate AFOMs including analytical SEN (γ), selectivity (SEL) and limit of detection (LOD) are calculated. Also, two frequently used second- and third-order calibration algorithms of multivariate curve resolution-alternating least squares (MCR-ALS) as representative of multi-set methods and parallel factor analysis (PARAFAC) as representative of...
On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography, Article Analytica Chimica Acta ; Volume 513, Issue 2 , 2004 , Pages 445-449 ; 00032670 (ISSN) ; Mohammadi, A ; Salemi, A ; Sharif University of Technology
A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer-acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of...
Development and Application of Multivariate Curve Resolution Techniques for the Analysis of Complex Chromatographic Data, Ph.D. Dissertation Sharif University of Technology ; Jalali Heravi, Mahdi
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...
Second-order calibration for the determination of fatty acids in pomegranate seeds by vortex-assisted extraction-dispersive liquid-liquid micro-extraction and gas chromatography-mass spectrometry, Article RSC Advances ; Volume 5, Issue 15 , 2015 , Pages 11633-11643 ; 20462069 (ISSN) ; Sereshti, H ; Parastar, H ; Sharif University of Technology
Multivariate curve resolution-alternating least squares (MCR-ALS) as a second-order calibration algorithm was proposed for the simultaneous analysis of eighteen fatty acid methyl esters (FAMEs) in a standard mixture and pomegranate seed sample using vortex-assisted extraction-dispersive liquid-liquid microextraction (VAE-DLLME), followed by gas chromatography-mass spectrometry (GC-MS). The chemometric resolution, identification and quantification of the target FAMEs in the standard mixture and real sample (i.e., the pomegranate seed) were carried out successfully in the presence of some uncalibrated interferences. The lack of fit (LOF) and reverse match factor (RMF) were used for the...
Electrospun superhydrophobic polystyrene hollow fiber as a probe for liquid–liquid microextraction with gas chromatography-mass spectrometry, Article Journal of Separation Science ; Volume 39, Issue 19 , 2016 , Pages 3782-3788 ; 16159306 (ISSN) ; Baktash, M. Y ; Jahandar, K ; Sharif University of Technology
Wiley-VCH Verlag 2016
A superhydrophobic polystyrene hollow fiber was electrospun around a copper spring collector. This approach led to the construction of a hollow fiber membrane, and the copper spring acted as a scaffold. The characteristic properties of the hollow fiber were studied by scanning electron microscopy. The membrane was used as a probe to transfer the extracting solvent from aquatic media to a gas chromatograph. After performing the liquid–liquid microextraction procedure on 10 mL of water sample by octanol, the whole solution was passed through the prepared polystyrene hollow fiber. Propanol, containing 2 mg/L lindane as the internal standard, was used for desorption and an aliquot of 2 μL of the...
Article Journal of Chromatography A ; Volume 1433 , February , 2016 , Pages 34–40 ; 00219673 (ISSN) ; Khanipour, P ; Roostaie, A ; Sharif University of Technology
In this study, a fast and sensitive flow injection μ-solid phase extraction (FI-μ-SPE) technique based on an electrospun polyaniline (PANI) nanocomposite in conjunction with gas chromatography-mass spectrometry (GC-MS) was developed. The PANI-based nanocomposite was synthesized by electrospinning of a solution containing polyvinyl alcohol (PVA)/PANI. The majority of PVA template was subsequently removed from the whole PVA/PANI nanofibers blend by exposing the electrospun nanocomposite to hot water. The homogeneity, porosity and characterization of the electrospun nanofibers were investigated by the scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Due to...
Novel unbreakable solid-phase microextraction fibers on stainless steel wire and application for the determination of oxadiargyl in environmental and agricultural samples in combination with gas chromatography-mass spectrometry, Article Talanta ; Vol. 128, issue , 2014 , Pages 231-236 ; ISSN: 00399140 ; Baghernejad, M ; Bagheri, H ; Sharif University of Technology
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...
