This study establishes a robust framework for the structural elucidation of trace-level impurities in organic electronic materials, where authentic reference standards are often unavailable. We present the application of infrared ion spectroscopy (IRIS) in this domain, introducing a fragment-centric strategy that enables confident structural assignment by probing mass-selected fragment ions and leveraging partial structural similarities. By focusing on diagnostically informative substructures, this strategy circumvents the need to synthesize the putative impurity as a reference compound, which may be costly or impossible. In a trace-level brominated impurity found in organic light-emitting diode host materials, which causes a reduction in device lifetime, our IRIS-based analytical strategy identified a meta-substitution pattern that provided a critical clue to the origin of the impurity. The structural assignment of the substructure was supported by density functional theory-based spectral simulations and confirmed using a reference material. Our analytical strategy is broadly applicable to impurity profiling in various fields, including drug development, environmental analysis, forensic investigations, and clinical diagnostics, where sparse, structurally ambiguous compounds can pose serious analytical challenges.
Takano et al. (Sat,) studied this question.