Biomedical subjects

Mojtaba Shamsipur

Publications and source records attributed to Mojtaba Shamsipur.

At least 19 recordsLinked to original sources

PubMed2006

19F NMR as a powerful technique for the assay of anti-psychotic drug haloperidol in human serum and pharmaceutical formulations.

19F nuclear magnetic resonance was used as a suitable analytical tool for the identification and selective determination of haloperidol in human serum and pharmaceutical preparations. The method is based on the integration of appropriate signals of haloperidol and trifluoroacetic acid as an internal standard. The proposed method is a rapid and facile, while without any sample pretreatment, manipulation of large samples and lengthy instrument time. The regression equation for haloperidol in human serum showed a good linearity in the range of 60-600 microg ml(-1) with a detection limit of 1.4 microg ml(-1). The mean recovery results on human serum samples ranged from about 96-103%, with relative standard deviations <8%. The method was also applied successfully to the determination of haloperidol in real pharmaceutical samples, and compared with the results obtained by a reference method. The drug's degradation was studied by the proposed method in hydrochloric acid media and main products were identified.

Antipsychotic Agents↗

PubMed2006

Nano-structured lead dioxide as a novel stationary phase for solid-phase microextraction.

The first study on the high efficiency of nano-structured lead dioxide as a new fiber for solid-phase microextraction (SPME) purposes has been reported. The size of the PbO2 particles was in the range of 34-136 nm. Lead dioxide-based fibers were prepared via electrochemical deposition on a platinum wire. The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using headspace solid-phase microextraction (HS-SPME) mode coupled to gas chromatography-flame ionization detection (GC-FID). The results obtained proved the suitability of proposed fibers for the sampling of organic compounds from water. The extraction procedure was optimized by selecting the appropriate extraction parameters, including preparation conditions of coating, salt concentration, time and temperature of adsorption and desorption and stirring rate. The calibration graphs were linear in a concentration range of 0.1-100 microg l(-1) (R2 > 0.994) with detection limits below 0.012 microg l(-1) level. Single fiber repeatability and fiber-to-fiber reproducibility were less than 10.0 and 12.5%, respectively. The PbO2 coating was proved to be very stable at relatively high temperatures (up to 300 degrees C) with a high extraction capacity and long lifespan (more than 50 times). Higher chemical resistance and lower cost are among the advantages of PbO2 fibers over commercially available SPME fibers. Good recoveries (81-108%) were obtained when environmental samples were analyzed.

Adsorption↗

PubMed2006

A study of peroxyoxalate-chemiluminescence of 4,4'-bis{[4,6-bis (2-hydroxyethyl)amino-1,3,5-triazin-2-yl]amino}stilbene-2,2'-disulfonic acid-disodium salt as a novel blue fluorescer.

The chemiluminescence arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of brightener 4,4'-bis{[4,6-bis(2-hydroxyethyl)amino-1,3,5-triazin-2-yl]amino}stilbene-2,2'-disulfonic acid-disodium salt (Triazinyl) has been studied. The influence of concentration of TCPO, hydrogen peroxide, Triazinyl, base catalysts and temperature on the resulting chemiluminescence was investigated. The kinetic parameters for the peroxyoxalate-chemiluminescence (PO-CL) of Triazinyl were evaluated from computer fitting of the resulting intensity-time plots. The activation energies, E(a), were evaluated from temperature dependence of the corresponding rise and fall rate constants.

Fluorescence↗

PubMed2006

Electrochemical oxidation of 2,3-dimethylhydroquinone in the presence of 1,3-dicarbonyl compounds.

The electrooxidation of 2,3-dimethylhydroquinone (1) has been studied in the presence of 2-phenyl-1,3-indandione (3a), 3-hydroxy-1H-phenalen-1-one (3b), and 2-chloro-5,5-dimethyl-1,3-cyclohexanedione (3c) as CH acid nucleophiles in water/acetonitrile (85/15) solution, using cyclic voltammetry and controlled-potential coulometry. The results indicate that p-benzoquinone, generated by electrochemically driven oxidation of the 2,3-dimethylhydroquinone (1), is scavenged by 3a-c, to give related products (5a, 9b, 8c) via various electrochemical mechanisms. The electrochemical syntheses of 5a, 9b, and 8c have been successfully performed in one-pot in an undivided cell using an environmentally friendly method with high atomic economy.

Benzofurans↗

PubMed2006

Copper(II)-selective fluorimetric bulk optode membrane based on a 1-hydroxy-9,10-anthraquinone derivative having two propenyl arms as a neutral fluorogenic ionophore.

