A Validated Densitometric Method for Analysis of Atorvastatin Calcium and Metoprolol Tartarate as Bulk Drugs and In Combined Capsule Dosage Forms

A simple, accurate and precise high-performance thin-layer chromatographic method has been developed for the estimation of Atorvastatin Calcium and Metoprolol Tartarate simultaneously from a capsule dosage form. The method employed Silica gel 60F 254sprecoated plates as stationary phase and a mixture of Chloroform: Methanol: Glacial acetic acid (dil.) :: (9:1.5:0.2 ml %v/v) as mobile phase. Densitometric scanning was performed at 220 nm using Camag TLC scanner 3. The method was linear in the drug concentrations’ range of 500 to 2500 ng/spot for Atorvastatin Calcium, also for Metoprolol Tartarate with correlation coefficient of 0.984 for Atorvastatin Calcium and 0.995 for Metoprolol Tartarate respectively. The retention factor for Atorvastatin Calcium was 0.45 ± 0.04 and for Metoprolol Tartarate was 0.25 ± 0.02. The method was validated as per ICH (International Conference on Harmonisation) Guidelines, proving its utility in estimation of Atorvastatin Calcium and Metoprolol Tartarate in combined dosage form

Design of catalytic membrane reactor for oxidatuive coupling of methane

Only abstract availabl

Development of an autothermal catalytic membrane reactor for the combination of the exothermic oxidative coupling and steam reforming of methane: a numerical study

A novel catalytic membrane reactor for the integration of the exothermic oxidative coupling (OCM) and endothermic steam reforming of methane (SRM) is proposed. A numerical model for the hollow fiber membrane with different catalytic activity on both sides has been developed and validated. It is shown how mass transfer limitations in the porous membrane layer can be effectively used to influence the ratio of OCM and SRM reaction rates and achieve autothermal operation. The intraparticle temperature gradients and bulk gas phase composition are quantitatively investigated, resulting in the formulation criteria required for the design of a hollow fiber catalytic membrane reactor

Integrated autothermal; oxidative coupling and steam reforming of methane. Part 2 : Development of apacked bed membrane reactor with a dual function catalyst

A numerical feasability study was performed on the integral performance of dual function catalyst particles in a packed bed reactor equipped with a porous membrane for distributive feeding of oxygen. The exothermic oxidative coupling and the endothermic steam reforming of methane (for simultaneous production of ethylene and synthesis gas) are integrated at the level of a porous catalyst particle with distributed activity, where the presence of the intraparticle heat-sink strongly reduces the total reaction heat and the temperature gradients in the reactor, eliminating the need for expensive conventional cooling of the reactor. Numerical simulations, with reaction kinetics taken from the literature, revealed that with distributive oxygen feeding via membranes indeed the local oxygen concentration in the packed bed membrane reactor can be kept low, which combined with a high Thiele modulus for oxidative coupling makes dual function catalysis possible. Using a reforming core diameter of approximately 15-40 micrometer, the steam reforming and oxidative coupling reaction rates could be effectively tuned to achieve autothermal operation, while the methane conversion was enhanced from 34 to 48% at optimum C2 production rates. In addition, it was shown that the temperature profiles in the reactor can be strongly reduced by employing the dual function catalyst and that the use of axial oxygen membrane flux profiles enables the use of a singele particle configuration to approach autothermal operation in the entire reactor

Integrated autothermal oxidative coupling and steam reforming of methane. Part 1 : Design of a dual-function catalyst particle

A dual-function catalyst particle which integrates the exothermic oxidative coupling and endothermic steam reforming of methane for the simultaneous autothermal production of ethylene and synthesis gas has been designed and studied by detailed numerical simulations. Compared to conventional oxidative coupling of methane, the introduction of a catalytic reforming activity signifantly increases the methane conversion without deteriorating the productivity towards the desired ethylene and ethane. Moreover, the presence of an intra-particle heat sink enables local autothermal operation, opening the possibility to couple these reactions in a packed bed membrane reactor with improved product yield. It is proposed to use a catalyst particle in which the two processes are physically separated by an inert, porous layer, such that additional diffusional resistances are intentionally created. The reforming activity is located in the particle center, while the oxidative coupling catalyst is present only in the outer shell of the particle. It has been demonstrated by means of numerical simulations that at a low oxygen concentration (representing conditions in a packed bed membrane reactor), the internal mass transfer limitations can be effectively utilized to regulate the total reforming reaction rates and prevent oxygen from reaching the reforming catalyst. Additionally, the size of the refoming catalytic core can, together with the effective diffusion properties inside the particle (viz. particle porosity and tortuosity) and the bulk gas phase concentrations, be used to tune the process to local autothermal operation

