Quantitative and structural determination of pseudoephedrine sulfate and its related compounds in pharmaceutical...

A simple isocratic reversed-phase high performance liquid chromatograghic method for the separation of pseudoephedrine and its related compounds in pharmaceutical formulations is described. The separation is achieved in less than 35 min on a C-18 column (4.6 mm I.D. x 25 cm length, 5-micrometer particle size) using a mobile phase consisting of a mixture of ammonium acetate and methanol. The results described in this report demonstrate that the method is sensitive and selective. Structural elucidation of two new pseudoephedrine degradation products is described. On the basis of structural analysis by liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-nuclear magnetic resonance spectroscopy (LC-NMR), the two newly elucidated degradation products were identified to be 2-(carboxyamino)propiophenone (molecular ion of m/z=194) and 2-formyl-2-(methylamino)-acetophenone (molecular ion of m/z=178).