HPLC–UV–MS Analysis: A Source for Severe Oxidation Artifacts

HPLC coupled to both UV and MS is an established setup for purity assessments in many areas. With evolving technology, instrument sensitivity increases, calling for lower sample concentration, while light flux in a commercial UV detector cell is considerably higher than earlier. This evolution has now reached the point where radicals formed by UV light are abundant enough, compared to the analyte levels, to generate unwanted artifact signals in the MS spectrum. In this work we show several examples from pharmaceutical development where UV degradation in the UV detector leads to severely misleading mass spectra in typical day to day samples.