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Abstract  

Radon has been recognized to be one of the major contributors to the natural radiation causing even lung cancer if it is present at enhanced levels. Its monitoring at highly confined locations such as underground caves, mines and tube-wells is very essential for finding the health related hazards among the workers. This paper reports the investigations of the levels of radon, thoron and their progeny monitored in the tube-wells of the Halls of residence at A.M.U., Aligarh, which lies in the subtropical region of Indo-Gangetic plains situated in North India. The twin cup dosimeters were fixed for exposure at a depth of 5–35 feet with a difference of 5 feet from the ground surface. The values of radon and thoron concentrations were found to vary from 6.58 to 1218.57 and 7.41–3226.61 Bq m−3, respectively. The preliminary results of this study for ‘bare mode’ detectors have been separately published and compared with the recent data.

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Thermal analysis of pharmaceutical compounds

IV. Evaluation of sulphonamides by thermal analysis

Journal of Thermal Analysis and Calorimetry
Authors: Fatma I. Khattab, M. M. Amer, and Nagiba Y. M. Hassan

Some sulphonamides are evaluated by means of thermal analysis. Use is made of their characteristic endothermic DTA peaks (melting peaks), where the area changes linearly with variations in the amount of sulphonamides. The method is suitable for the determination of 30–100 mg of sulphathiazole, sulphisomidine, sulphaguanidine, sulphacetamide sodium and sulphamethoxypyridazine with reasonable accuracy. As for sulphisoxazole, two peaks are used for its determination: an endothermic one to determine 30–100 mg, and an exothermic one to determine 6–30 mg.

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Thermal analysis of pharmaceutical compounds

III. Characterization of sulphonamides by thermal analysis

Journal of Thermal Analysis and Calorimetry
Authors: F. I. Khattab, N. Y. M. Hassan, and M. M. Amer

Fourteen sulphonamides have been thermally analyzed using thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA). Their thermal reactions and stabilities have been thoroughly studied. It was found that the sulphonamides are first transformed into sulphanilamide. The melting points of these sulphonamides have been determined through their DTA curves and by the Kofler microscope, the results agreeing with those reported in the literature. The amount of water of crystallization has been calculated from the TG and DTG curves. Analysis of mixtures of some sulphonamides has been achieved by thermal analysis and by thin-layer chromatography using different solvent systems.

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Two novel, sensitive, and selective stability-indicating chromatographic methods were described for the analysis of zopiclone (ZOP) in the presence of its degradation products, namely, 7-oxo-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazin-5-yl-4-methylpiperazine-1-carboxylate (hydrolytic DEG) and 5H-pyrrolo[3,4-b]pyrazine-5,7(6H)-dione (oxidative DEG), in drug substance and product. The first method was an isocratic reversed-phase high-performance liquid chromatography (RP-HPLC) using Inertsil ODS3 (250 × 4 mm, 5 μm) column. Upon using HPLC, the run time could be reduced, and actually, the solvents consumption decreased. Quantification was achieved by detection wavelength at 237 nm, based on peak area. Chromatographic separation was performed over the range of 1–10 μg mL−1 with limits of detection (LOD) and quantification (LOQ) of 0.18 and 0.55 μg mL−1 and a mean recovery of 99.98 ± 0.55. The analysis was achieved at 30°C using a mixture of acetonitrile and water (50:50 v/v) as the mobile phase. The second method was thin-layer chromatography (TLC) applied for the separation and analysis of zopiclone in the presence of its alkaline, acidic, and oxidative degradation products. Chromatography was performed on silica gel 60 F254 plates with ethyl acetate‒methanol‒ammonia 33% (17:2:1 v/v) as the mobile phase. Successful resolution was observed with significant difference in the R F values, followed by densitometric measurement at 303 nm. Evaluation was carried out over the range of 0.1–2 μg per spot with a mean recovery of 100.52% ± 0.24. The developed methods were successfully applied to the analysis of ZOP in bulk powder, laboratory-prepared mixtures containing different percentages of its degradation products, and pharmaceutical dosage form. The degradation products were separated by HPLC as well as identified by TLC, infrared (IR), and mass spectrometry (MS) to confirm its structures and elucidate degradation pathway. The developed methods were validated as per the International Conference on Harmonization (ICH) guidelines. The results obtained by the proposed methods were statistically compared with the reported methods revealing high accuracy and good precision.

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Accurate, selective, and sensitive thin-layer chromatography (TLC)—densitometry and reversed-phase high-performance liquid chromatography (RP-HPLC) methods have been developed and validated for the simultaneous determination of vitamin E (VIT E) and vinpocetine (VINP) in the presence of the alkaline-induced degradation product of vinpocetine (DEG). The proposed TLC— densitometric method depends on the separation and quantitation of VIT E, VINP, and VINP alkaline-induced degradation product on TLC silica gel 60 F254 plates, using methanol—chloroform—ethyl acetate—glacial acetic acid—ammonia solution (6:2:2:0.5:0.1, by volume) as the developing system followed by densitometric measurement at 235 nm. The studied components were well resolved from each other with significantly different R f values of 0.81, 0.62, and 0.41 for VIT E, VINP, and DEG, respectively. On the other hand, the developed RP-HPLC method was based on the separation of the studied components using 0.05 M KH2PO4 (adjusted to pH = 3) and methanol in gradient elution mode on C8 column at a flow rate of 1.5 mL min−1 and ultraviolet (UV) detection at 235 nm. The studied components were well resolved from each other with significantly different R t values of 10.90, 2.89, and 1.90 min for VIT E, VINP, and DEG, respectively. The developed methods were validated according to the International Conference on Harmonization (ICH) guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by the reported method, and no significant difference was found. The developed methods are the first developed stability-indicating assay methods (SIAMs) for the analysis of the studied binary mixture.

