The investigation of the birch tar using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and Hydrogen/Deuterium exchange approach

Birch tar was widely used since the Stone Age as adhesive, disinfectant, mosquito repellent etc. Despite of this, the chemical composition of the birch tar remains largely unknown. Here we implement the electrospray ionization ultrahigh resolution Fourier transform mass spectrometry for the determination of the molecular formulas of the birch tar constituents. It was found that in the positive ESI mode the compounds containing 2 nitrogen atoms dominates in the spectrum. Compounds containing 1 nitrogen atom were detected too but they are less abundant. In the negative ESI mode the compounds containing from 2 to 4 oxygen atoms were detected. Also, we used recently developed in-ESI source Hydrogen/Deuterium exchange approach for the structural characterization of the individual molecules. We observed the 1 H/D exchange for major O₃ compounds and did not observe H/D exchange for almost all O₂ compounds. Corresponding neutral molecules have 2 and 1 labile hydrogens and as a consequence -OH groups respectively.