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- Author or Editor: S. B. Kulkarni x
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A series of rare earth zeolites of types X and Y were prepared by cation exchange. Thermal analysis curves (TG/DTA) were employed to estimate the structural changes in the zeolite framework. Analogous investigations were carried out by independent methods such as XRD and IR spectroscopy. The results indicate increased thermal stability on the replacement of sodium by rare earth. Partial replacement of rare earth by ammonium/hydrogen enhances the thermal stability. The type Y zeolites are more stable than those of X type.
A derivatograph was used to follow the modification of the skeleton structure and thermal stability of zeolites in sodium and ammonium forms. Analogous investigations were carried out by independent methods such as IR and X-ray. Comparison showed good agreement between the results. The controlled dealumination of the Y-type zeolite enhanced the thermal stability
A systematic TG/DTG/DTA analysis is reported of anhydrous and heptahydrate forms of tris-phenanthroline and tris-pyridyl complexes of nickel(II), whose kinetic parameters were calculated by five different methods. The dehydration and de-ligation steps are descrete in Ni(phen)3Cl2 · 7 H2O, while those in Ni(bipy)3Cl2 · 7 H2O are mixed. Partial loss of the ligand is common for both hydrated and anhydrous compounds. In most cases the activation energyE a calculated from the mechanism-non-invoking equation of Horowitz and Metzger is in good agreement with that found from the mechanism-based relation of Mampel. There is an appreciable variation in magnitude in the results obtained from the different relations for the evaluation ofE a. It is inferred that such kinetic data are of significance in comparisons of the decomposition processes in related systems but not as absolute quantities.
The kinetics of oxidation of metallic fuels by metal oxides involve some of the most important parameters determining the utility of any metal oxide system in pyrotechnic applications. An attempt has been made to study the oxidation of Ta metal by strong oxidizers such as PbO2 and Pb3O4, employing differential thermal analysis and infrared spectroscopy. The rate of oxidation of Ta increases with increasing oxidizer content in both Ta-PbO2 and Ta-Pb3O4, systems. A tentative mechanism for the observed phenomenon is proposed.
Summary
Genotoxic impurities can be described as impurities that can induce genetic mutations and chromosomal breaks, or that damage the genetic information within a cell, which may lead to cancer. The European Medical Agency (EMA) and the United States Food and Drug Administration (US FDA) have set a threshold of toxicological concern (TTC) of genotoxic impurities 1.5 µg per day. In a continuous effort to develop an analytical method for the estimation of genotoxic impurities in quetiapine fumarate, a sensitive, simple, and precise high-performance thin-layer chromatography method has been developed and validated for the determination of 2-nitrophenyl (phenyl)sulfane as a genotoxic impurity at trace levels. The limits of detection (LOD) for quetiapine fumarate and 2-nitrophenyl (phenyl)sulfane were found to be 5.11 and 15.5 ng per band, whereas the limits of quantification (LOQ) were observed 0.09 and 0.3 ng per band, respectively. The calibration curve for 2-nitrophenyl (phenyl)sulfane was linear over the concentration range of 10 to 50 ng per band. The method was found to be specific, precise, linear, and accurate for the estimation of 2-nitrophenyl (phenyl)sulfane at trace levels in quetiapine fumarate.
A new, rapid, and specific reversed phase high-performance liquid chromatographic (RP-HPLC) method involving precolumn derivatization with benzoyl chloride was developed and validated for the estimation of γ-aminobutyric acid (GABA) in rat brain tissue preparations. The derivatization product of GABA was identified by melting point, infrared, and proton nuclear magnetic resonance (1H NMR) spectroscopy to be n-benzoyl GABA. Various parameters which influenced derivatization and elusion were optimized. The chromatographic system consisted of C-18 column with ultraviolet (UV)—photodiode array detection ranging from 210 to 400 nm. Elution with an isocratic mobile phase consisting of 0.025 M disodium hydrogen phosphate buffer—methanol (65:35, v/v; pH 6) at a flow rate of 1 mL min−1 yielded sharp and specific peak of n-benzoyl GABA within 7 min. The method was validated with respect to the linearity, accuracy, precision, sensitivity, selectivity, and stability, wherein the benzoyl derivative of GABA showed stability for 2 months. The lower limit of detection was 0.5 nmol L−1. This novel derivatization procedure for the estimation of GABA with benzoyl chloride was also applied for rat brain tissue preparations that gave highly specific peak and good component recovery. The results show that the method for the determination of GABA by benzoylation using RP-HPLC has good linearity, accuracy, precision, sensitivity, and specificity and is simple and economical to perform.
Summary
Genetic mutations, chromosomal breaks, and chromosomal rearrangements, which are induced due to organic impurities, are considered as potential genotoxic impurities. The European Medicines Agency (EMA) and the United States Food and Drug Administration (US FDA) have set a threshold of toxicological concern (TTC) of 1.5 µg per person per day for each impurity. A sensitive and simple high-performance thin-layer chromatography (HPTLC) method has been developed and validated for determination of the potential genotoxic impurity, namely, 2-chloroaniline, at trace levels in quetiapine fumarate. The method was found to be specific and selective for the application. The limit of detection (LOD) and limit of quantification (LOQ) for quetiapine fumarate were found to be 1.27 and 3.87 ng per band. The LOD and LOQ values for 2-chloroaniline were found 0.018 and 0.054 ng per band, respectively. The calibration curve for 2-chloroaniline was linear over a concentration range from 2.5 to 12.5 ng. The method was found to be specific, precise, linear, and accurate and can be employed for monitoring and estimation of levels of 2-chloroaniline in quetiapine fumarate.
Summary
2,4-Dichlorophenoxyacetic acid (2,4-D) is a phenoxy group of herbicide used worldwide. As it is extensively used, it has consequential problems on living beings. 2,4-D is degraded into the chlorinated phenols and catechols, and these phenol compounds are more hazardous than the parent 2,4-D herbicide. In this paper, an attempt is made to detect 2,4-dichlorophenol in 2,4-D poisoning cases from human viscera. Sensitive and selective detection of 2,4-dichlorophenol using high-performance thin-layer chromatography (HPTLC) is possible by coupling it with 4-amminoantipyrene in the presence of potassium ferricyanide. Standard 2,4-dichlorophenol and human visceral extract are allowed to run on an HPTLC plate with hexane, acetone, and ethyl acetate as the mobile phase. Mechanistically, 4-amminoantipyrene reacts with 2,4-dichlorophenol in the presence of potassium ferricyanide to form p-quinoneimide which is brick red in color. This known reaction is, for the first time, applied to detect 2,4-dichlorophenol in 2,4-D poisoning cases from human viscera. The formation of brick red color spot on the HPTLC plate allows the easy and confirmed detection of 2,4-dichlorophenol in 2,4-D poisoning case. This HPTLC method is simple and easy to work in laboratory. The reagents do not react with the parent 2,4-dichorophenoxyacetic acid and other organophosphorus, organochlorine, carbamate, and pyrethroid insecticides, i.e., these reagents are specific. The constituents of the viscera (amino acids, peptides, proteins, etc.) and plant material do not interfere with the reagents. The presence of 2,4-dichlorophenol in the same visceral sample is confirmed by gas chromatography-mass spectrometry (GC-MS). The detection limit of reagents for 2,4-dichlorophenol is approximately 0.5 µg.
