Effect of Tapped Density, Compacted Density, and Drug Concentration on Light-Induced Fluorescence Response as a Process Analytical Tool

The effect of tapped density, compacted density, and fluorescent drug concentration on the light-induced fluorescence (LIF) response is reported. The fluorescent response to powder mixtures containing 0.25%-10.00% w/w fluorescent active pharmaceutical ingredient (API) was evaluated over a density range of about 0.641-1.370 g/cm3. Blend concentrations up to 4.00% w/w API showed a linear trend in LIF response with increasing tapped and compacted density. API concentrations of 4.00% w/w or greater exhibited a negative parabolic trend in LIF response. The LIF responses were fitted to a quadratic model equation that included an interaction term between material density and API concentration (adjusted R2 = 0.975 and p < 0.0001). All model terms were highly significant, including the material density-API concentration interaction (p < 0.0001). Being aware of the sensitivity of the LIF response to material density changes and the related changes in apparent concentration are important in implementing LIF as a process analytical tool for processes such as blending, roller compaction, and tableting.