Study of drug distribution of granules with diffuse reflectance spectroscopy

The aim of this study was to quantitatively evaluate the intergranular migr ation of quinidine bisulphate using diffuse reflectance spectroscopy. Granu les containing different quantities of quinidine bisulphate (1-20% w/w) wer e prepared and tray-dried. After drying, the granules were fractionated int o seven horizontal layers. The quinidine bisulphate concentration of the di fferent layers was determined quantitatively using UV spectrophotometry and diffuse reflectance spectroscopy. A linear relationship was found, wit a g ood correlation between the quinidine bisulphate concentration of the granu le layers and their logarithm of reciprocal diffuse light reflectance (log l/R) at the characteristic wavelength of quinidine bisulphate (333 nm). The se results suggest that diffuse reflectance measurements could be applied t o investigating the in-process homogeneity of active substance in granule s amples, without the need for destructive sample preparation.