Size based separation of submicron nonmagnetic particles through magnetophoresis in structured obstacle arrays

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.The focus of this work was on developing a novel scalable size based separation technology for nonmagnetic particles in the submicron size range utilizing magnetophoretic forces. When a nonmagnetic particle is immersed in a magnetic fluid and subjected to magnetic field gradients, it behaves like a magnetic hole and experiences magnetic buoyancy forces proportional to its volume. This size dependence of magnetic buoyancy forces can be exploited to selectively focus larger nonmagnetic particles from a mixture and thus we can fractionate nonmagnetic particles on the basis of size. We designed a separation system composed of a regular array of iron obstacle posts which utilized magnetic buoyancy forces to perform size based separations. A Lagrangian particle tracking model was developed which could describe the behavior of a nonmagnetic particle in regions of inhomogeneous magnetic field gradients. Particle trajectories were simulated for a number of obstacle array geometries and over a range of operating conditions in order to understand the nature of the magnetic buoyancy force and aid in separation system design. Based on the results of the trajectory simulations, an experimental set up was conceptualized and built to demonstrate capture and separation of nonmagnetic particles using magnetic buoyancy forces. Capture visualization experiments were performed utilizing fluorescence microscopy which showed visual evidence of focusing and preferential capture of larger nonmagnetic particles. Experiments also yielded results qualitatively consistent with the Lagrangian trajectory model. Pulse chromatography experiments were also performed in order to quantitatively understand the capture and separation behavior. The results obtained showed quantitative evidence of preferential capture of larger particles. Particle capture efficiencies were compared with predictions from simulations and were found to be qualitatively consistent. Finally, the potential of this separation technology was demonstrated by performing proof-of-concept separation experiments with a mixture of 840 nm and 240 nm particles.by V. N. Ravikanth Annavarapu.Ph.D

PHARMACOKINETIC INVESTIGATION OF REMOGLIFLOZIN IN RAT PLASMA SAMPLES BY HIGH-THROUGHPUT HPLC-MS-MS

Objective: Remogliflozin (REMO), a selective inhibitor of the renal sodium-dependent glucose transporter 2 channel, which could increase urine glucose excretion and lower plasma glucose in humans. To establish a simple, sensitive and completely validated HPLC-MS-MS approach for the analysis of Remogliflozin in rat plasma samples. Methods: The method was developed after simple step protein precipitation by acetonitrile and Empagliflozin (EMPA) was used as internal standard. Separation was done on an CORTECS C18, 90 Å, 2.7 µm, 4.6 mm X 150 mm with an isocratic mobile phase consisting of 0.1% Formic acid: acetonitrile (20:80%, v/v) and pumped at a flow stream of 0.8 ml/min at ambient temperature. Results: The approach developed showed fine calibration curve in the quantity range of 5-1000 pg/ml with correlation coefficient (r2) of ≥ 0.9997 and the intra-run accuracy and precision was 99.91 to 109.07% and 0.17 to 1.34, inter-run accuracy and precision was 99.8 to 101.54 and 0.17 to 1.66 according to FDA guidelines. Conclusion: The newly designed and validated approach was simple, fast and applied effectively for single-dose oral pharmacokinetic investigation in Wistar male rats for the quantification of REMO in biological matrix