Etoricoxib selective sensor based on uracil-5,6-diamino-2-thio hydrochloride as neutral carrier for potentiometric analysis in pharmaceutical preparations
A construction and electrochemical behavior of novel potentiometric membrane sensor responsive to the etoricoxib was described. The sensor was based on the ion-pair complex of etoricoxib (ET) with Uracil-5,6-diamino-2-thio hydrochloride UDTH (ET-UDTH) as exchange sites in a PVC matrix with different plasticizers dibutylphthalate (DBP) (electrode B) tri-n-butylphosphate (TBP) (electrode C), and dioctylphthalate (DOP) (electrode A). The electrodes exhibited near-Nernstian response for ET-UDTH over the concentration range 0.051-40.042 mM. The electrode offered significant advantages including long lifetime (about 2 months), excellent stability and reproducibility, good response time (10-25 s), and wide pH working range (pH 5-12). Selectivity coefficients of ET related to a number of interfering cation and some organic compounds were investigated, and there were negligible interference caused by most of the investigated species. The direct determination of 0.5-10 mM of ET showed an average recovery of 99.03-101.75% and a mean relative standard deviation 0.40-1.88. The results were obtained by determination of ET in tablets using the proposed electrodes which were comparable favorably with those obtained by spectrophotometric method
PURE
Abstract Despite large public policy efforts over the past 30 years, a large minority of households remains consistently inadequately prepared for retirement. If policymakers want to address this shortcoming, public policy has to change from its current path. This paper suggests a system of mandatory private pensions funded by a minimum mandatory contribution of 3% of payroll. In addition, a number of institutional changes are suggested to reduce the costs and risks of individual accounts.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.