Purpose: To evaluate fluid flow profiles in the flow-through cell (FTC, USP apparatus 4) system with pulsatile and non-pulsatile pumps.
Methods: Instantaneous velocity vectors in the dissolution cells were obtained from images sequentially captured by a particle image velocimetry (PIV) system. The data were sorted to follow the pump pulse cycle.
Results: The analysis showed changes in the flow profiles during a pump pulse (0.5 s) at a 0.025-s interval in two sizes of cells installed in the FTC system. Supplying a slow flow from the pulsatile pump induced instantaneous downward (inner layer) and upward (outer layer) flow in the larger cell during the suction phase. Analysis at varied medium and cell temperatures strongly suggested a contribution of natural convection to the complex flow caused by relatively high cell temperature. Uniform upward flow was observed in other cells and flow rate conditions. The time-averaged vertical velocities in the cells were similar in the pulsatile and non-pulsatile pump systems.
Conclusions: The PIV analysis provides information on how flow rate and pump pulse affect fluid flow profiles at multiple points in flow-through dissolution cells. An appropriate temperature control should reduce the complex flow of the medium in the FTC system.