In-Situ Dissolution Testing Using Different UV Fiber Optic Probes and Instruments

Introduction: Fiber optic technology for dissolution testing has been a topic of interest for many researchers for some years. Josefson, Johansson, and Tortensson 1 published early research in this field in 1988. They explored the feasibility of using UV fiber optics for in-situ dissolution and to overcome sample turbidity interference without filtration. In 1993, Brown and Lin 2 used a single optical fiber and a photo diode array (PDA) UV/vis spectrometer to track dissolution in a single vessel. Their work was extended thereafter to use six optical fibers and a PDA spectrometer for multiple dissolution vessels 3. In 1995, Cho and coworkers developed a sevenchannel fiber optic dissolution system using a spectrometer with two-dimensional chargecoupled devices (CCD), which allowed the simultaneous monitoring of six dissolution vessels and a seventh reference vessel 4,5. Several other studies around the same time further explored the possibility of using fiber optic technology for special dissolution applications. For example, Chen and his group 6,7 employed a fiber optic based chemical sensor for continuous monitoring of in-situ dissolution. Gemperline et al 8 applied a CCD/fiber optic system for determining two-component dissolution profiles of a pharmaceutical product, which used a full-range spectral principal component regression methodology. Aldridge and coworkers 9 automated a single-probe fiber optic system that used a robot arm to move the probe from vessel to vessel for sequential testing. All these breakthrough studies had great impact on subsequent development of commercial instruments and established the platform for modern in-situ fiber optic dissolution testing. Commercial UV fiber optic dissolution instruments became available in 1999. Several manufacturers in the United States introduced their independently developed instruments one after another. These commercial instruments employed either a spectrometer with multi-channel CCDs 10, 11, multiple PDA spectrometers 12,13, or a scanning spectrometer with a mechanical multiplexer 14,15. Commercialization of this technology and its consequent availability to a broad range of users has attracted much attention from the pharmaceutical industry. Recent publications and research works further described the capability of this technology 16-18 and demonstrated that UV fiber optics is a breakthrough for dissolution testing. A regulatory perspective on this technology has also been discussed in a recent article 19.