Study of the British Pharmacopeia method on methimazole (thiamazole) content in carbimazole tablets.

The analysis of carbimazole tablets in The British Pharmacopoeia, 1993, includes a quantitative thin layer chromatography (TLC) determination of methimazole. Repeated analysis of the same samples did not give similar results. The repeatability and reproducibility of the method was studied. It was proved that the residence time of the methimazole spot on the TLC plate is time dependent.