Identification, Isolation, and Characterization of a New Degradation Impurity in Nafcillin Sodium

A new degradant of Nafcillin Sodium was found at a level of 1.8% w/w during the gradient reversed-phase HPLC analysis in stability storage samples. This impurity was identified by LC-MS and was characterized by ¹H-NMR, ¹³C-NMR, LC/MS/MS, elemental analysis, and IR techniques. Based on the structural elucidation data, this impurity was named as N-[(2S)-2-carboxy-2-{[(2-ethoxy-naphthalen-1-yl)carbonyl]amino}ethylidene]-3-({N-[(2-ethoxynaphthalen-1-yl)-carbonyl]glycyl}sulfanyl)-D-valine. This impurity was prepared by isolation and was co-injected into the HPLC system to confirm the retention time. To the best of our knowledge, this impurity has not been reported elsewhere. The identification and structural elucidation of this degradant impurity has been discussed in detail.