Technical evaluation of a fiber-optic probe dissolution system

A systematic investigation was performed on the Delphian Rainbow Dissolution Monitor (R) to fully characterize the analytical performance of this instrument. The spectra of more than thirty commonly used pharmaceutical excipient samples were analyzed and grouped into three categories based on their UV absorbance or scattering properties. Scattering interference from the insoluble excipients is unique to the UV fiber-optic in situ analysis, since all components are present during the analysis; therefore, it was further evaluated for its impact on accuracy, linearity, and precision. The simple baseline-correction algorithm worked well to minimize spectral interference derived from excipient scattering because of the fact that scattering is mostly wavelength independent for the excipients studied in this work. The baseline-corrected spectra demonstrated that the presence of insoluble excipients did not have significant impact on linearity or accuracy. However, increased variability in the presence of insoluble excipients led to an increase in the minimum measurable absorbance from 0.03 to 0.05 absorbance units (AU), which ultimately limits low-level quantitative measurements. Assessment of four different path lengths showed consistent linearity in the operational range of 0.05-1.5 AU. The linear range was observed to decrease at shorter wavelengths (240-nm cutoff) due to the lack of full transmittance, which is consistent with the specification defined by the manufacturer. In addition, practical recommendations are provided to allow the user to get the most accurate data from the system.