(–)-Adrenaline, adrenaline hydrogen tartrate, L-noradrenaline, dopamine hydrochloride, L-dopa, DL-dopa, L-α-methyldopa, D-α-methyldopa and (+)-Corbasil have been determined in amounts down to 0·0001 mequiv by catalytic thermometric titration of their basic and acidic functions. Basic functions were determined by titration with 0·1, 0·01 and 0·001 M perchloric acid by using the ionic polymerisation of α-methylstyrene to indicate the end-point, while acidic functions were determined in a similar manner with tetra-n-butylammonium hydroxide as the titrant and acrylonitrile as the end-point indicator.

The L-dopa contents of tablets and capsules have been determined by using these techniques and the assay results have been compared with those obtained by alternative methods, namely, the recently described B.P. procedure involving non-aqueous titration, and ultraviolet spectrophotometry.

Magnesium stearate, which is used as a lubricant and flow promoter in tablet manufacture, is titrated as a base in the solvents used, but in titrations of the acidic function of catecholamines its effect is negligible.