UV-visible spectroscopic and electrochemical methods were used to study the interaction of some fluoroquinolones with calf-thymus DNA. UV-visible spectroscopy was used to evaluate the binding constants of drug-DNA complexes and to elucidate the nature of binding of of these drugs with DNA. The interaction of the studied fluoroquinolones with DNA was investigated by cyclic voltammetry at a glassy carbon electrode with an irreversible electrochemical equation. The diffusion coefficients of both free and bound fluoroquinolones (Df, Db), the binding constant (K), and the binding site size (s) of fluoroquinolone-DNA complexes were obtained simultaneously by non-linear fit analysis of the experimental data. The results suggested that fluoroquinolones bind to DNA through an electrostatic mode of interaction with partial intercalation. DNA-modified glassy carbon electrodes were used for the first time as a biosensor for the determination of the studied compounds. Differential-pulse anodic stripping voltammetry was used for investigating different factors that affect the oxidation of the studied fluoroquinolones at the DNA-biosensor. A method was proposed for the determination of ciprofloxacin concentration both in tablets and in a biological fluid (urine). The method was found to be sensitive, accurate, and inexpensive. Kinetics of osmium tetroxide catalyzed-oxidation of the studied fluoroquinolones by potassium hexacyanoferrate (III) in alkaline medium were studied. The rate was found to be independent on the concentration of hexacyanoferrate (III), and first order with respect to both fluroquinolone and OsO4. An empirical rate law was derived for the reaction, and the effect of various variables on the rate of reaction was studied. Thermodynamic parameters (Ea, ?H*, ?S*, ?G*) were also calculated.
Monday, January 18, 2010
Kinetic Studies of the Hydrolysis of Furfurylidenefuroyl Hydrazone Derivatives, Solvatochromism and Fluorimetric Determination of Iron (III)
Preferential solvation of di-2-pyridylketonebenzoyl hydrazone was investigated in aqueous-ethanol binary mixtures . The kinetics and mechanism of the hydrolysis of a series of substituted furfurylidenefuroyl hydrazones (X-FFH) in 25% (v/v) ethanol-buffer mixtures have been studied by ultraviolet visible spectrophotometry at different temperatures in the range 22-500C. The hydrolysis reactions were found to follow first-order kinetics. The effect of pH, molecular structure and temperature on the rate of hydrolysis have been discussed. A mechanism for the hydrolysis is postulated in which the attack of water on the protonated substrate is subject to general acid-base catalysis using HCl-sodium acetate buffer solution. The hydrolysis of 5-Chlorothiophenylidene salicoyl hydrazone (CTSH) was found to obey specific acid catalysis using HCl-KCl buffer solutions. The observed rate constants and the catalytic rate constants with respect to H+, HC2O4- and H2C2O4 were calculated. Activation energy and thermodynamic parametres for the hydrolysis are evaluated and discussed. A sensitive method for the determination of iron (III) in trace levels using fluorescence spectroscopy was devised. The method is based on the oxidation of di-2-pyridylketonebenzoyl hydrazone by hydrogen peroxide whereby Fe (III) shows an inhibition effect on the emission signal. The detection limit of Fe (III) was found to be 3.0x10-6M. Interference studies and order of addition were also investigated. The method was successfully applied to milk and other medicinal samples.
HPLC Determination of Four Textile Dyes and Studying Their Degradation Using Spectrophotometric Technique
In the present work, a simple and a sensitive HPLC method was developed for quantitative determination of four Direct textile dyes (Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34). The maximum absorbance value for the above mentioned dyes were found to be at 510 nm, 607 nm, 484 nm and 411 nm, with retention times of 15.4, 8.8, 5.8 and 12.7 min, respectively. The mobile phase used was consisting of acetonitrile: water (60:40, v/v) containing 0.45 M N-cetyl-N,N,N-trimehyl ammonium bromide (CTAB). RP C18 column was used with a flow rate of 0.5ml/min. Calibration graphs were found to be linear over the ranges of 0.3–10ppm, 10–30ppm, 0.5–10ppm and 1–12ppm for Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34, respectively, with limit of detection 0.3ppm, 10ppm, 0.5ppm and 1ppm. The relative standard deviations (RSD%) were found to be 0.92 %, 0.83 %, 1.13 % and 0.34 %, respectively (n=3) with concentrations of 10ppm of each dye. The effect of pH, CTAB concentration and acetonitrile: water ratios (v/v) in the mobile phase on the determination of the four Direct azo dyes were investigated. The reducing degradation kinetics of the four Direct dyes; Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34 by zero– valent iron and aluminum metals in aqueous solutions were studied. Effective degradation was achieved when using Al compared to Fe. The results show that the rate of degradation is affected by acidity, amount of iron and aluminum, temperature and speed of solution agitation. The effect of metals nature on degradation of the four Direct azo dyes was studied. The following metals were used in this study (Mn, Ni, Co, Zn, Mg and Cu). The obtained results showed that using Cu do not effects on degradation rate, where using Al, Mg give a higher degradation rate compared to iron.