A new optical chemical sensor has been developed for the selective determination of copper(II) ions in aqueous solutions. The reversible sensing system was prepared by incorporating 1-hydroxy-2-(prop-2'-enyl)-4-(prop-2'-enyloxy)-9,10-anthraquinone (AQ) as a neutral Cu2+-selective fluoroionophore in the plasticized PVC membrane with potassium tetrakis(p-chlorophenyl borate) as an anionic additive. The response of the sensor is based on the fluorescence quenching of AQ by Cu2+ ions. At a pH 5.5, the proposed sensor displays a calibration response for Cu2+ over a wide concentration range of 1.0 x 10(-2) to 1.0 x 10(-6) M, with a relatively fast response of less than 40 s. In addition to high stability and reproducibility, the sensor shows a unique selectivity towards Cu2+ ion with respect to common co-existing cations. The proposed fluorescence optode was applied successfully to the determination of copper(II) in black tea samples.

Anthraquinones↗

PubMed2006

An improved electrochemical method for the synthesis of some benzofuran derivatives.

Electrochemical oxidation of catechol and some 3-substituted catechols (1a--c) has been studied in the presence of 2-chloro-5,5-dimethyl-1,3-cyclohexanedione (3) in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a--c) participate in a Michael addition reaction with 2-chloro-5,5-dimethyl-1,3-cyclohexanedione (3) with consumption of only two electrons per molecule of (1a--c) to from the corresponding benzoforans (10a--c). The electrochemical synthesis of benzofurans has been successfully performed at a carbon rod electrode and in an undivided cell with high yields and purity.

Benzofurans↗

PubMed2005

Spectroscopic and conductometric studies of molecular complex formation between 2,4,6-trinitrophenol and diaza-18-crown-6, tetraaza-14-crown-4 and cryptand C222 in 1,2-dichloroethane solution.

The formation of molecular complexes between 2,4,6-trinitrophenol (TNP) and aza-substituted macrocycles diaza-18-crown-6 (DA18C6), tetraaza-14-crown-4 (TA14C4) and cryptand C222 in 1,2-dichloroethane solution was investigated spectrophotometrically and conductometrically. The mole ratio and continuous variations studies based on both physicochemical techniques employed clearly revealed the formation of both 1:1 and 2:1 (TNP:macrocycle) adducts in solution. Formation of the resulting complexes was also confirmed by 1H NMR and IR spectroscopic studies. Formation constants of the resulting complexes were evaluated from computer fitting of the corresponding mole ratio data. Stability of the resulting complexes was found to vary in the order C222 approximately TA14C4 > DA18C6.

Crown Ethers↗

PubMed2005

Copper(II)-selective fluorimetric bulk optode membrane based on a 1-hydroxy-9,10-anthraquinone derivative having two propenyl arms as a neutral fluorogenic ionophore.

A new optical chemical sensor has been developed for the selective determination of copper(II) ions in aqueous solutions. The reversible sensing system was prepared by incorporating 1-hydrpxy-2-(prop-2'-enyl)-4-(prop-2'-enyloxy)-9,10-anthraquinone (AQ) as a neutral Cu2+-selective fluoroionophore in the plasticized PVC membrane with potassium tetrakis(p-chlorophenyl borate) as an anionic additive. The response of the sensor is based on the fluorescence quenching of AQ by Cu2+ ions. At a pH 5.5, the proposed sensor displays a calibration response for Cu2+ over a wide concentration rang of 1.0 x 10(-2) to 1.0 x 10(-6) M, with a relatively fast response of less than 40 s. In addition to high stability and reproducibility, the sensor shows a unique selectivity towards Cu2+ ion with respect to common co-existing cations. The proposed fluorescence optode was applied successfully to the determination of copper(II) in black tea samples.

Anthraquinones↗

PubMed2005

Development of a PVC-membrane ion-selective bulk optode, for UO2(2+) ion, based on tri-n-octylphosphine oxide and dibenzoylmethane.

A novel uranyl ion-selective bulk optode membrane, incorporating tri-n-octylphosphine oxide for cation recognition and a lipophilic chromoionophore dibenzoylmethane, has been prepared. The PVC membrane composition was optimized to result in the widest working concentration range. The response range of the proposed optode is 4.1 x 10(-6) to 2.0 x 10(-4) mol L(-1) UO2(2+). The probe works at pH 4.0. Ion interference is low and selectivity, reproducibility, and stability are good.

Journal Article↗

PubMed2005

1H NMR studies of homo and mixed ligand complexes of Tl+ ion with several polyazamacrocycles.