Thorough analysis of Iranian spearmint essential oil: Combination of chemometrics and gas chromatography-mass spectrometry, Article Analytical Methods ; Vol. 6, Issue. 17 , 2014 , Pages 6753-6759 ; ISSN: 17599660 ; Moazeni-Pourasil, R. S ; Sereshti, H ; Sharif University of Technology
The components of Iranian spearmint essential oil were identified and quantified using gas chromatography-mass spectrometry (GC-MS) combined with chemometric tools. A multivariate curve resolution (MCR) approach was used to overcome the problems of background, baseline offset and overlapping/embedded peaks in GC-MS. The peaks were resolved using heuristic evolving latent projection (HELP) and multivariate curve resolution-alternating least squares (MCR-ALS) techniques. A new pure variable selection method named multivariate curve resolution-objective function equal to zero (MCR-FEQZ) is introduced and was applied in this work. The performance of this technique was evaluated and confirmed...
N-way partial least squares with variable importance in projection combined to GC×GC-TOFMS as a reliable tool for toxicity identification of fresh and weathered crude oils, Article Analytical and Bioanalytical Chemistry ; Volume 407, Issue 1 , January , 2015 , Pages 285-295 ; 16182642 (ISSN) ; Parastar, H ; Sharif University of Technology
Springer Verlag 2015
In this study, N-way partial least squares (NPLS) is proposed to correlate comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GCTOFMS) data of different aromatic oil fractions (fresh and weathered) to their toxicity values. Before NPLS modeling, since drift and wander of baseline interfere with information of sought analytes in GC×GC-TOFMS data, a novel method called two-dimensional asymmetric least squares is thus developed for comprehensive correction of the baseline contributions in both chromatographic dimensions. The algorithmis termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the...
Article International Journal of Engineering, Transactions B: Applications ; Volume 28, Issue 8 , 2015 , Pages 1115-1123 ; 1728-144X (ISSN) ; Alemzadeh, I ; Tabatabaee Yazdi, F ; Vossoughi, M ; Varidi, M ; Sharif University of Technology
Materials and Energy Research Center 2015
In this study, Lipase from Aspergillus Niger after extraction of medium culture was precipitated with different percentages of acetone and purified by ion exchange chromatography using SP-Sepharose HP and Q-Sepharose HP. The process of purification of the enzyme was studied by electrophoresis and the molecular weight was detected and determined by Zymography using overlying containing phenol red and Rhodamine B. The results showed that the vast majority of lipase from this strain has been precipitated by 70% saturation acetone, and leads to the 1.67 fold the purified enzyme, with special activities 32.8 U. mg-1 and efficiency of 38.5%. Using two-phase chromatography, enzyme specific activity...
Analysis of olive fruit essential oil: Application of gas chromatography-mass spectrometry combined with chemometrics, Article International Journal of Food Properties ; Volume 18, Issue 2 , Aug , 2015 , Pages 316-331 ; 10942912 (ISSN) ; Abbasi, A ; Parastar, H ; Moazeni, R. S ; Jalali Heravi, M ; Sharif University of Technology
Taylor and Francis Inc 2015
The extracted Iranian olive fruit essential oil was analyzed using gas chromatography-mass spectrometry. Multivariate curve resolution-alternative least squares approach was used to overcome the problem of background, baseline offset and overlapping/embedded peaks in gas chromatography-mass spectrometry. The analysis of gas chromatography-mass spectrometry data revealed that 90 components exist in the olive fruit essential oil. However, with the help of multivariate curve resolution-alternative least squares this number was extended to 141 components with concentrations higher than 0.01%. Major constituents in the olive fruit oil are 2-dodecenal (16.88%), 2-undecenal (10.71%), ethyl oleate...
