Determination of isoproterenol sulfate on surfaces using high-performance liquid chromatography with electrochemical detection

Abstract

Trace amounts of isoproterenol (IP) sulfate are determined on surfaces using high-performance liquid chromatography with electrochemical detection (LC-ED). The drug residues are removed from surfaces with cotton swabs using an aqueous buffer which is 0.05 M phosphate, 5 m M pentanesulfonic acid and 0.1 m M EDTA at pH 3.6. The drug substance is chromatographed using a 15 cm × 4.6 mm I.D. Nucleosil C 18 column and an eluent containing the same buffer and methanol as a modifier which are mixed in a 90:10 ratio. Detection is performed using an amperometric thin-layer cell with a glassy carbon working electrode operated at +0.65 V versus Ag/AgCl which gives a linear response ( r = >0.9999) for isoproterenol sulfate to at least 42.9 ng/ml. Repeatability of the chromatographic finish was demonstrated by replicately chromatographing IP solutions over several days. Repeatability (R.S.D. values) of the peak areas ranged from ±0.32% to ±3.0%. For additions of 40 to 120 ng of isoprotenol sulfate average recoveries from cotton swabs ranged from 82 to 98%. At the same addition levels. average recoveries ranged from 87% to 95% for stainless steel and glass surfaces. The precision for all recovery data (R.S.D. values) ranged from ±2.1% to 12.8%.