The Effect of Probe Path Length Calibration on Dissolution Tests Performed with a Fiber-Optic In Situ Dissolution Test System

Abstract

The purpose of this research was to provide a method for calibrating the path length of probes used for dissolution tests performed with a fiber-optic dissolution test system (FODT). Methods found in pharmacopeia use the absorptivity of a 60.0 µg/mL potassium dichromate solution for calibrating 10-mm cuvettes. This absorptivity should only be employed to calibrate probes with a 5-mm gap where the total path length is 10 mm, since the calibration will be inaccurate if this absorptivity is used with different path length probes. In this article, we establish a calibration method using the absorptivities of potassium dichromate solutions at concentrations of 120.0, 300.0, and 600.0 µg/mL with 5-, 2-, and 1-mm cuvettes to calibrate probes with 2.0-, 1.0-, and 0.5-mm gaps, respectively. The calibration method established here for FODT minimizes calibration inaccuracies observed with calibration of probes using the method in Appendix IVA of the Chinese Pharmacopeia.