Article International Journal of Engineering, Transactions B: Applications ; Volume 21, Issue 2 , 2008 , Pages 127-134 ; 1728-144X (ISSN) ; Alemzadeh, I ; Vossoughi, M ; Sharif University of Technology
Materials and Energy Research Center 2008
Fructose is utilized as a common sweetener in many food industries. Today, a large amount of HFCS (high fructose corn syrup, an equilibrium mixture of glucose and fructose) is produced by glucose isomerase, immobilized enzymes from corn starch. There are a lot of date palms in Iran. Date is a favorable source of carbohydrates, and a suitable source for HFDS (high fructose date syrup) production. In this investigation, date syrup properties were first determined and the operational conditions for glucose isomerase application were optimized respectively. Ion exchange chromatography has been utilized for carbohydrate separation. Fructose obtained from chromatographic column reached 90 %...
Characterization of essential oil components of Iranian geranium oil using gas chromatography-mass spectrometry combined with chemometric resolution techniques, Article Journal of Chromatography A ; Volume 1114, Issue 1 , 2006 , Pages 154-163 ; 00219673 (ISSN) ; Zekavat, B ; Sereshti, H ; Sharif University of Technology
The essential oil components of geranium oil cultivated in center of Iran were identified and determined using gas chromatography-mass spectrometry data combined with the chemometric resolution techniques. A total of 61 components accounting for 91.51% were identified using similarity searches between the mass spectra and MS database. This number was extended to 85 components using chemometric techniques. Various chemometric methods such as morphological scores, simplified Borgen method (SBM) and fixed size moving window evolving factor analysis (FSMWEFA) were used for determining the number of components, pure variables, zero concentration and selective regions. Then the overlapping peak...
Article Journal of AOAC International ; Vol. 97, issue. 1 , 2014 , p. 12-18 ; Leardi, R ; Jalali-Heravi, M ; Sharif University of Technology
This paper reviews the applications of experimental design to optimize some analytical chemistry techniques such as extraction, chromatography separation, capillary electrophoresis, spectroscopy, and electroanalytical methods
N-way partial least squares with variable importance in projection combined to GC × GC-TOFMS as a reliable tool for toxicity identification of fresh and weathered crude oils, Article Analytical and Bioanalytical Chemistry ; Volume 407, Issue 1 , 2014 , pp 285-295 ; ISSN: 16182650 ; Parastar, H ; Sharif University of Technology
In this study, N-way partial least squares (NPLS) is proposed to correlate comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS) data of different aromatic oil fractions (fresh and weathered) to their toxicity values. Before NPLS modeling, since drift and wander of baseline interfere with information of sought analytes in GC × GC-TOFMS data, a novel method called two-dimensional asymmetric least squares is thus developed for comprehensive correction of the baseline contributions in both chromatographic dimensions. The algorithm is termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the...
Chemometrics-assisted gas chromatographic-mass spectrometric analysis of volatile components of olive leaf oil, Article Journal of the Iranian Chemical Society ; Volume 10, Issue 1 , 2013 , Pages 169-179 ; 1735207X (ISSN) ; Abbasi, A ; Moazeni, R. S ; Parastar, H ; Jalali Heravi, M ; Sharif University of Technology
Iranian olive leaf essential oil components were extracted by microwave-assisted hydrodistillation and analyzed using gas chromatography-mass spectrometry. Ninety-seven components were identified by direct similarity searches for olive leaf essential oil. Chemometrics was used to find more components with the help of multivariate curve resolution methods. Eigenvalues-based methods and Malinowski functions were used for chemical rank determination of GC-MS data. Multivariate curve resolution-alternative least squares as an iterative method was used for resolving the overlapped and embedded peaks. With the use of this method the number of 97 components was extended to 127 components. Major...
Chemically bonded carbon nanotubes on modified gold substrate as novel unbreakable solid phase microextraction fiber, Article Microchimica Acta ; Volume 174, Issue 3 , September , 2011 , Pages 295-301 ; 00263672 (ISSN) ; Ayazi, Z ; Sistani, H ; Sharif University of Technology
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...