Practical Considerations When Using Fiber Optics for Dissolution Testing

Introduction The UV fiber optics system has emerged in dissolution testing of solid dosage forms as a useful alternative to conventional dissolution tests in both research & development and quality control. The system allows continuous in situ analysis of the drug concentration without the need for sample withdrawal and preparation. Therefore, this technique not only facilitates automation, but also eliminates potential errors in sample preparation. However, the fiber optic analysis itself possesses some sources of error. Several critical parameters, such as interferences with insoluble excipients and changes in hydrodynamics in the dissolution vessel with probe position have been thoroughly addressed by C. Schatz et al. [1]. In the first part of this study, the influence of the orientation of one-sided immersion probes (see figure 1) in the vessel was investigated. Stronger light scattering interferences on the dissolution results could be expected when the open side of the probe faces the flow direction, because the likelihood of insoluble excipients flowing into the light pathway is greater. In the second part of this study, interferences from air bubbles adhering to the immersion probe were evaluated. Without media deaeration, air bubbles might be formed during a dissolution test or while dipping the probe in the media. A prednisolone 5-mg tablet formulation with a low drug to excipient ratio (drug content <4% m/m) was chosen for these studies.