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Abstract  

The combination of lipophilic macrocyclic oxygen donors with the extractant thenoyltrifluoroacetone /HTTA/ has been shown to have a significant synergistic effect on the extractions of trivalent actinides and lanthanides. The results show that the nitrogen containing cryptand /222BB/ is a more effective synergist than the crown ether compound /15-C-5/ with only oxygen donors.

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Abstract  

Differential thermal analysis (DTA) of low-rank coals of high lignite to subbituminous rank from coal mines of Pakistan is reported. The studies carried out in dynamic oxygen atmosphere indicate that the exothermic reactions occur between 300 and 650°C and that the samples undergo stepwise oxidation of the organic matter rather than a continuous process as indicated by the pattern of shoulders from 250 to 350°C accompanying the main peak around 450°C. The effect of heating rate, particle size and volatile content was also studied in relation to oxidation. The results show that the increase in heating rate from 10 to 80 deg min−1 results in a marked shift in all the events in the DTA curve towards higher temperatures. As for the effect of particle size, the DTA records of 100–75, 150–100, 250–150 μm and greater than 250 μm fractions show that the magnitude and position of shoulder peaks are more sensitive to changes in particle sizes compared to the main peak. The curves recorded to study the effect of changing volatile content of samples between 30–40% indicate a complex pattern of shoulders accompanying the main peak. In general, the number of shoulder peaks increases with increasing volatile content of samples but their positions do not follow any trend. The DTA curves recorded in nitrogen contain ill-de-fined oxothermic effects over the 300–750°C temperature range. These curves consist of an endothermic peak around 150°C, two exothermic shoulders in the temperature region 300–400°C and a large broad exothermic whip between 500 and 700°C. The heating rates have similar effects as in oxygen while the particle size do not influence the results. It has been concluded that the organic matter in the coals studied here is extremely heterogeneous with different burning characteristics; as a result it is very difficult to quantify energy changes associated with poorly resolved exothermic events along the DTA curve. The effects also dominate in N2 atmosphere thus making identification of mineral matter difficult. The overall pattern of DTA events in oxygen can be correlated with the heating rate, particle size and volatile content of samples.

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Lipases are a class of enzymes which catalyze the hydrolysis of long-chain triglycerides. Microbial lipases are currently receiving much attention with the rapid development of enzyme technology. Bacillus subtilis FH5, isolated from tannery wastes, produced a thermostable alkalophilic lipase and was purified to homogeneity as judged by SDS-PAGE. The purification steps included acetone fractionation and sequential column chromatography on DEAE-cellulose, Sephadex G-75 and adsorption chromatography on Hydroxylapatite. The results of chromatographies showed that two types of lipases were present having molecular weights approximately 62 kDa and 24 kDa, respectively. The purified enzyme was found to be 100% stable at pH 10 and about 80% residual activity was present at 60°C. The enzyme was found to be stable in the presence of Mg 2+ , Mn 2+ and Ca 2+ ions. K m value was calculated as 5.05 mM and V max as 0.416 μmol/ml/min. Bacillus subtilis FH5 was isolated from tannery waste, therefore, enzyme is environmentally compatible for application in leather degreasing process.

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A new bacterial strain, capable of degrading poly(3-hydroxybutyrate) (PHB) was isolated from soil. This organism, identified as Streptoverticillium kashmirense AF1, secreted PHB depolymerases both on solid as well as in liquid mineral salt medium containing poly(3-hydroxybutyrate) as sole carbon source. The optimum production of PHB depolymerase was observed at pH 8 and 7, at 45 °C, 1% substrate concentration and in the presence of lactose as an additional carbon source. The extracellular PHB depolymerase was purified by gel permeation chromatography using Sephadex G-75. The Streptoverticillium kashmirense AF1 produced two types of PHB depolymerases having molecular weights of about 37 and 45 kDa as determined by SDS-PAGE. The difference in dry cell mass and amount of CO 2 evolved in the test and control calculated gravimetrically through Sturm test indicated the degradative capabilities of Streptoverticillium kashmirense AF1.

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Abstract  

A method has been developed for the radiassay of serum vitamin B12 using a competitive binding technique. By this method, vitamin B12 levels as low as 50 pg per ml of serum can be estimated in test samples. Egg yolk has been used as a test binding protein, which has several advantages over serum or plasma protein binding agents, as described in this paper. This binder is quite suitable and reliable for the assay of vitamin B12.

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Abstract  

The instrumental neutron activation analysis (INAA) of industrially important steel samples, viz. IS-226, IS-2002, IS-2062, SS-304, SS-310, SS-316 and of copper base alloys, viz. high brass, gun metal and copper-silver alloys is carried out with a 2 Ci252Cf neutron source. The copper and vanadium content of all the steel samples and manganese content of former three steel samples are estimated by measuring the gamma activity of66Cu,52V and56Mn radioisotopes, respectively, using a high purity germanium (HPGe) detector coupled to a 4 K multichannel analyzer (MCA). Similarly, the copper content of copper base alloys was also determined.

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A robust and eco-friendly stability-indicating high-performance thin-layer chromatography (HPTLC) method was developed for the stability study of thiocolchicoside using analytical quality-by-design approach. Full factorial design was used for screening potential variables affecting method development. Box‒Behnken design was used subsequently for investigation of the main, interactive, and quadratic effects of these variables on response. Four potential variables were selected on the basis of scientific knowledge for the development of a method for the stability study of thiocolchicoside. The selected potential factors, namely, volume of water (mL), saturation time (min), migration distance (mm), and volume of mobile phase (mL) were screened by 24 full factorial designs by selecting resolution as a critical method attribute. Pareto chart analysis showed that 3 variables, namely, volume of water (mL), saturation time (mm), and migration distance (mm), out of 4 potential variables were significantly affecting the response variable (resolution). Optimization with response surface methodology further clarified the relationship between critical variables and resolution using Box–Behnken design. The experimental design model was found to be quadratic, and the design space was developed on the basis of suggested model for optimization of critical method variables for maximum desirable resolution and for the development of a control strategy of the HPTLC method for the stability study of thiocolchicoside. The developed method was validated for linearity, range, specificity, precision, accuracy, limit of detection and limit of quantification as per the International Conference on Harmonization guidelines (ICH) Q2 (R1). The developed method was applied for the estimation of thiocolchicoside in its pharmaceutical dosage forms. The degradation products formed in acidic and alkaline media were isolated and characterized by their infrared (IR), nuclear magnetic resonance (NMR), and mass spectral data.

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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

An isocratic reversed-phase liquid chromatograpic assay method was developed for the quantitative determination of atorvastatin and aspirin (ASP) in combined dosage form. A Phenomenex Gemini C-18, 5-μm column with mobile phase containing 0.02 M potassium dihydrogen phosphate-acetonitrile-methanol (30:30:40, v/v/v) adjusted to pH 3 using o-phosphoric acid was used. The flow rate was 1.0 mL min−1 and effluents were monitored at 240 nm. The retention times (RTs) of atorvastatin calcium (ATV) and ASP were 10.5 and 3.8 min, respectively. ATV and ASP stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation, and dry heat degradation. The degraded product peaks were well resolved from the pure drug peak with significant difference in their RT values. Stressed samples were assayed using developed LC method. The proposed method was validated with respect to linearity, accuracy, precision, and robustness. The method was successfully applied to the estimation of ATV and ASP in combined capsule dosage forms.

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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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