Universal charge-tag labelling of undetectable polymers for mass spectrometric characterization.

Despite massive advances in mass spectrometric technologies, there remains a class of materials largely impervious to analysis: high molecular weight aliphatic hydrocarbons. Electrospray ionization mass spectrometry (ESI-MS) is used extensively as a tool in petroleomics to identify and fingerprint the polar constituents of oil, but the non-polar constituents remain challenging to analyze with ESI-MS due to poor ionization efficiency. Derivatization methods which bond electrospray-active tags to analytes impart charge and increase analyte response and have been developed for many different classes of petrochemicals, but not hydrocarbons. In this work, a method is described which renders aliphatic hydrocarbons amenable to ESI-MS analysis through C-H insertion into a substrate molecule of a diazirine-derived carbene, which is bound to a pendant alkyne. Subsequent electrospray-tagging occurs through copper-catalyzed azide alkyne cycloaddition, appending a triphenylphosphonium cation to the derivatized compound. The process was developed and benchmarked with cyclododecane as a model substrate to evaluate tagging efficiency and product distribution and then applied to characterize several commercial products composed of aliphatic compounds. While derivatization efficiency and ionization response may vary across substrates, the method provides a complementary route to established ionization techniques by enabling hydrocarbon analysis within ESI-based high-resolution mass spectrometric workflows. Its primary utility lies in enabling ESI-compatible fingerprinting of unfunctionalized compounds.