Kinetic Studies of the Hydrolysis of Furfurylidenefuroyl Hydrazone Derivatives, Solvatochromism and Fluorimetric Determination of Iron (III)
Abstract
Preferential solvation of di-2-pyridylketonebenzoyl hydrazone was investigated in aqueous-ethanol binary mixtures .
The kinetics and mechanism of the hydrolysis of a series of substituted furfurylidenefuroyl hydrazones (X-FFH) in 25% (v/v) ethanol-buffer mixtures have been studied by ultraviolet visible spectrophotometry at different temperatures in the range 22-500C. The hydrolysis reactions were found to follow first-order kinetics. The effect of pH, molecular structure and temperature on the rate of hydrolysis have been discussed.
A mechanism for the hydrolysis is postulated in which the attack of water on the protonated substrate is subject to general acid-base catalysis using HCl-sodium acetate buffer solution. The hydrolysis of 5-Chlorothiophenylidene salicoyl hydrazone (CTSH) was found to obey specific acid catalysis using HCl-KCl buffer solutions.
The observed rate constants and the catalytic rate constants with respect to H+, HC2O4- and H2C2O4 were calculated. Activation energy and thermodynamic parametres for the hydrolysis are evaluated and discussed.
A sensitive method for the determination of iron (III) in trace levels using fluorescence spectroscopy was devised. The method is based on the oxidation of di-2-pyridylketonebenzoyl hydrazone by hydrogen peroxide whereby Fe (III) shows an inhibition effect on the emission signal. The detection limit of Fe (III) was found to be 3.0x10-6M. Interference studies and order of addition were also investigated. The method was successfully applied to milk and other medicinal samples.
Recyclable Pd (II) Catalysis on Polymer and Natural Products Supports
Abstract Three palladium-complexed compounds were prepared and applied successfully in catalyzing many reactions such as Heck and Wacker reactions and also used in carbonylation of olefin. Polymeric polyimine palladium catalyst 12 was prepared from palladium metal immobilized on a polyimine polymer11. This polymer was prepared by condensation of a dialdehyde (1,4benzenedicarboxaldehyde 10) and diamine (ethylene-diamin). Then Palladium metal was introduced on the polymer to give the catalyst. The prepared polymer catalyst was used in synthesis of 2-hydroxy cycloketones and 2-methoxycycloketones as follows: 2-hydroxy cyclohexanone 15 from cyclohexanone, 2-methoxycyclohexanone 31 from cyclohexanone, and α-hydroxy acetophenone 16 from acetophenone. The products were characterized spectroscopicaly using GC, NMR, IR as well as elemental analysis. The used complex catalyst was reused in the second and third catalytic cycle after washing it with toluene. The reactivity of the catalyst was not diminished in the second and third cycle. However we failed to estimate the percent of Pd remained in the complex after the third usage. In the second part of this work we prepared two complexes from the cheap starting material Curcumin 6. Curcumin, a natural product, along with two other curcuminoids 7 and 8 were extracted from turmeric. The mixture obtained was 3.57g (11.3% yield). The majority of this yield (88% curcumin ) was reduced in the presence of Pd/H2, to THC 24 which then reacted with 2 equivalents of benzylamine to give THCDBI 25 and then palladium was introduced on it. Pd+2 was prepared from oxidation of palladium sponge Pd0 in the presence of acetonitrile, nitrosonium tetrafluoroborate salt and freshly distilled acetonitrile. The reacture mixture was carried out with stirring under N2 to give a yellow golden solid. The yellow solid was filtered, washed with hexane, and dried under vacuum. The produced complex Pd (II)-THCDBI 26, was used to convert cyclopentanone to α-hydroxycyclopentanone 30,cyclohexanone to 2-hydroxycyclohexanone 15, 2-methylcyclohexanone to 2-hydroxy-6-methylcyclohexanone 33 and Propiophenone to 2-hydroxypropiophemone 35. All of the prepared products were characterized spectroscopically using GC, NMR, IR as well as elemental analysis. In the third part, we prepared the last complex which is THCDI-Pd complex 28. THC 24 was reacted with excess ammonia gas to produce light brown solid in 87% yield which turned out to be Tetrahydrocurcuminoids imine (THCDI) 27. Compound 