Color measurement of a solid active pharmaceutical ingredient as an aid to identifying key process parameters.

The color of a powdered active pharmaceutical ingredient (API) in an investigational drug was found to be the result of a number of process parameters. Color measurements of the solid material were derived from reflectance data obtained from a sphere spectrophotometer. These data provided a convenient and non-destructive way to track the effects of variations to the process parameters on the resulting material. Visual evaluation could not provide an objective, quantitative assessment of the material. Color of solution (COS) measurements did not provide adequate sensitivity to distinguish some of the samples from each other, even when visual differences were apparent.