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  • Author or Editor: G. Shah x
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Abstract  

A novel method for the determination of palladium in synthetic nuclear waste samples has been developed using a computerized voltammetric analyzer. The electrode system consists of hanging mercury drop electrode (HMDE)/glassy carbon/Ag-AgCl electrode. Various experimental conditions including electrolyte type, pH and concentration have been optimized, leading to a detection limit of 40 ng/ml. The mixture of 4.10-3M citric acid + 2.10-2M ammonia-ammonium chloride buffer + 4.10-3M EDTA was used as a supporting electrolyte at pH 9.0. Standard addition method was employed to determine the concentration of palladium present in the nuclear waste sample. The relative standard deviation of the proposed method was found to be 8% at 40 ng/ml of palladium content. The method is direct, simple, rapid and free from any possible interference.

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Summary  

A method for solvent extraction, separation and recovery of uranium was developed using a new reagent, N-phenylbenzo-18-crown-6-hydroxamic (PBCHA) in the presence of cerium, thorium and lanthanides. Uranium was extracted with a dichloromethane solution of PBCHA producing an orange coloured complex at l max = 400 nm with a molar absorptivity of 5.0 . 104 l . mol-1 . cm-1 and which obeyed Beer's Law in the range of 0.48-5.76 ppm. For ICP-AES the extract was directly introduced into the plasma to enhance the sensitivity several folds with a detection limit of 0.5 ppb. The extraction constants of uranium crown hydroxamic acid complexes were also determined. The selectivity factors K uranyl(b 2 K/K or b 2 K'e/K) for uranium crown hydroxamate were evaluated by comparing the K uranyl with the stability constants of competing metal cations (K) and anions (K) and were found remarkably large. Uranium was recovered in 99.95% purity from monazite sand and phosphate rocks. It could be also preconcentrated and determined in environmental samples.

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A sensitive, specific, and accurate stability-indicating high-performance thin-layer chromatographic method for the analysis of ambroxol hydrochloride and doxofylline, for both bulk drug and formulation, was developed and validated according to the International Conference on Harmonization (ICH) guidelines. The densitometric analysis of both drugs was carried out in the absorbance mode at 276 nm using diethyl ether‒n-butanol‒ammonia (9:0.9:0.1, v/v) as the solvent system. This system was found to give compact spots for ambroxol hydrochloride at R F of 0.74 ± 0.01 and doxofylline at 0.41 ± 0.01. Moreover, both drugs were subjected to acid and alkali hydrolysis, oxidation, and photodegradation. Also, the degraded products were well resolved from the pure drug with different R F values. Linearity was found in the range of 20–100 and 100–500 ng band−1 for ambroxol hydrochloride and doxofylline. The limit of detection (LOD) and limit of quantitation (LOQ) for ambroxol hydrochloride and doxofylline were 1.17 and 3.57 ng band−1 and 30.68 and 92.97 ng band−1, respectively. “Bartlett’s test” and “Lack of fit” applied on peak area for linearity additionally proved validity of the linearity of the developed method. Good accuracy and precision were obtained as revealed from percent relative standard deviation (% RSD) less than 2. Moreover, robustness testing was performed applying fractional factorial design, 24–1. All the four factors: volume of diethyl ether, volume of n-butanol, solvent front, and chamber saturation time, evaluated in the robustness testing, were found to have an insignificant effect on the retention factor. Similarly, no interference was observed from common excipients in tablet formulation as well as degradation product, indicating specificity of the method. As the method could effectively separate both drugs from their degradation products, it can be used as a stability-indicating method.

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Abstract  

PbO based phosphate glasses having composition 40P2O5�12Al2O3�6B2O3�9PbO�xNa2O�(33−x)K2O (x=0−33) [F=Na/(Na+K)] have been prepared using conventional melt quench technique. Density, morphology, thermal expansion coefficient (α) and glass transition temperature (T g) were studied as a function of Na/(Na+K) ratio. Formation of transparent, bubble free and clear glass was observed up to x=18 mol%. Density was found to vary from 2.70 to 3.69 g cm−3. The significant changes were noticed in external morphologies at temperatures corresponding to softening, half ball and melting points under high temperature microscope for three compositions (x=0, 10 and 15 mol%). These glasses recorded the softening and half ball temperatures in the range 454–470�C and 523–576�C respectively and melting temperatures agree well with DTA studies within the experimental limits. Glass transition temperature showed a broad maxima while thermal expansion coefficient (TEC) a broad minima around Na/(Na+K)=0.54. This behaviour is explained on the basis of bond formation/phase separation.

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Two simple, accurate, specific, and precise chromatographic methods, reversed phase high-performance liquid chromatography (RP-HPLC) and highperformance thin-layer chromatography (HPTLC), have been developed and validated for the determination of moxifloxacin hydrochloride and difluprednate in ophthalmic dosage form according to International Conference on Harmonization (ICH) guidelines. The separation of moxifloxacin hydrochloride and difluprednate in HPLC was performed on reverse phase (C18, 5 μm, 250 × 4.6 mm) column using isocratic condition, with acetonitrile, 5 mM disodium hydrogen phosphate buffer adjusted to pH 5, and methanol (50:25:25, v/v/v) as mobile phase. The flow rate for analysis was 1.0 mL min−1, and the selected chromatographic conditions effectively separated moxifloxacin hydrochloride and difluprednate with retention time of 3.6 and 6.6 min, respectively, at a detection wavelength of 254 nm. Chromatographic development in HPTLC was performed on precoated silica gel 60F254 aluminium plates with n-hexane, 6 M ammonia, and acetone (5:1.8:2, v/v/v) as mobile phase. The detection wavelength for simultaneous estimation of both drugs was 232 nm in HPTLC, and the Rf values for moxifloxacin hydrochloride and difluprednate were 2.2 and 7.1, respectively. The linear concentration range for HPLC method was 5 to 50 μg mL−1 and 1 to 10 μg mL−1; and for HPTLC method was 1200 to 2200 ng band−1 and 200 to 1200 ng band−1 for moxifloxacin hydrochloride and difluprednate, respectively. Moreover, Bartlett's test applied on the calibration peak areas revealed homoscedasticity of variance for both the methods. Both methods were validated with respect to system suitability, specificity, linearity, precision, accuracy, and robustness. The mean percentage recoveries for marketed formulation in terms of accuracy were found to be 100.53 and 100.58 for HPLC; and 100.56 and 100.30 for HPTLC for moxifloxacin hydrochloride and difluprednate, respectively. The pooled percent relative standard deviation (% RSD) value for repeatability, intermediate precision, accuracy, and robustness studies for both the methods were found to be less than 2. Result of paired t-test at 95% confidence level reveals that there is no significant difference between recoveries of drugs, using both methods. The results of the developed chromatographic methods were acceptable assuring that these methods can be successfully applied for routine quality control testing of both bulk and ophthalmic dosage forms, without any interference from the excipients.

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