Spectrophotometric and fluorimetric determination of aztreonam in bulk and dosage forms

Spectrophotometric and fluorimetric determination of aztreonam were achieved through its reaction with cerium (IV) in acidic medium. The spectrophotometric method involves the quantitation of the amount of ceric equivalent to aztreonam by measuring the absorbance at 317 nm and the corresponding first-derivative value at 284 nm for the blank solution against the reaction solution. Beer's law is obeyed over the concentration ranges of 1.5-4 and 1-4 microg ml(-1), respectively. Meanwhile, in the fluorimetric method, higher sensitivity was achieved by measuring the fluorescence intensity of the formed cerium (III) at lambda(em)=357 nm (lambda(ex)=257 nm) within a concentration range 150-350 ng ml(-1). Study of the reaction conditions and reaction stoichiometry were presented. Interference from L-arginine, which is frequently co-formulated with aztreonam, was tested. The proposed procedures were applied successfully to the determination of aztreonam in pure form and in presence of arginine both in laboratory mixtures and commercial vials. The proposed methods are sensitive, accurate and precise as compared with the official USP 24 HPLC method.