RESUMEN
Adsorption techniques are widely used to remove some classes of pollutants from waters, especially those which are not easily biodegradable. The removal of Methylene blue (MB), as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. The aim of this study is to eliminate MB by Activated Coconut Shells (ACS) produced at low cost by adsorption in batch mode. The ACS was characterized by the FTIR spectroscopy and point of zero charge (pHpzc: 5.06). Some examined factors were found to have significant impacts on the MB uptake of ACS like the initial dye concentration Co (40-120 mg/L), solution pH (2-8), ACS dose (1-12 g/L), agitation speed (50-500 r/min), particles size (1.0-1.2 mm) and temperature (298-333 K). The best capacity was found at pH 6 with an adsorbent dose 8 g/L, an agitation speed 200 r/min and a contact time of 60 min. Modeling Kinetics and Isotherms shows that the pseudo-second-order kinetic model with R 2 (0.935 -0.998) and Langmuir adsorption isotherm model provide better fitness to the experimental data with the maximum adsorption capacity of 30.30 mg/g at 25°C. The separation factor RL (0.933-0.541) in the concentration range studied (10-120 mg/L) shows a favorable adsorption. The isotherms at different temperatures have been used for the determination of the free energy ΔG° (198-9.72 kJ/mol); enthalpy ΔH° (82.082 kJ/mol) and entropy ΔSo (245.689 J/K mol) to predict the nature of MB adsorption process. The positive values of (ΔGo) and (ΔHo) indicate a non-spontaneous and endothermic MB adsorption with a chemisorption. The adsorbent elaborated from Coconut Shells was found to efficient and suitable for the removal of MB dye from aqueous solutions, due to its availability, low cost preparation and good uptake capacity.
RESUMEN
Antibiotics are widely used in veterinary and human medicine, but these compounds, when released into the aquatic environment, present potential risks to living organisms. In the present study, the activated carbon (AC) used for their removals is characterized by FT-IR spectroscopy, BET analysis and Scanning Electron Microscopy (SEM) to determine the physicochemical characteristics. Response surface methodology (RSM) and Box-Behnken statistical design (BBD) were used to optimize important parameters including pH (2-12), temperature (20-45°C), and AC dose (0.05-0.20 g). The experimental data were analyzed by analysis of variance (ANOVA) and fitted to second-order polynomial using multiple regression analysis. The optimal conditions for maximum elimination of Amoxicillin (Amox) are (Dose: 0.124 g, pH 5.03 and 45°C) by applying the desirability function (df). A confirmation experiment was carried out to evaluate the accuracy of the optimization model and maximum removal efficiency (R = 89.999%) was obtained under the optimized conditions. Several error analysis equations were used to measure goodness of fit. Pareto analysis suggests the importance of the relative order of factors: pH > Temperature > AC dose in optimized situations. The equilibrium adsorption data of Amox on Activated Carbone were analyzed by Freundlich, Elovich, Temkin and Langmuir models. The latter gave the best correlation with qmax capacities of 142.85 mg/g (R2 = 0.999) at 25°C is removed from solution. The adsorption process is dominated by chemisorption and the kinetic model obeys a pseudo-second order model (R2 = 0.999).
RESUMEN
Combination therapy has a pivotal role in type II diabetes mellitus management in patients unable to maintain normal glycemic level using metformin alone. Addition of linagliptin, dipeptidyl peptidase-IV inhibitor, to metformin improves glycemic control. This study is concerned with the development of an HPLC-MS/MS method for simultaneous quantification of linagliptin and metformin in spiked human plasma. The method was applied to evaluate the potential pharmacokinetic interactions between the cited drugs in healthy volunteers. Solid phase extraction was applied using Strata™ X cartridge. Separation was carried out on Symmetry® C18 column using methanol: 10 mM ammonium formate buffer (containing 0.2% formic acid) in a ratio of (95: 5, v/v) as mobile phase at flow rate 0.25 mL min-1. Quantification was performed with multiple reaction monitoring in positive ionization mode. The monitored transitions were set at m/z 473.24 â 419.94, 130.14 â 60.18 and 340.27 â 116.07 for linagliptin, metformin and alogliptin (internal standard), respectively. The method was validated according to FDA guidelines. The method showed excellent linearity over concentration ranges 0.25-10 and 25-2000 ng mL-1 for linagliptin and metformin, respectively. The validated HPLC-MS/MS method was successfully applied to pharmacokinetic study of linagliptin and metformin in healthy volunteers after oral administration of Jentadueto® tablets.