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Abstract  

The present article describes the synthesis, structural features and thermal studies of heterochelates of the type [M(SB)(benen)(H2O)]·nH2O [where H2SB=(Z)-2-(2,2,2-trifluoro-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethylideneamino)benzoic acid, benen=bis(benzylidene)ethylenediamine and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and VO(IV)]. The Schiff base (H2SB) have been characterized on the basis of elemental analysis, IR, 1H and 13C NMR. The heterochelates have been characterized on the basis of elemental analyses, magnetic measurements, solid state conductivity measurements, IR, reflectance spectra, and thermal studies. The FAB mass spectrum of [Co(SB)(benen)(H2O)] has been carried out. The kinetic parameters such as order of reaction (n) and the energy of activation (E a) have been reported using Freeman-Carroll method. The pre-exponential factor (A), the activation entropy (ΔS #), the activation enthalpy (ΔH #) and the free energy of activation (ΔG #) have been calculated.

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Summary

A new, simple, accurate, and precise high-performance thin-layer chromatographic (HPTLC) method has been established for simultaneous analysis of eprosartan and hydrochlorothiazide in tablet formulations. Standard and sample solutions of eprosartan and hydrochlorothiazide were applied to precoated silica gel G 60 F254 HPTLC plates and the plates were developed with benzene-methanol-formic acid 7:3:0.1 (υ/υ) as mobile phase. Detection and evaluation of chromatograms was performed densitometrically at 272 nm. The retention factors of eprosartan and hydrochlorothiazide were 0.76 and 0.57, respectively. The linear range was 4.8–43.2 μg per spot for eprosartan and 0.15–1.35 μg per spot for hydrochlorothiazide; the correlation coefficients, r, were 0.998 and 0.999, respectively. The method was validated and successfully used for analysis of the drugs in tablets.

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Transition metal complexes with uninegative bidentate Schiff base

Synthetic, thermal, spectroscopic and coordination aspects

Journal of Thermal Analysis and Calorimetry
Authors: C. K. Modi, S. H. Patel, and M. N. Patel

Abstract

The present article describes the synthesis, structural features and thermal studies of the complexes of the type [M(SB)2(H2O)2nH2O [where HSB=pyridine-m-carboxaldene-o-aminobenzoic acid and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)]. The complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurements, (FTIR and electronic) spectra and thermal studies. The nature of the bonding has been discussed on the basis of infrared spectral data. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated structure of these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature.

The thermal decomposition of the complexes have been studied and indicates that not only the crystallization and coordinated water are lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass losses. The kinetic parameters such as order of reaction (n) and the energy of activation (E a) have been reported using Freeman–Carroll method. The entropy (S*), the pre-exponential factor (A), the enthalpy (H*) and the Gibbs free energy (G*) have been calculated.

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Summary

A rapid, selective, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay has been proposed for the determination of aripiprazole in human plasma. The analyte and propranolol as internal standard (IS) were extracted from 200 μL of human plasma via liquid-liquid extraction using methyl tert-butyl ether under alkaline conditions. The best chromatographic separation was achieved on an Aquasil C18 (100 × 2.1 mm, 5 μm) column using methanol-deionized water containing 2 mM ammonium trifluoroacetate and 0.02% formic acid (65:35, v/v) as the mobile phase under isocratic conditions. Detection of analyte and IS was done by tandem mass spectrometry, operating in positive ion and multiple reaction monitoring (MRM) acquisition mode. The method was fully validated for its selectivity, interference check, sensitivity, carryover check, linearity, precision and accuracy, reinjection reproducibility, recovery, matrix effect, ion suppression/enhancement, stability, ruggedness, and dilution integrity. The assay was linear over the concentration range of 0.10–100 ng mL−1 for aripiprazole. The intra-batch and inter-batch precision (%CV) was ≤4.8%, while the mean extraction recovery was >96% for aripiprazole across quality control levels. The method was successfully applied to a bioequivalence study of 10 mg aripiprazole orally disintegrating tablet formulation in 27 healthy Indian subjects under fasting and fed condition. The reproducibility in the measurement of study data was demonstrated by reanalysis of 260 incurred samples.

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In this research work comprehensive stress testing of irbesartan was carried out according to ICH guideline Q1A (R2), and a stability-indicating reversed-phase ultra-performance liquid chromatographic (UPLC) assay was established. The drug was subjected to acid (0.1 m HCl), neutral, and alkaline (0.1 m NaOH) hydrolytic conditions at 80°C, and to oxidative decomposition at room temperature. Photolysis was carried out by exposing the drug to sunlight (60,000–70,000 lux) for two days. The solid drug was also subjected to 50°C for 60 days in a hot-air oven. Degradation of the drug was found to occur under alkaline, acidic, and neutral hydrolytic conditions. Separation of the drug and the degradation products was successfully achieved on a BEH (bridged ethylene hybrid) C18 column with 40:60 aqueous glacial acetic acid (0.2%)-acetonitrile as mobile phase. The flow rate and detection wavelength were 0.1 mL min−1 and 229 nm, respectively. The method was validated and response was found to be linear in the drug concentration range 10–50 μg mL−1. The mean values (±RSD, %) of slope, intercept, and correlation coefficient were 32102 (± 0.0535), 1295 (± 3.02), and 0.9998 (± 0.0493), respectively. RSD in intra-day and inter-day precision studies was <1%. Recovery of the drug from a mixture of degradation products was between 99.26 and 100.01%. The method was specific to the drug, selective to degradation products, and robust. PDA purity test also confirmed the specificity of the method.

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The interaction between salinity (8 and 12 dS m −1 ) and three levels (40, 80 and 120 kg ha −1 ) of different forms of nitrogen (NO 3 , NH 4 + and NO 3 + NH 4 + ) were studied in Brassica juncea cv. RH-30. The plants were salinized with 8 and 12 dS m −1 at 35 and 55 days after sowing. The relative water content (RWC), water potential (Ψ w ) and osmotic potential (Ψ s ) exhibited a marked decline under salinity stress. The application of the combined form (NO 3 + NH 4 + ) of nitrogen (120 kg ha −1 ) considerably improved the water status and mitigated the adverse effect of salinity on growth. The salinity-induced osmotic effect led to stomatal closure and caused a substantial reduction in net photosynthetic rate (P N ), stomatal conductance (g s ) and transpiration rate (E) at the pre-flowering and flowering stages (45 and 65 DAS). Salinity effects were considerably moderated by additional nitrogen supply, which varied with the source of nitrogen, the level of salinity/fertilizer and the stage of plant growth. The inhibition in photosynthesis was relatively greater in ammonium-fed (NH 4 + ) than in nitrate-fed (NO 3 ) plants, while the transpiration rate was relatively lower in nitrate-fed plants grown either with or without saline water irrigation. The nitrate form of nitrogen @ 120 kg ha −1 proved best in alleviating the adverse effect of salinity on photosynthesis and transpiration at both the growth stages.

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Abstract  

In the present report, thermal analysis (TMDSC, DMA, TG, stress-strain analysis), nano-indentation and AFM morphological characterization of cross-linkable latexes, prepared with either a pre-coalescence cross-linker (1,3-butylene glycol dimethacrylate) or post-coalescence cross-linker (adipic dihydrazide) at various levels of cross-linking, were done. The study assesses the effect of type and level of cross-linking on the film formation process through the evolution of mechanical properties and latex morphology. In addition, the final fundamental thermal and mechanical properties, specific end-use properties and latex morphology resulting from the film formation process are reported.

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