Engelhard titanium silicate, ETS-4, is a promising new adsorbent for size-selective separation of mixtures of small gases, a leading industrially important example of which is methane-nitrogen separation. Single component equilibrium and kinetics of oxygen, nitrogen, and methane adsorption in Na-ETS-4 and cation-exchanged Sr-ETS-4, measured in an earlier study over a wide range of temperatures and pressures, are analyzed in this study. The adsorbent crystals were synthesized and pelletized under pressure (without any binder), thus giving rise to a bidispersed pore structure with controlling resistance in the micropores. Change in equilibrium and kinetics of adsorption of the aforementioned gases in Sr-ETS-4 due to pore shrinkage with progressively increasing dehydration temperature has also been investigated. Differential uptakes have been measured at various levels of adsorbate loading, which has allowed the elucidation of the nature of concentration dependence of micropore diffusivity. Both homogeneous and heterogeneous models are examined on the equilibrium data, while a bidispersed pore diffusion model is able to capture the differential uptakes very well. On the basis of chemical potential gradient as the driving force for diffusion, the impact of isotherm models on the concentration dependence of micropore diffusivity is also analyzed. It is shown that pore tailoring at the molecular scale by dehydration can improve the kinetic selectivity of nitrogen over methane in Sr-ETS-4 to a promising level. The models investigated are evaluated to identify essential details necessary to reliably simulate a methane-nitrogen separation process using the promising new Sr-ETS-4 adsorbent.

Strontium-exchanged titanium silicate, Sr-ETS-4, is a new molecular sieve with promises for exciting applications in gas separation. The literature mentions poor thermal stability and low adsorption capacity as the drawbacks of the as-synthesized Na-ETS-4 and therefore the need for cation exchange. Upon ion exchange, Sr-ETS-4 shows appreciable kinetic selectivity between methane and nitrogen, which can be improved further by controlled dehydration. In this study, we trace the changes at the molecular level behind this improvement. By combining distributed information in the literature, it is shown that the governing factors are changes in pore geometry with progressive dehydration, changes in ion occupancy, and relocation of cations due to Sr exchange.

The aim of current study was to develop and validate UV Spectrophotometric method for Fluconazole. Ultra Violet Spectroscopy was carried out at 260nm and samples were prepared with a solution of phosphate buffer pH 7.4. The linearity demonstrated a correlation coefficient of 0.998. The method was subjected to validity for the parameters as per ICH guidelines. Correctness, exactness, LOD, LOQ, recovery study and range were determined and the parameters were determined by performing the repeated experiments and proper sampling of the solution. The objective of selection of UV spectroscopy was the simplicity, time and economy of the method furthermore the sensitivity was also high by UV spectroscopy as HPLC technique is costly, time consuming and number of factors may affect the determination. It was observed that, the proposed method was linear, correct, repeatable, error free, selective, specific and cost effective proving the dependability of the method. More over same solvent was used throughout the experimental work and it was found that the method was free from any type of interference from any excipients and method was simple, rapid, precise, accurate and sensitive and can be applied in routine analysis of Fluconazole in single and combined form.