Studies of Dissolved Black Carbon and Organic Matter Utilizing Electrospray Ionization Mass Spectrometry

Résumé du livre

In this study, ESI FT-ICR MS is also applied to rainwater DOM for the first time, and molecular formulas are determined for more than 80 % of the peaks detected. Elemental composition analysis shows that 36.1% of the compounds consist of CHO only composition, while others contain at least one heteroatom such as nitrogen, sulfur. Among the CHO peaks, atmospheric lipids from C19-C26 were found using two-dimensional van Krevelen diagram and Kendrick analysis as well as showing series of methylation/demethylation. Using three-dimensional van Krevelen diagrams, it is clear that heteroatom(s) play significant roles in rainwater DOM being complementary to oxygen atom(s), which implies that substitution reactions for oxygen atom(s) may occur with heteroatoms. Aside from the characterization of soot DBC and rainwater DOM, direct quantification using ESI responses of compounds in complex mixtures is a challenge. The quantitative aspects of the responses are investigated for the model DOM components including lipid, carbohydrate, peptide, black carbon, uronic acid, catechin and amino sugar groups. The responses are both concentration-dependant and matrix-dependent as well instrumental-dependant and one might not be able to account for all these effects in the ESI process yet. For analysis of complex environmental mixtures, ESI FT-ICR MS is a promising technique. This technique achieves the identification of the elemental composition of compounds contained in DBC in a soot sample and DOM in a rainwater sample. However, it should be noticed that direct quantification of the amounts of the individual compounds in such complex matrices by ESI MS is still challenging that more information on the molecular structure DOM is necessary for future work in the effort to quantify DOM by ESI MS.