27 was analyzed by 1H and 13C NMR. In the last step of the synthesis, palladium ion Pd+2 was introduced into the curcumin-imine compound (THCDI) to form the complex THCDI-Pd 28. The IR spectral data indicate the presence of Pd in the new complex since the band for C=N dropped by 35 cm-1. This drop is due to the formation of Pd-N bond and as a result of back bonding from 4d orbitals of the metal to the empty *π of the C=N bond, and so the bond order of C=N decreased causing the IR frequency to shift down. The prepared complex Pd (II)- THCDI 28 was used in the synthesis of 2-hydroxycyclohexanone 15, 2-hydroxy,6-methyl-cyclohexanone 33, and 2-hydroxypropiophemone 35. All of the spectroscopic analysis were in agreement with the results; however, we failed to calculate exactly the amount of Pd metal left in the residue for the polymeric complex. On the other hand we prepared and applied successfully the polymeric complex and hence a recyclable and environmentally friendly complex became possible.
Photocatalytic Degradation of Organic Contaminants in the Presence of Graphite-Supported and Unsu
ABSTRACT ZnO is a wide-band gap (3.2 eV) semiconductor, with limited photo-catalytic applications to shorter wavelengths only. However, it is suitable to use in solar light photo-degradation of different contaminants, due to a number of reasons, taking into account that the reaching-in solar radiation contains only a tail in the near UV region. The high absorptivity of ZnO makes it efficient photo-catalyst under direct solar light. Moreover, it is relatively safe, abundant and non costly. In this research, ZnO has been investigated as a potential catalyst for photo-degradation of methyl orange (a known dye) and phenazopyridine in aqueous solutions with direct natural solar light under different conditions. Xe lamp was used in a number of experiments. The major aim was to assess the efficiency and stability of ZnO under photo-electrochemical (PEC) conditions, and to suggest techniques to enhance such features. This will shed light on the future applicability of ZnO as a candidate for economic and friendly processes in water purification. Recovery of ZnO particles, after reaction completion, has been facilitated by supporting ZnO onto activated carbon, to yield AC/ZnO system. The AC/ZnO was used as catalyst for contaminant photo-degradation in water solutions under direct solar light. Both catalytic systems, naked ZnO and AC/ZnO, were highly efficient in degrading both contaminants, reaching complete removal in reasonable times. The latter system showed higher efficiency. In both systems, the reaction goes faster with higher catalyst loading, until a maximum efficiency is reached at a certain concentration, after which the catalyst concentration did not show a systematic effect. In both catalytic systems, the rate of degradation reaction increases with higher contaminant concentrations until a certain limit is used. The contaminant degradation reaction was studied, using both catalysts, at different pH values. The pH value 8.0 gave the highest catalyst efficiency. The tendency of naked ZnO to degrade into soluble zinc ions, under photo-degradation experiments, was studied under different pH values. Catalyst recovery and reuse experiments were conducted on both systems. The catalytic activity of the recovered systems was only slightly lower than the fresh system in each case. The fourth time recovered catalysts showed a considerable efficiency loss in each case, except when ZnO/AC system was used to photo-degrade MO, presumably due to ZnO degradation and leaching out. However, fresh and recovered catalyst systems caused complete degradation of contaminants after enough time. Temperature showed a slight effect on rate of reaction, with immeasurably small activation energy value. Details of effects of other parameters on reaction rate and catalyst efficiency are described. Using CdS as sensitizing dye failed to enhance ZnO efficiency under direct solar light. The screening effect and tendency of CdS to leach out limit its use as ZnO sensitizer. Tendency of ZnO to leach out zinc ions into solution is discussed. The naked ZnO and AC/ZnO systems are promising photo-catalysts in future water purification technologies by direct solar light.