Integrated autothermal oxidative coupling and steam reforming of methane. Part 1 : Design of a dual-function catalyst particle

A dual-function catalyst particle which integrates the exothermic oxidative coupling and endothermic steam reforming of methane for the simultaneous autothermal production of ethylene and synthesis gas has been designed and studied by detailed numerical simulations. Compared to conventional oxidative coupling of methane, the introduction of a catalytic reforming activity signifantly increases the methane conversion without deteriorating the productivity towards the desired ethylene and ethane. Moreover, the presence of an intra-particle heat sink enables local autothermal operation, opening the possibility to couple these reactions in a packed bed membrane reactor with improved product yield. It is proposed to use a catalyst particle in which the two processes are physically separated by an inert, porous layer, such that additional diffusional resistances are intentionally created. The reforming activity is located in the particle center, while the oxidative coupling catalyst is present only in the outer shell of the particle. It has been demonstrated by means of numerical simulations that at a low oxygen concentration (representing conditions in a packed bed membrane reactor), the internal mass transfer limitations can be effectively utilized to regulate the total reforming reaction rates and prevent oxygen from reaching the reforming catalyst. Additionally, the size of the refoming catalytic core can, together with the effective diffusion properties inside the particle (viz. particle porosity and tortuosity) and the bulk gas phase concentrations, be used to tune the process to local autothermal operation

QM calculations predict the energetics and infrared spectra of transient glutamine isomers in LOV photoreceptors

© the Owner Societies 2021.Photosensory receptors containing the flavin-binding light-oxygen-voltage (LOV) domain are modular proteins that fulfil a variety of biological functions ranging from gene expression to phototropism. The LOV photocycle is initiated by blue-light and involves a cascade of intermediate species, including an electronically excited triplet state, that leads to covalent bond formation between the flavin mononucleotide (FMN) chromophore and a nearby cysteine residue. Subsequent conformational changes in the polypeptide chain arise due to the remodelling of the hydrogen bond network in the cofactor binding pocket, whereby a conserved glutamine residue plays a key role in coupling FMN photochemistry with LOV photobiology. Although the dark-to-light transition of LOV photosensors has been previously addressed by spectroscopy and computational approaches, the mechanistic basis of the underlying reactions is still not well understood. Here we present a detailed computational study of three distinct LOV domains: EL222 fromErythrobacter litoralis, AsLOV2 from the second LOV domain ofAvena sativaphototropin 1, and RsLOV fromRhodobacter sphaeroidesLOV protein. Extended protein-chromophore models containing all known crucial residues involved in the initial steps (femtosecond-to-microsecond) of the photocycle were employed. Energies and rotational barriers were calculated for possible rotamers and tautomers of the critical glutamine side chain, which allowed us to postulate the most energetically favoured glutamine orientation for each LOV domain along the assumed reaction path. In turn, for each evolving species, infrared difference spectra were constructed and compared to experimental EL222 and AsLOV2 transient infrared spectra, the former from original work presented here and the latter from the literature. The good agreement between theory and experiment permitted the assignment of the majority of observed bands, notably the ∼1635 cm−1transient of the adduct state to the carbonyl of the glutamine side chain after rotation. Moreover, both the energetic and spectroscopic approaches converge in suggesting a facile glutamine flip at the adduct intermediate for EL222 and more so for AsLOV2, while for RsLOV the glutamine keeps its initial configuration. Additionally, the computed infrared shifts of the glutamine and interacting residues could guide experimental research addressing early events of signal transduction in LOV proteins