Determination of β-blockers in pharmaceutical and human urine by capillary electrophoresis with electrochemiluminescence detection and studies on the pharmacokinetics.
ABSTRACT A novel method for simultaneous determination of atenolol, metoprolol and esmolol was proposed by capillary electrophoresis (CE) separation and electrochemiluminescence (ECL) detection. Poly-β-cyclodextrin (Poly-β-CD) was used as an additive in the running buffer to improve the separation of three analytes. The conditions for CE separation, ECL detection and effect of Poly-β-CD were investigated in detail. The three β-blockers with very similar structures were well separated and detected under the optimum conditions. The linear ranges of the standard solution for atenolol and esmolol were 2.5-125 μmol/L with a detection limit (S/N=3) of 0.5 μmol/L, and for metoprolol was 0.5-25 μmol/L with a detection limit of 0.1 μmol/L. For three β-blockers from spiked aqueous and urine samples, the accuracy and precision including intraday and interday experiments were performed by calculating the recovery, the relative standard deviations of the ECL intensity and the migration time, respectively. The developed method was applied to the determination of metoprolol content in commercial pharmaceutical, and the analytical results are in good agreement with the nominal value with recoveries in the range of 98.7-105%. The proposed method was also applied to the monitoring of pharmacokinetics for metoprolol in human body.
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ABSTRACT: Desorption of oxygen and hydrogen from various liquids (water, 0.8 molar sodium sulphate solution) containing suspended particles of activated carbon at various solid loading was investigated. The desorption was used to avoid supersaturation effect which was observed during oxygen and hydrogen absorption into liquid saturated with nitrogen. Experiments were carried out in a stirred cell with flat gas–liquid interface at and atmospheric pressure. An increase of kL upon addition of the particles was observed. Enhancement factor increases with increasing contact time of the particles with liquid reaching maximum steady-state value of approx. 3 after sufficiently long time (a few hours) regardless of solid loading , agitator frequency and solute gas (O2,H2). The results fit the correlation (e is specific power dissipated by agitator in liquid and D is molecular diffusivity of gas absorbed) with the exponent for liquids without and for the liquids with the particles. It indicates that the interface is rigid in absence of particles and hinders the motion of liquid along the interface forming boundary layer while in the presence of particles the interface is completely mobile and surface renewal proceeds according to the penetration model. These results confirm a finding of Kaya and Schumpe (2005) that the enhancement of mass transfer in the cell at the presence of hydrophobic solids is due to clean-up of the interface from surfactants by their adsorption on hydrophobic solids rather than by a “shuttle mechanism” exerted by particles with a high adsorption capacity for the transfer component.Chemical Engineering Science. 01/2006;
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ABSTRACT: This paper investigates the reduction of ionic concentration and carbon oxygen demand (COD) in dairy process waters modelled by one volume of skim milk diluted with two volumes of water using shear-enhanced reverse osmosis. Initial COD and conductivity were, respectively, 36,000 mg O2 L−1 and 2000 μS cm−1. We have compared the performances of a VSEP vibratory pilot and of a single rotating disk-stationary membrane module equipped with the same Desal AG membrane (Osmonics). Membrane shear rates were varied by changing the vibration frequency in the VSEP and the disk rotation speed or adding radial vanes in the other module. In all tests the permeate COD was reduced below 15 mg O2 L−1. Permeate fluxes reached a maximum of 180 L h−1 m−2 at a transmembrane pressure (TMP) of 4 MPa at initial concentration with the VSEP at its resonant frequency and with the disk equipped with 6 mm high vanes rotating at 2000 rpm. Permeate conductivity fell from 60 μS cm−1 at 1 MPa to about 18 μS cm−1 at 4 MPa. In concentration tests, corresponding permeate fluxes at the maximum volume reduction ratio reached (VRR = 8), were 55 L h−1 m−2 for the VSEP and 60 L h−1 m−2 for the rotating disk at a TMP of 4 MPa. Permeate conductivities increased exponentially with VRR from 18 to 210 μS cm−1 for the rotating disk and to 250 μS cm−1 for the VSEP. However the mean conductivity of collected permeate varied from 38 μS cm−1at highest shear rate to 60 at lower shear rates. This study shows that these filtration systems permit to obtain reusable water from this high initial COD model effluent with one single reverse osmosis step.Separation and Purification Technology. 01/2008;
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ABSTRACT: In this paper, heat transfer characteristics of a liquid-solid fluidized bed with an immersion heater are experimentally investigated. Specifically, the axial dispersion coefficients of fluidized particles are measured by means of a relaxation method to examine the effects of particle motion on the rate of heat transfer. Furthermore, the effects of the liquid flow rate or bed porosity and of the particle size on the heat transfer resistance in the region adjacent to the heater surface and that in the bed proper are examined. The resultant data have been analyzed in terms of the two resistance-in-series model.AIChE Journal 06/2004; 37(7):1101 - 1106. · 2.49 Impact Factor