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Abstract  

The effect of water-miscible alcohols and acetone on the extraction and separation of Cd and Zn chlorides by TOPO was systematically investigated. The maximum extraction of Zn chloride with 0.1 M TOPO decreases in the order: acetone>methanol>ethanol>2-propanol>2-butanol. For alcohols, the sequence of decreasing extractability is thus parallel to the order of their dielectric constants. This can be explained by the increase of HCl extraction by TOPO in the same direction. The presence of additives in the polar phase prevents the formation of a bulky white precipitate encountered during extraction of ZnCl2 from pure aqueous solutions. A decrease of Cd chloride extraction was generally noticed in presence of additives; this is more noticeable for the longer chain alcohols. The highest separation factor (E for ZnCl2 and CdCl2 in 0.48M HCl is obtained from 30% methanol (13.8 compared to about 3.8 in absence of methanol) and from 10–20% acetone where it reaches 30.

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Eight compounds were isolated and identified from the soil-inhabiting fungus Aspergillus fumigatus 3T-EGY, namely, stearic acid (1), α-linolenic acid (2), physcion (3), di-(2-ethylhexyl) phthalate (4), 2,4,5,17-tetramethoxy pradimicin lactone (5), 3,5-dihydroxy-7-O-α-rhamnopyranoyl-2H-chromen-2-one (6), juglanthraquinone A-5-O-d-rhodosamine-(4′→1″)-2-deoxy-d-glucose (4″→1″′)-cinerulose B (7), and micropeptin (8). Their structures were determined on the basis of one-dimensional (1D-) and two-dimensional nuclear magnetic resonance (2D-NMR) [1H-, 13C-NMR, 1H-1H COSY (COrrelated SpectroscopY), and 1H-13C HMBC (Heteronuclear Multiple Bond Correlation) spectroscopy]. Compound 7 showed moderate in vitro antimicrobial activity against three pathogenic strains with inhibition zones values were ranged from 9.0 to 10.66 mm compared to neomycin as a positive control with inhibition zones values were ranged from 14.0 to 19.0 mm.

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Abstract  

Water hyacinth (Eichhornia crassipes) is known to accumulate elements from rivers and a good tool for water monitoring. To test the usefulness of such an aquatic plant as a bioindicator, we have determined the levels of Na, Ca, Cr, Fe, Co, Zn, As, Rb, Zr, Sb, Cs, La, Ce, Nd, Sm, Eu, Tb, Yb, Hf, Ta, Th, and U in water hyacinth around industrial facilities and along the studied area by instrumental neutron activation analysis. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb were determined in upstream river water and effluent factories. Contamination factor, and pollution load index was calculated. The results show that higher concentrations as well as bioaccumulation factors of these elements were observed in water hyacinth samples around the industrial facilities. On the other hand a decrease in calcium concentration was observed as a result of the thermal pollution of Nile river water. The pollution load index for the studied area was estimated to be 4.2.

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Abstract

A sensitive RP-HPLC method is presented for the simultaneous quantification of Fluorometholone (FLM) and Tetrahydrozoline hydrochloride (THZ). The method has the advantages of being rapid, accurate, reproducible, ecologically acceptable and sensitive. The separation utilized C8 Xbridge® column and mobile phase mixture of Acetonitrile/phosphate buffer pH 3 ± 0.1 (70:30, v/v) with UV detection at 230 nm. Stepwise optimization and factors affecting separation are properly discussed. Different factors were optimized such as stationary phase, selection of organic solvent and its content, buffer pH and concentration, flow rate, elution type and detection wavelength. The studied drugs were efficiently separated in 3.4 min with high resolution. Also, two univariate spectrophotometric methods have been optimized for the quantification of the studied drugs. Method 1: dual wavelength for THZ and iso-absorptive point for FLM, Method 2: ratio difference (RD) for THZ and first derivative FLM utilizing methanol as a solvent. These methods are accurate, precise with minimal data manipulation. Greenness of the methods was estimated using eco-scale tool where the presented methods were found to be excellent green with eco-score of 83 for HPLC and 80 for spectrophotometry. The methods are validated in conformance with ICH guidelines, with acceptable accuracy, precision, and selectivity. The suggested methods can be employed for the economic analysis of THZ and FLM in their pure form and binary ophthalmic formulation, that can be employed by quality control laboratories.

Open access
Reaction Kinetics, Mechanisms and Catalysis
Authors: Shakeel Ahmed, Faizur Rahman, Adnan M. J. Al-Amer, Eid M. Al-Mutairi, Uwais Baduruthamal, and Khurshid Alam

Abstract

A series of metal incorporated M-MCM-41 (M = Ce, Mo, and/or V) mesoporous materials were synthesized by the hydrothermal method. The synthesized mesoporous materials were characterized by the XRD, BET, TPR and EPR techniques. The extent of mesoporous structural ordering was evident from the XRD pattern of M-MCM-41. The catalytic properties of the metal containing MCM-41 catalysts were evaluated for oxidative dehydrogenation of propane and n-butane in a fixed-bed micro-reactor. The results showed higher activity in case of V-MCM-41 catalyst as compared to that of Mo-MCM-41 catalysts over a temperature range of 500–600 °C at atmospheric pressure. Cerium containing MCM-41 catalyst showed high selectivity (78%) for butadiene at moderate conversion of about 4%. The major products include ethylene, propylene and butanes. Propane conversion of about 20% with corresponding propylene selectivity of around 30% was obtained at 575 °C over V-MCM-41 catalyst. A small amount of H2 besides COx was also produced during catalytic runs under the conditions of catalyst performance evaluation.

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