Fragmentation Reactions of Rhodamine B and 6G as Revealed by High Accuracy Orbitrap Tandem Mass Spectrometry

Correct interpretation of mass spectra is essential to our understanding of the ion chemistry occurring in the gas phase inside mass spectrometers and for constructing a solid knowledge from which mass spectrometry (MS) data of novel molecules will be interpreted. Assignments of product ions leading to incorrect dissociation mechanisms can also be dangerous in several disciplines such as in forensic chemistry and clinical diagnostics. Main fragmentation routes for rhodamines B and 6G were investigated by high accuracy Orbitrap tandem mass spectrometry (MS/MS). Isobars were properly resolved and molecular formulas were correctly attributed to all major product ions. This proper evaluation of ions composition and formula allowed us to propose a detailed mechanism for their dissociation. A comprehensive mechanistic fragmentation is proposed for rhodamine B and 6G using product ion assignments resulting from high resolution and accuracy tandem MS data, which should serve as a guide for MS and MS/MS data interpretation of homologues molecules.