Peak Purity and Spectral Matching During Validation of LC Methods

Shulamit Levin, Waters (TC) Israel, Petech Tikva.
Peak purity and spectral matching by Photo Diode Array (PDA) detectors has been used for years as part of LC method validation in the specificity step, indicating that analyte peaks contain no hidden components in them and can be used for Assays or Stability studies.  In recent years it was shown time and again that this tool might not be enough in some cases, where the related compounds of the major Active Pharmaceutical Ingredient (API) have very similar UV spectrum.
A striking example will be described, part of Validation of a UPLC method for related compounds of Metoclopramide HCl in Drug Tablet Formulation, in which one of the related compounds has identical UV spectrum as the main API, therefore, its presence can be detected only by using a Mass Spectrometry (MS) detection in addition to the PDA detection, for accurate peak purity and spectral matching.