Molecular characterization of naphthenic acids from heavy crude oils using MALDI FT-ICR mass spectrometry

摘要: Abstract Naphthenic acid (NA) fractions from heavy crude oils are typically analyzed in mass spectrometry via electrospray ionization (ESI). Here, we show that NA analysis is also possible by MALDI using a highly basic matrix (proton sponge). When compared with ESI, allowed detection of six compound families, resulted the observation twenty-two families. Besides, affords compositional-dependent information. Unlike where all NAs detected as deprotonated molecules, observe both molecules and radical anions. This indicates ion formation can occur either acid-base electron-capture mechanisms, or both. Interestingly, preferred channel seems to be class dependent; for instance, base mechanism (which allows species through Bronsted-Lowry reaction) applies exclusively high H/C ratios along whole O/C range. On other hand, less saturated compounds mechanisms apply, while electron capture occurs low (envelope van Krevelen plots). In summary, demonstrate MALDI(-) an alternative method complex petrochemical samples offering additional advantages, when such increasing compositional space accessibility polar samples, throughput exceptional tolerance presence impurities salts samples. Furthermore, exploration on semi-quantitative approaches provide advantages those offered LC-ESI MS, currently used quantify naphthenic acids.