Quantitative determination of propranolol in plasma and pharmaceutical preparations by agar-based cation-exchange...

A new cost-effective method for determining the amount of total propranolol (free and protein-bound) in plasma samples and the amount of the drug in tablets and injection solutions has been developed. The method is based on cation-exchange chromatography at pH 8.5 on an inexpensive column of agar, the native sulfate (and carboxylic) groups of which interact with the positively charged propranolol (this interaction is reinforced by the 'aromatic adsorption' characteristic of the agar matrix). The method can be used for quantitative analyses at both low (1 x 10(-2) mg/L) and high (5 x 10(3) mg/L) concentrations of the drug. For analyses of plasma and tablets--but not for injection solutions--extraction of the propranolol is required. The extraction time was 6 min. On a 6(ID) mm x 9 mm agar column the run time was less than 10 min.