A precise colour determination method for tablets--an application of instrumental colour measurement in the pharmaceutical development.

ICH guideline Q6A requires a quantitative procedure to investigate changes in colour. For such purpose, it is necessary to conduct the instrumental colour measurement according to USP 28 <1061>. An adequate, precise, reproducible, and reliable equipment is introduced and the equipment qualification data presented. The colour of tablets coated with inorganic pigments like red and yellow ferric oxide, and white titanium dioxide shows the within-batch and batch-to-batch variabilities the extent of which is tested by CIELAB. Visual colour matching data reveal a considerable variability during the stability program while the mean CIELAB values do not vary. The visual matching should rather be replaced by the instrumental colour matching because the latter is free from the variabilities caused by human perception. The instrumental colour matching method is presented and proven to be reproducible, reliable and precise.