Proton NMR was used as a probe to study the interaction of the Tl(+) ion with 9-18-membered macromonocyclic tri-, tetra-, and hexaamines in dimethylformamide (DMF) solution. A study of proton chemical shift of ligands as a function of Tl(+) ion to ligand mole ratio revealed that the complexation reactions occur in a stepwise manner. Formation of a 1:1 complex is followed by the addition of a second complexant molecule to form a homo-sandwich complex for triazamacrocycle ligands and a mixed ligand complex in the case of hexamethylhexacyclen (HMHCY) and 1,4,7-triazacyclononane ([9]aneN(3)). The formation constants of resulting 1:1 and 1:2 (homo and mixed ligand sandwich) complexes in DMF solution were evaluated from computer fitting of the chemical shift-mole ratio data. The mixed ligand complexes may be more stable than the parent complex in which both ligands are the same. The influence of cavity size and substitution of methyl groups on nitrogen atoms of the macrocyclic ring the stability of the resulting complexes is discussed. The geometries of the tri- and tetraazamacrocycle ligands and their Tl(+) ion complexes were optimized by an ab initio method, and the calculated binding energies of resulting complexes were compared. Both the experimental and theoretical studies revealed that, in the presence of methyl groups, the stability of triazamacrocycle complexes with Tl(+) ion was decreased.

Dimethylformamide↗

PubMed2005

Solid phase extraction and determination of sub-ppb levels of hazardous Hg2+ ions.

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions from aqueous samples for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CV-AAS). The Hg(2+) ions were adsorbed selectively and quantitatively during the passage of aqueous samples through octadecyl silica membrane disks modified by isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE). The retained Hg(2+) ions were then stripped from the disk with minimal amounts of 0.5 M hydrobromic acid (two 8 ml portions) as eluent, and determined by CV-AAS. The break-through volume of the method is greater than 3000 ml, which results in enrichment factors >150. Maximum capacity of the membrane disks modified with 10mg of the ligand was found to be 350+/-30 microg of mercury(II), and the limit of detection is 0.005 ng ml(-1). The effect of various cationic interferences on the recovery of mercury in binary mixtures was studied. The method was applied to the recovery of Hg(2+) ions from different synthetic and tap water samples, as well as the determination of mercury in human hair samples.

Environmental Monitoring↗

PubMed2005

Preparation of a diclofenac potentiometric sensor and its application to pharmaceutical analysis and to drug recovery from biological fluids.

A novel diclofenac ion-selective electrode is prepared, characterized and used in pharmaceutical analysis. The diclofenac complex with hexadecylpyridinium bromide is obtained in situ by soaking the PVC-membranes in a 1x10(-2) M diclofenac solution. Among four different solvent mediators tested, dibutyl phthalate (DBP) exhibited a proper behavior including Nernstian slope of the calibration curve, fast response time and good reproducibility of the emf values. The electrode exhibits a Nernstian slope of -59+/-1 mV decade(-1) for diclofenac in the concentration range 1.0x10(-5) to 1.0x10(-2) M with a limit of detection of 4.0x10(-6) M. The electrode displays a good selectivity for diclofenac with respect to a number of common inorganic and organic species. It can be used in a pH range of 6.0-9.0. The membrane sensor was successfully applied to the determination of diclofenac in its tablets as well as for its recovery from blood serum and urine samples.

Biosensing Techniques↗

PubMed2005

PVC membrane potentiometric sensor based on 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthroline-phane for selective determination of neodymium(III).

Spectrofluorometric studies on the binding properties of 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthrolinephane (L) toward La3+, Sm3+, Gd3+, Yb3+, and Nd3+ in methanol solution revealed the occurrence of both 1:1 and 2:1 (ligand/metal) complexation with a stability order of Nd3+ > Yb3+ > Gd3+ > Sm3+ > La3+. Consequently, L was used as a suitable neutral ionophore for the preparation of a novel polymeric membrane-selective electrode for Nd3+ ion. The electrode exhibited a Nernstian response over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-2) M) with a low limit of detection of 7.9 x 10(-7) M. The electrode possesses a fast response time of <5 s and can be used for at least 9 weeks without observing any considerable deviation. The proposed electrode revealed a very good selectivity for Nd3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, including members of the lanthanide family other than Nd3+. The potentiometric response of the electrode is independent of the pH of test solution in the pH range 4.0-6.5. The proposed electrode was successfully applied to the recovery of Nd3+ ion from tap water samples and, also, as an indicator electrode, in potentiometric titration of neodymium(III) ions.

