Measurement of surface color as an expedient QC method for the detection of deviations in tablet hardness

The objective of this study was to investigate whether a correlation exists between the surface color of tablets and their tensile strength. Theophylline powder blends with and without red dye were directly compressed into 600mg tablets. Applied compression pressure ranged from 9.3 to 271.2MPa. Colorimetric parameters: lightness (L), chromaticity (a, b), chroma (Cab), hue (hab) and color intensity (CI), were measured and recorded for both sides of each tablet using ColorQuest XE colorimeter in reflectance specular included mode. The tensile strength of the tablets was measured using a TA.XTPlus Texture Analyzer. A linear correlation was observed between the chroma (Cab) parameter and the tensile strength for each formulation of the tablets. For white tablets, the linearity was observed between Cab values ranging from 2.6 to 3.76 and tensile strength values ranging from 2.96 to 6.86MPa. For red tablets, the linearity was observed between a chroma range from 21.76 to 30.75 and tensile strength from 2.51 to 6.52MPa. A similar correlation was observed between the CI of red tablets and tensile strength. It was concluded that chroma could be used as suitable QC parameters to detect deviations in tablet hardness during bulk manufacturing.