ESI-MS analyses of lake dissolved organic matter in light of supramolecular assembly.

摘要: A high-performance size-exclusion chromatography (SEC) system was coupled on-line to an electrospray ionization (ESI) interface detect gas-phase ions by API 365 LC/MS/MS triple quadrupole analyzer. The SEC fractions of a strongly coloured freshwater solution containing dissolved organic matter-humic substances (DOM-HS) were screened both UV(254) and ESI mass spectrometry (ESI-MS) in the full-scan mode within m/z range 100-2,900 amu negative positive polarities. ESI-MS spectra also collected direct infusion DOM-HS did not primarily favour low compounds, total ion chromatograms parallel elution profile obtained detection from solution. overestimated portion higher size/mass solutes underestimated that smaller sizes/masses as compared with chromatogram intensities or change mass-weighted number-weighted average (M(w) M(n)) different fairly small, contrast detection, increasing volume. reasonable explanation for great differences between M(w) M(n) values, detections eight fractions, seems be supramolecular-type association relatively small components through weak dispersive forces. values vapour-pressure osmometry some extent analogous those ESI-MS. shapes either polarities calculated indicated close structural similarity each fraction. Positive humic represented quite similar components, there no evidence noteworthy occurrence multiply charged being able lower distributions spectra. effect nitrogen on seemed unimportant, observed at even correspond most likely (13)C counterparts more abundant (12)C odd ions. No uncontrolled fragmentation observable heat-resistant. Direct untreated statistical calculation verified SEC-separated really represent distinct entities original mixture. results support opinion composition their combined mixture resembles associations molecular size possessing functionalities.