Spectrophotometric determination of methoxamine using cerium(IV) in presence of sodium lauryl sulphate and rhodamine-B

A sensitive spectrophotometric assay has been developed for the determination of methoxamine in pure dosage form and in its pharmaceutical preparations. The method is based on the acidic oxidation of methoxamine with cerium(IV) in the micellar medium of sodium lauryl sulphate at 96 degrees C. The reaction yields a water-soluble purple product which can be quantified spectrophotometrically at 505 nm. The calibration curve was linear between 1.0 and 20 mu g ml(-1) with a limit of detection 0.5 mu g ml(-1). The molar absorptivity at 505 nm is 8.3 x 10(3) lmol(-1) cm(-1). The method is simple and rapid since the product is measured directly in solution without extraction. (C) 1997 Elsevier Science B.V.