A spectropolarimetric assay of (-)-adrenaline in compendial formulations.

A method is described for the determination of (-)-adrenaline in certain formulations containing adrenaline hydrogen tartrate at concentrations down to 0.18 mg ml-1 (1:10 000 adrenaline). The assay is based upon a spectropolarimetric measurement at 249 nm of sample solutions, suitably treated to remove interfering substances. The rotation of the sample solutions is corrected for the rotation of the tartaric acid species which is determined by a difference rotation measurement on equimolar sample solutions at pH 1.1 and pH 5.6. The concentration of (-)-adrenaline in the sample is calculated from the net rotation at 249 nm due to the (-)-adrenaline and the total concentration of adrenaline (+)-and (-)-isomers) determined by a published spectrofluorimetric method. The assay is specific for (-)-adrenaline in the presence of (+)-adrenaline, (+)-tartaric acid, adrenaline sulphonic acid and low levels of adrenochrome.