Theory and practice of pharmacopoeial control of the quality of drugs and excipients VII. The colour reference solutions of the European pharmacopoeia (Ph. Eur.)

Data calculations of three different workplaces consistently show that the difference in colour ΔE (CIELAB) of some colour reference solutions according to Ph. Eur. with small colour and purified water are too small. As a result, there is failure with use of these solutions for visual assessment of the coloration of the liquids. Solving the problem in Ph. Eur. presupposes the introduction of instrumental colour evaluation into this pharmacopoeia. Key words: Ph. Eur. • colour reference solutions • colour difference • CIELAB • visual assessment • instrumental measurement.