Automated flow-injection spectrophotometric determination of catecholamines (epinephrine and isoproterenol) in pharmaceutical formulations based on ferrous complex formation.

A novel automated flow-injection spectrophotometric method for the determination of catecholamines (epinephrine and isoproterenol) has been developed based on the formation of their coloured complexes with Fe(II) in aminoacetic-carbonate buffer pH 8.3 and measuring of the absorbance peaks at the lambda(max) of 530 nm. A fully automated FIA system controlled by home-made software (FIA-MOD) was used for optimising the chemical and manifold parameters and running of routine measurements. The calibration graph was linear in the range of 5-200 mg l(-1) for epinephrine with an RSD of 0.24% (n = 5; c = 150 mg l(-1)) and 10-300 mg(-1) for isoproterenol with an RSD of 0.13% (n = 5; c = 200 mg l(-1)). Measurement throughput was 120 h(-1) ensuring a sample throughput of 40 h(-1) analysed in triplicate. Common excipients for tablets and injections were found not interfering. The proposed method was applied for the assay of various commercial pharmaceutical formulations containing epinephrine and isoproterenol and for the content uniformity test for the isoproterenol tablets. The assay results with RSD 2-4% (n = 3) were comparable with those obtained with the official USP XXIII methods (mean difference 1.9%).