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- Author or Editor: M. Ramadan x
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Abstract
Chemical factors such as pH, concentration and temperature affecting the removal of UO2 2+, Th4+, Fe3+, Cu2+, Pb2+,Cd2+, Ni2+, MnO4 - and phenol by Eichornia crassipes aquatic plant from their solutions were examined. Maximum uptake of ions by Eichornia crassipes occurred at pH 4 to 6±0.5 at 25±3 °C. An initial rapid uptake phase for the first 6 hours followed by a slower near linear one was observed. One gram of Eichornia crassipes can accumulate about 25 mg UO2 2+, 5 mg Th4+, 30 mg Fe3+, 10 mg MnO4 -, 15 mg Cu2+, 1.0 mg Pb2+, 1.5 mg Ni2+, 0.7 mg Cd2+ and or 25 mg of phenol.
Abstract
A stone of brick-like shape, measuring roughly 25×12.5×10.5 cm3 and weighing 14 kg was found in 1983, in the western desert of Egypt. The meteorite was named El-Bahrain meteorite and classified as L-chondrite. In the present paper, the principal constituents of El-Bahrain meteorite have been studied by means of Mössbauer spectroscopy. The chemical composition as obtained by the conventional wet analyses of L-chondritic meteorites showed that the meteorite contains 23.38% Fe and 1.23% Ni. While the analysis of the atomic absorption showed the presence of 27.03% as a total iron. The Mössbauer analysis of El-Bahrain meteorite showed that the iron constituent minerals were determined to be olivine, metallic iron-nickel alloys (kamacite, taenite and tetrataenite), ferrous sulfide (troilite) and weathering products such as maghemite and nanocrystalline hematite. The structure of meteoritic iron obtained by the Mössbauer analysis has been discussed on the basis of these constituents.
Abstract
The extraction of Eu(III) by dinonylnaphthalenesulfonic acid (HDNNS) in benzene from nitrate and perchlorate solutions has been investigated. For nitrate solutions the ionic strength of the aqueous phase was kept constant at 0.1M using NaNO3–HNO3 mixtures. The Eu distribution was measured at different temperatures. The following stoichiometric formulae for the Eu species in benzene were derived: Eu(NO3) (Hn–1 (DNNS)n)2 and Eu(Hn–1 (DNNS)n)3, from the nitrate and perchlorate medium respectively (n being a small number, e.g. 1, 2 or 3). The equilibrium constants were calculated and the thermodynamic parameters of the system were determined. When adding dibenzo-24-crown-8, dicyclohexyl-18-crown-6 or trioctylphosphine oxide, no synergism, but rather antagonism was observed.
Abstract
The mechanism of the decomposition of the entitled compounds and their complexes is studied. Adenine, its Schiff base of salicylaldehyde, and its azo resorcinol derivatives are ended with carbon. However, oxalonitrile compound is appeared as a final product for adenine acetylacetone and an intermediate for adenine. The thermodynamic parameters of the decomposition reaction were evaluated and discussed. The change of entropy values, ΔS #, showed that the transition states are more ordered than the reacting complexes. The thermal processes proceed in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H2O, NH3, or HCl. In most cases, the free radical species of the ligands are assigned to exist through decomposition mechanisms. The copper adenine and nickel salicylaldehyde complexes are ended with the metal as a final product. However, the cobalt adenine, its acetylacetone, its salicylaldehyde, cadmium and mercury guanine complexes are ended with metal oxides.
Two sensitive, specific, and selective stability-indicating chromatographic methods were developed for the determination of cyclobenzaprine HCl (CZ) and asenapine maleate (AS) in pure forms, in the presence of their degradation products and in their pharmaceutical formulations. The first method was an isocratic reversed-phase high-performance liquid chromatography (RP-HPLC). Analysis was performed on cyano column using a mobile phase consisting of acetonitrile–(0.05 m) potassium dihydrogen phosphate buffer (pH 3 ± 0.1) (70:30, v/v) with a flow rate of 1.5 mL min−1 and ultraviolet (UV) detection at 290 nm for the determination of CZ, and methanol–(0.05 m) potassium dihydrogen phosphate buffer (pH 6 ± 0.1) (70:30, v/v) with a flow rate of 1.5 mL min−1 and UV detection at 220 nm for the determination of AS. The second method was thin-layer chromatography (TLC), using silica gel 60 F254 plates and toluene–methanol–chloroform-ammonia solution 33% (5:3:6:0.1, by volume) as the mobile phase for the two drugs. The spots were scanned densitometrically at 290 and 220 nm for the determination of CZ and AS, respectively. The methods were validated according to the International Conference on Harmonization (ICH) guidelines, and the acceptance criteria for linearity, accuracy, precision, specificity, and system suitability were met in all cases. The linearity ranges were 2.5–25 μg mL−1 for the RP-HPLC method and 5–50 μg band−1 for the TLC method for both drugs. The limits of detection for the RP-HPLC method were 0.250 and 0.578 for CZ and AS, respectively, while the limits of quantification were 0.758 and 1.572 for CZ and AS, respectively. The limits of detection for the TLC method were 1.355 and 1.284 for CZ and AS, respectively, while the limits of quantification were 4.472 and 3.891 for CZ and AS, respectively. The results were compared statistically at a 95% confidence level with the reported methods. There were no significant differences between the mean percentage recoveries and the precisions of the two methods.
Abstract
Monitoring benzoylphenylureas (BPUs) residues in ready-to-eat vegetables is of great interest for an adequate assessment of human pesticide exposure. A rapid, inexpensive, simple, and effective method for determining 8 BPUs insecticides in tomatoes and cucumbers was developed and validated. Vortex-assisted liquid-liquid extraction (VA-LLE) followed by dispersive solid-phase extraction (d-SPE) using graphitized carbon black (GCB) for cleanup was used before LC-MS/MS analysis. Different parameters were optimized, including the type and volume of extractants, vortex time, and the type and amount of adsorbents used for cleanup. The evaluation showed that the method has excellent linearity (R 2 ≥ 0.994). The recovered 8 BPUs insecticides from spiked tomato and cucumber samples at 0.01, 0.05, and 0.25 mg kg−1 ranged from 83.2 to 105.2%, with RSD of 4.9–14.6%. The limits of quantitation (LOQs) were 0.0025 mg kg−1 (0.005 mg kg−1 for lufenuron). Within-day repeatability ranged from 3.9 to 13.9%, while between-day repeatability ranged from 8.9% to 17.7%. The optimized method was used to analyze 100 samples of tomatoes and cucumbers marketed in Saudi Arabia.