Spectophotomertic studies of Anionic Surfactant Absorption of Total Petroleum Hydrocarbon Using Soil in a Column Chromatography
Abstract
Surfactant with its amphiphilic nature toward polar and nonpolar substances may be used in mass transfer improvement of hydrophobic pollutants from solid or non-aqueous liquid phase into aqueous phase by decreasing interfacial tension and formation of micelles which surround these pollutants and solubilize them into aqueous phase. Micelles are often characterized according to their size and shape. The geometric properties of these micelles depend on the chemical structure of the surfactant and on the concentration and the nature of the aqueous environment. The adsorption of the surfactant on solid surfaces can lower the concentration of free surfactant in aqueous solution. If the degree of adsorption is high, surfactant concentration could drop below the Critical Micelle Concentration (CMC), rendering the surfactant solution with no ability to solubilize. Therefore, the amount of surfactant mass that will sorb should be accounted for when selecting injection concentration. In this study, diesel was used as an organic contaminant to study sorption characteristics of non ionic surfactant, Triton X-100 onto soil below and above CMC. The surface tension measurement was used for calculating this kind of sorption. Nonionic surfactant Triton X-100 was used to study remediation enhancement of diesel contaminated soil. UV-Visible Spectrophotometer was used to determine the amount of diesel removed from contaminated soil by surfactant via solubilization and mobilization mechanisms at 254 nm. The results indicated that when the concentration of surfactant was lower than the CMC, the amount of surfactant sorbed on soil increased with increasing the surfactant concentration; the amount of desorbed diesel was relatively low compared with the original amount added to soil, but amount of diesel desorbed from soil at surfactant concentration above CMC was relatively high. Other factors such as temperature, pH, and ionic strength were also studied to examine whether they improve or inhibit diesel desorption from soil. The study has shown that high pH, low pH, high temperature, and ionic strength decreases the capacity of surfactant in desorption of diesel from soil.
HPLC Determination of Four Textile Dyes and Studying Their Degradation UsingSpectrophotometric Technique
Abstract
In the present work, a simple and a sensitive HPLC method was developed for quantitative determination of four Direct textile dyes (Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34).
The maximum absorbance value for the above mentioned dyes were found to be at 510 nm, 607 nm, 484 nm and 411 nm, with retention times of 15.4, 8.8, 5.8 and 12.7 min, respectively.
The mobile phase used was consisting of acetonitrile: water (60:40, v/v) containing 0.45 M N-cetyl-N,N,N-trimehyl ammonium bromide (CTAB). RP C18 column was used with a flow rate of 0.5ml/min.
Calibration graphs were found to be linear over the ranges of 0.3–10ppm, 10–30ppm, 0.5–10ppm and 1–12ppm for Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34, respectively, with limit of detection 0.3ppm, 10ppm, 0.5ppm and 1ppm. The relative standard deviations (RSD%) were found to be 0.92 %, 0.83 %, 1.13 % and 0.34 %, respectively (n=3) with concentrations of 10ppm of each dye. The effect of pH, CTAB concentration and acetonitrile: water ratios (v/v) in the mobile phase on the determination of the four Direct azo dyes were investigated.
The reducing degradation kinetics of the four Direct dyes; Direct Red 81, Direct Blue 15, Direct Black 22 and Direct Orange 34 by zero– valent iron and aluminum metals in aqueous solutions were studied. Effective degradation was achieved when using Al compared to Fe. The results show that the rate of degradation is affected by acidity, amount of iron and aluminum, temperature and speed of solution agitation.
The effect of metals natu
I-Determination of Lead and Cadmium in Food
In part (І) trace metal concentrations in food, cigarettes and water was determined. Reprehensive samples were taken during May- August 2003. Food samples were digested and then analyzed for their contents of lead and cadmium. Samples were analyzed using anodic stripping voltammetry, which considered being sensitive compared to other methods used in determination of heavy metals.
The results showed very low concentrations that were below the safe limits of lead and cadmium set by the WHO. In part (ІІ) reaction of galactose with potassium hexacyanoferrate (ΙΙΙ) in alkaline medium was studied at constant temperature and ionic strength. Stoichiometric studies showed that for each mole of galactose oxidized, two mole of potassium hexacyanoferrate (ΙΙΙ) were reduced to produce galactonic acid.
