Mohammed A. Zaitoun

Heavy Metal Contamination of Soil, Plant and Air of Scrapyard of Discarded Vehicles at Zarqa City, Jordan

Ninety soil samples, forty plant samples (Anabasis articulata), and twenty air samples were collected from the scrap yard of discarded vehicles near Zarqa city, Jordan. These samples were analyzed for heavy metals: Cd, Pb, Zn, Cu, Mn, Al, and Fe. Longitudinal and vertical profiles of soil samples were studied. Generally, the levels of all heavy metals studied in the scrap yard area were found to be higher than those of the control samples. The levels of heavy metals decreased with depth until reaching a constant value at 9 cm depth. The levels of heavy metals also decreased at distances farther away from the scrap yard area. A significant difference in heavy metal concentrations was found between washed and unwashed plant samples. On the other hand, no significant differences have been found between plant samples from inside and outside the scrap yard area. Air samples showed wide variations in heavy metal levels among the sampling sites. The enrichment factors for non-crustal elements such as Pb, Cd, Cu, and Zn, in both soil and particulate matter, were found to be more than 10, indicating anthropogenic sources such as dust, rust, and exhaust emissions from the scrap yard area, whereas the crustal elements such as Fe and Mn showed enrichment factors of less than 10.

Glucose biosensor based on entrapment of glucose oxidase and myoglobin in silica gel by the sol-gel method

A spectrophotometric method is presented to determine glucose employing the sol-gel technique. Myoglobin (Mb) and glucose oxidase are encapsulated in a transparent and porous silica glass. The produced gel (xerogel) is then immersed in water where increments of glucose are added to the solution with stirring; glucose diffuses into the sol-gel glass pores and a series of reactions take place. Glucose is first oxidized by glucose oxidase and oxygen to gluconate and hydrogen peroxide is generated. The liberated hydrogen peroxide oxidizes the Mb heme (Fe 2+ into Fe 3+ ). The higher is the glucose concentration added, the more is the H2O2 generated, and the more is the Mb oxidation (Fe 2+ to Fe 3+ ) and as a result the higher is the absorbance at 400 nm (negative peak, lower absorbance value). All measurements are performed at this wavelength (400 nm), the negative peak obtained by subtracting the absorption spectra of Mb before and after oxidation. Measuring the slope of the absorbance decay versus time at 400 nm monitors increments of added glucose. Each glucose concentration has an accompa- nying unique decay curve with a unique slope. The higher is the glucose concentration; the steeper is the decay curve (higher slope value). The calibration curve was linear up to 40 mM.

Enhancement of Eu3+ emission in solution by bulky chelating ligands and deuterium substitution

Binding the europium ion with a bulky chelating ligand provides one strategy for minimizing the quenching effects of water on the luminescence of the ion. 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraaceticacid tetrahydrochloride (TTT) was used as a chelating agent to isolate Eu 3+ from hydroxyl deactivation in water. A large enhancement in the Eu 3+ emission was observed for the chelated Eu 3+ compared to the unchelated. Absorption and emission spectra are reported together with lifetime measurements. The latter were used to study concentration quenching and quenching by water.

A kinetic-spectrophotometric method for the determination of glucose in solutions

A kinetic-spectrophotometric method is proposed to determine glucose in solutions. Measurements were performed at 400 nm; the negative peak was obtained by subtracting the absorption spectra of myoglobin (Mb) before and after oxidation. In this method, glucose is added to a mixture of Mb and glucose oxidase. Glucose is oxidized by glucose oxidase and oxygen to gluconate and hydrogen peroxide is generated. The liberated hydrogen peroxide oxidizes the Mb heme (Fe2+) into Fe3+. The higher the glucose concentration added, the more the H2O2 generation, and the more the Mb oxidation (Fe2+ to Fe3+) and, as a result, the higher the absorbance at 400 nm (negative peak, lower absorbance value). The increments of added glucose are monitored by measuring the absorbance decay versus time (0–250 s) at 400 nm. Each glucose concentration has an accompanying unique absorbance value at 250 s. The higher the glucose concentrations, the lower the absorbance at 250 s (measured at 400 nm). The calibration curve for glucose was linear from 0.1 to 3.0 mM; the detection limit was found to be 0.025 mM. There was no interference from major substances present; the only interference was from species that react with H2O2 (ascorbic acid, uric acid, and urea) or that react with glucose (Cu2+ and Fe3+). Standard deviation in the determination was ±0.01 mM for a 1.3 mM glucose solution (n = 10).

