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Abstract
A simple and reliable method for the selective extraction and determination of uranium in water using octadecyl-bonded silica membrane disks modified with bis (2-ethylhexyl) hydrogen phosphate and alpha-spectrometry is described. Extraction efficiency and influence of sample matrix, optimum amount of extractant, type and minimum amount of organic eluent and flow rates were evaluated. The limit of detection of the proposed method is 40 ng per 1000 ml. The influence of potential interfering cations in water samples on the recovery of U(VI) was investigated. The method was successfully applied to the extraction and determination of uranium in natural water.
Abstract
Organoclays are the adsorption products of organic matter by clay minerals. In modern technology, organoclay-based nanocomposites obtained by modifying Na-clay by primary adsorption of organic ammonium cations or long-chain cationic surfactants are widely used in different industries. They are potential candidates for serving as sorbents of different organic compounds by secondary adsorption. Organoclays are widely spread in the environment and are responsible for the colloid behavior of different environmental elements such as soils. This manuscript summarizes some of the basic knowledge on thermal analysis of organoclays and reviews some of the recent studies carried out in our laboratory on organoclays which occur in the environment, those applied in industry and of those obtained by secondary adsorption processes. Complexes in the environment or those used in industry are mainly of the smectite clay mineral montmorillonite and their thermal analysis in air is treated here.
Abstract
The contributions of William D. Ehmann to radioanalytical chemistry and education in radiochemistry are summarized, and a selected bibliography of his publications is presented.
Abstract
Due to the interesting anti-proliferative properties of gallium-thiosemicarbazone complexes, the production of [67Ga]labeled 2-acetylpyridine 4,4-dimethyl thiosemicarbazone (APTSM2) was investigated. The freshly prepared [67Ga]GaCl3 was mixed with 2-acetylpyridine 4,4-dimethyl thiosemicarbazone for 60 minutes at 90 °C to yield [67Ga]APTSM2 with a radiochemical yield of more than 98%. Radio-thin-layer-chromatography (RTLC) showed a radiochemical purity of more than 99%. A specific activity of about 370–740 MBq/mmol (10–20 Ci/mmol) was obtained. The stability of the final product was checked in the absence and presence of human serum at 37 °C. The partition coefficient of the final complex was also determined. The biodistribution of the labeled compound in normal rats was compared with that of free Ga3+ cation up to 22 hours.
A simple, rapid, and selective densitometric thin-layer chromatographic (TLC) method has been established and validated for simultaneous quantitative analysis of olmesartan medoxomil and hydrochlorothiazide in the presence of olmesartan medoxomil degradation products. Chromatography was performed on aluminum foil-backed HPTLC plates coated with 0.2 mm layers of nano-silica gel 60 F254 as stationary phase. R F values of olmesartan medoxomil, its degradation products, and hydrochlorothiazide were significantly different when chloroform-methanol-formic acid 8:1.5:0.5 (v/v) was used as mobile phase. Detection was performed at 260 nm and 272 nm for olmesartan medoxomil and hydrochlorothiazide, respectively. Regression plots revealed good linear relationships in the concentration range 0.05–1 mg mL−1. Accuracy was checked by conducting recovery studies; average recovery was 100.35 ± 1.060 and 99.91 ± 1.154 for olmesartan medoxomil and hydrochlorothiazide, respectively. The amounts of the drugs in the dosage formulation were 102.78 ± 1.525% of the label claim for olmesartan medoxomil and 103.09 ± 1.259 for hydrochlorothiazide. Method validation was performed in accordance with USP guidelines.
Two stability-indicating chromatographic methods were developed for the analysis of dapsone in presence of its oxidative degradants. Forced degradation studies were performed on the drug substance using 30% hydrogen peroxide. The degradation products were identified by infrared spectroscopy and mass spectrometry, and a pathway is illustrated. The first method was based on thin-layer chromatographic separation of the drug from its oxidative degradants, followed by densitometric measurement of the intact drug spot at 289 nm. The developing system used for separation is ethyl acetate-toluene in the ratio 1:1 (v/v). The linear range was 0.5–6.0 μg/spot, with mean recoveries of 99.37 ± 0.96%. The second method was based on reversed-phase liquid chromatographic separation of the drug from its oxidative degradants on a C18 column, using the mobile phase methanol-water (65:35, v/v) at the controlled temperature of 25°C. Quantification was achieved by UV detection at 289 nm, based on peak area. The linear range was 5–65 μg mL−1 with mean recoveries 99.50 ± 1.70%. The methods were validated according to guidelines of International Conference on Harmonization. The HPLC method was used to investigate the kinetics of oxidative degradants at different temperatures.