The dependence of rate on the concentration of each of galactose, heacyanoferrate (ΙΙΙ) and hydroxide ion was determined. The reaction followed first order rate dependence on both; galactose and hydroxide ion and the rate was independent of
Full Article
Voltammetric and HPLC Determination of
Simple and sensitive voltammetric and HPLC methods were developed for the determination of the three azo dyes (Acid Orange 7, Acid Orange 10 and Acid Orange 12). Optimization of various experimental conditions for quantitative determination of dyes is described.
The voltammetric method for determination of trace amounts of dyes is carried out by differential pulse-adsorptive cathodic stripping voltammetry (DP-AdCSV) technique at a hanging mercury drop electrode (HMDE). The effects of different parameters that influence the (DP-AdCSV) response are described. These parameters include pH, accumulation potential, accumulation time, pulse amplitude, scan rate, drop size and interference by other ions.
The calibration graphs for the determination of the studied dyes were linear in the range 0.004-0.105 ppm, 0.009-0.180 ppm and 0.007-0.140 ppm with detection limit
Adsorption and desorption characteristics of endosulfan pesticide from three soils in Palestine)
Abstract
In this thesis adsorption and desorption features were studied in details in three samples from the soil of Palestine. Soil samples were red soil, chalk soil, and sandy soil according to American Society for Testing and Materials (ASTM) scale for the classification of the soil. Adsorption and desorption rates on soil samples were calculated from kinetic studies. The values varied based on the type of soil.
Maximum specific adsorption capacities (qmax) for soil samples using Langmuir model, were as follows: 0,387 (red soil), and 0,281
(chalk soil), and (0.075) sandy soil mg / g of endosulfan.
Maximum adsorption was measured in red soil followed by chalk soil, but it was the least for the sandy soil. Also, the proportion of organic matter play a major role in both processes adsorption and desorptio on soil samples.
_SetupBidi('source'); here was a significant reduction in the process of Adsorption in soil samples compared with the decline in pH. Desorption was higher at both acidic and alkaline pH ranges compared to neutral pH. Both the increase in temperature and concentration increase the adsorption and desorption in all soil samples.
Finally, the results showed that the mobility of endosulfan, is more possible in the sandy soil followed by red, followed by chalk soil This may be attributed to the crystal lattice of red soil that play an important role in both processes adsorption and desorption, as it could be a major role for chemical and biological processes that play a role in the other soil samples.
Chromatographic and Spectrophotometric Determination of Some Direct TextileDyes Before & After their Degradation
In the present work, simple and sensitive HPLC method was developed for quantitative determination of four direct dyes (Direct Blue 2, Direct Red 23, Direct Green 1 and Direct Yellow 12). The maximum absorbance values for the above-mentioned dyes were found to be at 574 nm, 508 nm, 603 nm and 399 nm, with retention times of 2.9, 5.7, 6.1 and 6. 7 min, respectively. The mobile phase used was consisting of acetonitrile: water (60:40, v/v) containing 0.45 M Nــ cetyl ــN,N,N ــtrimethyl ammonium bromide (CTAB). RP C18 column was used with a flow rate of 0.5 ml/ min. Calibration graphs were found to be linear over the range 0.5-10 ppm for each of Direct Blue 2, Direct Red 23 and Direct Green 1 and 0.5-20 ppm for Direct Yellow 12. The relative standard deviation values were found to be 1.79%, 0.90%, 1.20% and 0.30% for the above-mentioned dyes, respectively. The effect of pH, flow rate of mobile phase and the concentration of CTAB on the determination of the four dyes have been investigated. The degradation kinetics of the four diazo dyes, Blue 2, Direct Red 23, Direct Green 1 and Direct Yellow 12 by iron metal in aqueous solution were studied. The results show that the rate of degradation is affected by the acidity, surface area of iron and temperature of the solution. The rates of degradation of the four dyes in aqueous solutions in presence of different metals (Co, Cu, Ni, Mn, Zn, Al and Fe), using UV light were studied. The obtained results showed that the rate of degradation was highest in the presence of aluminum metal and the rate of degradation was found to be higher when degradation was accompanied by exposure to UV light.