Observation of Room-Temperature 5D1 Luminescence of an Organoeuropium Complex Encapsulated in Sol-Gel Glass

In comparing emissions of the inorganic Eu3+ salts (chloride or nitrate) to organoeuropium complexes doped into optically transparent sol-gel glass, previous studies have indicated that changes in the local chemical environment by chelation or variation of the ligand or gel matrix compositions were found to leave the main spectral features of Eu3+ essentially unchanged; complexation just increases the emission intensity of europium and leads to broadening and splitting of the peaks. In all cases studied and irrespective of the excitation energy, the observable emission peaks result only from relaxations out of the 5D0 excited state of Eu3+ to the first five levels of the 7F ground manifold. The present research examines the luminescence behavior of EuCl3 and Eu-TETA (TETA is the macro cycle, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraaceticacid) doped into a sol-gel host; in addition to emissions from the 5D0, emission from the 5D1 excited state of Eu3+ is observed for the first time.

Pr(III) luminescence enhancement by chelation in solution and in sol-gel glass.

Due to the weak emission of lanthanide ions in solution, it is common practice to form complexes of the lanthanide ions with organic ligands that strongly absorbs light and transfers the energy to the lanthanide ion center via the antenna effect. The organic ligands 2-6-pyridinedicarboxylate (L1) and the polytonic diazine (N-N) ligand L2 (C22H16N12O2) were used to synthesize two Pr(III) complexes, namely: Pr-L1 (Na3[Pr(C7H3NO4)3]) and Pr-L2. The prepared complexes were further encapsulated in an optically transparent sol-gel glass. The synthesized ligands and complexes were characterized by FTIR and (1)H NMR. Room temperature luminescence of Pr-L1 and Pr-L2 complexes in solution and in sol-gel glass were investigated using a spectrofluorometer. Excitation at the maximum absorption wavelength of the ligands (280nm) resulted in the typical visible luminescence (centered at around 600nm) resulting from the (1)D2→(3)H4 transition of the Pr(III) ion, which contributes to the efficient energy transfer from the absorbing ligand L1 to the chelated Pr(III) ion (an antenna effect) while the Pr(III) luminescence is not efficiently sensitized by ligand L2. The obtained emission spectra indicated that the excitation energy level for the central Pr(III) is in a slightly lower location than ligand L1 excitation triplet (T1) level and can accept the energy transfer from T1 efficiently.

Synthesis of an Organic Chelate Doped Sol Gel Filter to Remove Cu(II) Ions from Aqueous Solutions

A leaching free sol-gel glass resin was synthesized by doping 1-5-methyl-4-(2thiazolylazo)resorcinol (5-Me-TAR) ligand in an inert, optically transparent and porous sol-gel glass, the produced gel matrix was used in the solid phase extraction to remove Cu(II) from water samples. The doped ligand is dissolved in the liquid phase at the beginning of the preparation; by hydrolysis and condensation of the alkoxysilanes, a solid glass forms around the dopant. The ligand molecule is entrapped inside the glass pores while small Cu(II) metal ions can diffuse into the pores where they are complexed by the ligand and retained inside the pores. Absorption and fluorescence spectroscopy were used to characterize 5-Me-TAR ligand and 5Me-TAR-Cu complex both in solution and sol-gel glass. The sol-gel glass precursors were carefully selected to produce a glass composite material doped with the ligand with no leaching especially when the glass is soaked in solution. To study complexation/adsorption, the batch method was employed in which a known weight of the sorbent resin (glass containing the ligand) is mixed with a known concentration of Cu(II) ions. In order to attain the maximum metal ion complexation/adsorption capacity, these organically modified silica filters were optimized to the optimum separation/preconcentration conditions of analytes, including the kinetics, isotherm, effect of pH and shaking time; afterwards, the solution was filtered. The amount of copper metal ion complexed/adsorbed was determined by the difference between the initial concentration in aqueous solution and that found in the supernatant using a flame AA. With a loading of 0.013 g ligand per g of dry silica (0.055 mmol ligand per g), the sol-gel silica sorbent has a capacity of 0.053 mmol Cu/g. In all cases, applications to reference materials and to real environmental samples were investigated.