DETERMINATION OF RESIDENCE-TIME DISTRIBUTION IN IV TUBING OF IN-LINE DRUG DELIVERY SYSTEM USING DECONVOLUTION TECHNIQUE

The axial dispersion model was used in this work to describe the residence-time distribution (RTD) of solute molecules traveling along the i.v. tubing of an in-line drug delivery system. The degree of dispersion in this model was assessed by the magnitude of the dispersion coefficient, DBAR. In order to determine DBAR, a dilute sodium chloride solution was used as the tracer and infused at the beginning of the tubing for a short period of time. This method is termed the finite-pulse change. The elution profiles of sodium chloride at various flow rates were assayed at the entrance and the outlet of the tubing. A numerical deconvolution technique incorporated with Powell's nonlinear least-squares algorithm was then employed as the mathematical tool to search for the values of DBAR that give a best fit to these profiles. The results of modeling showed that the axial dispersion model gave an excellent fit to the experimental data. It was also observed that the plot of the obtained dispersion coefficient DBAR vs U, the mean fluid velocity in the tubing, was linear with a high degree of correlation. The results obtained in this work provide important information for optimization of in-line drug delivery kinetics.