Dimethylcarbazoles in Crude Oils: Comment on 'Liquid Chromatographic separation schemes for Pyrrole and Pyridine Nitrogen Aromatic Heterocycle Fractions from Crude Oils Suitable for Rapid Characterization of Geochemical Samples'

摘要

SIR: In an evaluation of chromatographic methods for the isolation of pyrrolic and pyridinic nitrogen compounds from crude oils, Li et al. reported peak assignments for carbazole, the methylcarbazoles, and several C_2-alkylcarbazolse. During standard compound coinjection studies using gas chromatog- raphy/mass spectrometry, we became aware that the peak assignments reported by Li et al.~1 for several of the C_2 - alkylcarbazoles are incorrect.