New stability-indicating thin-layer chromatography (TLC)‒densitometry and reversed-phase liquid chromatography (RP-LC) methods for the determination of dabigatran etexilate mesylate (DEM) in the presence of its risky degradation products were developed and validated. The first method was a simple economic TLC‒densitometric method, where separation was achieved on aluminum plates pre-coated with silica gel gel 60 F254 using methanol‒ethyl acetate‒benzene (15:20:20, v/v) as the mobile phase. The method gave a compact and well-resolved spot for DEM. Quantification was performed at 225 nm over a concentration range of 0.3–3 μg per spot with a mean percentage recovery of 98.93 ± 0.80. The second method was an RP-LC method. Short analysis time and good efficacy were achieved on a BetaSil C 18 (4.6 mm × 250 mm, 5 μm) column using gradient elution. The flow rate was 1.5 mL min−1, and ultraviolet (UV) detection was carried out at 310 and 225 nm using time programming. The responses were linear over a concentration range of 5–100 μg mL−1 with a mean percentage recovery of 99.25 ± 0.74. The limit of quantification and limit of detection were 0.10 and 0.03 μg per spot for the TLC and 0.287 and 0.086 μg mL−1 for the LC method. The proposed methods were used for the identification and quantitative determination of DEM in bulk powder, pharmaceutical dosage forms, and in the presence of degradation products. The International Conference on Harmonization (ICH) guidelines were applied for validation of the methods.
A selective and economic high-performance thin-layer chromatography (HPTLC) method has been developed for the simultaneous determination of the co-administrated drugs, namely, granisetron, aprepitant, and deflazacort, used with chemotherapy. Granisetron, aprepitant, and deflazacort were chromatographed on HPTLC silica gel 60 F254 plates using chloroform‒methanol‒formic acid (18:1.5:1, v/v) as the developing system at R F values of 0.12 ± 0.06, 0.45 ± 0.02, and 0.58 ± 0.05, respectively. Densitometric measurements were carried out using a CAMAG TLC Scanner 3 at 220 nm. The cited method was applied for the analysis of granisetron, aprepitant, and deflazacort in a binomial relationship over a concentration range of 0.1–2, 0.2–4, and 0.1–2 μg per band, respectively. The limits of detection were found to be 0.027 μg per band for granisetron, 0.048 μg per band for aprepitant, and 0.031 μg per band for deflazacort. Method validation as per the International Conference on Harmonization (ICH) guidelines demonstrated the selectivity, sensitivity, accuracy, precision, and robustness of the method. The developed HPTLC method was found to be applicable to the dosage forms of the selected drugs with good recoveries and thus can be used for routine analysis in quality control laboratories. The cited HPTLC method was successfully applied for the detection and determination of the selected drugs in spiked plasma by liquid–liquid extraction using a mixture of dichloromethane and tert-butyl methyl ether (4:1, v/v). Moreover, statistical analysis of the results was performed revealing accuracy and precision.
Abstract
Samples of a new inorganic ion exchanger cerium(IV) molybdophosphate have been prepared under varying conditions. Ion exchange capacity, I.R, thermogravimetry and sorption of radionuclides have been studied. Separations of Sr−Rb and Cd−Ag have been developed on column of this ion exchanger.
Abstract
Iodine, thallium and uranium were determined by photon activation analysis. Two electron linear accelerators were used for the analysis of several kinds of environmental, biological and geochemical reference materials under different irradiation conditions. Both analytical results for iodine were in good agreement with each other but not with literature values in the case of environmental samples. The results of thallium and uranium agreed well with their reference values. The detectable concentration levels of iodine, thallium and uranium were almost 0.3μg/g.