Journal Article↗

PubMed2005

Spectrophotometric study of interaction of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with diaza-18-crown-6 and diaza-15-crown-5 in acetonitrile and chloroform solutions.

Interactions of diaza-18-crown-6 and diaza-15-crown-5, as electron donors, with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), as an electron acceptor, have been investigated spectrophotometrically in acetonitrile and chloroform solutions. The results indicated immediate formation of an electron donor-electron acceptor complex DA: [reaction in text] which is followed by two relatively slow consecutive reactions: [reaction in text]. The pseudo-first-order rate constants for the formation of the ionic intermediate and the final product have been evaluated at various temperatures by computer fitting of the absorbance time data to appropriate equations. The formation constants of the resulting DA complexes have also been determined. The influences of both the azacrown's structure and the solvent properties on the formation of DA complexes and the rates of subsequent reactions are discussed.

Acetonitriles↗

PubMed2005

A study of quenching effect of sulfur-containing amino acids L-cysteine and L-methionine on peroxyoxalate chemiluminescence of 7-amino-4-trifluoromethylcumarin.

The quenching effect of L-cysteine and L-methionine on strong chemiluminescence of bis-(2,4,6-trichlorophenyl)oxalate-H(2)O(2) system in the presence of 7-amino-4-trifluoromethylcumarin was studied. The chemiluminescence parameters were evaluated from computer fitting of the resulting intensity-time plots. Both systems resulted in Stern-Volmer plots in the quencher concentration range of 6.5 x 10(-5) to 5.2 x 10(-4)M with k(Q) values of 1.15 x 10(4) and 1.28 x 10(4)M(-1) for L-cysteine and L-methionine, respectively.

Coumarins↗

PubMed2005

Spectrofluorometric study of complexation of some amino derivatives of 9,10-anthraquinone with beta-cyclodextrin.

Complexation reactions between 1-amino-9,10-anthraquinone (AA1), 1-amino-2-methyl-9,10-anthraquinone (AA2), 1-amino-2,4-dimethyl-9,10-anthraquinone (AA3) and 1-amino-2-ethyl-9,10-anthraquinone (AA4) and beta-cyclodextrin were studied spectrofluorometrically, under optimized experimental conditions. The formation constants of the resulting 1:1 beta-cyclodextrin complexes were evaluated and found to decrease in the order AA4>AA1>AA3>AA2. Possible reasons for the observed stability sequence are discussed based on the structures proposed for the resulting inclusion complexes.

Amines↗

PubMed2005

Flotation-separation and ICP-AES determination of ultra trace amounts of copper, cadmium, nickel and cobalt using 2-aminocyclopentene-1-dithiocarboxylic acid.

A rapid flotation method for separation and enrichment of ultra trace amounts of copper(II), cadmium(II), nickel(II) and cobalt(II) ions from water samples is established. At pH 6.5 and with sodium dodecylsulfate used as a foaming reagent, Cu2+, Cd2+, Ni2+ and Co2+ were separated simultaneously with 2-aminocyclopentene-1-dithiocarboxylic acid (ACDA) added to 1 l of aqueous solution. The proposed procedure of preconcentration is applied prior to the determination of these four analytes using inductivity coupled plasma-atomic emission spectrometry (ICP-AES). The effects of pH, concentration of ACDA, applicability of different surfactants and foreign ions on the separation efficiency were investigated. The preconcentration factor of the method is 1000 and the detection limits of copper(II), cadmium(II), nickel(II) and cobalt(II) ions are 0.078, 0.075, 0.072 and 0.080 ng ml(-1), respectively.

Cadmium↗

PubMed2005

Preparation of a novel iodide-selective electrode based on iodide-miconazole ion-pair and its application to pharmaceutical analysis.

An iodide-miconazole ion-paired complex was used as a suitable ion-exchanger for the preparation of a plasticized-PVC membrane electrode. Among different solvent mediators tested, dioctylsebacate exhibited the proper response characteristics, including Nernstian slope of the calibration curve, fast response time and good reproducibility of the emf values. The electrode exhibits a Nernstian slope of -59.8 +/- 0.5 mV decade(-1) for I- ion over a concentration range of 1.0 x 10(-5) - 1.0 x 10(-2) M with a limit of detection of 7.0 x 10(-6) M. The electrode displays a good selectivity for I- with respect to a number of inorganic and organic species. It canbe used over a pH range of 2.5 - 8.5. The membrane sensor was successfully applied to the determination of iodide in water samples and blood serum, as well as in pharmaceutical products such as iodoquinol and thyroxin.

Antifungal Agents↗