Sorption of Aldrich Humic Acids onto Hematite: Insights into Fractionation Phenomena by Electrospray Ionization with Quadrupole Time-of-Flight Mass Spectrometry

Pascal E. Reiller (1) , Badia Amekraz (1) , Christophe Moulin (1)

1 LSRM - Laboratoire de Spéciation des Radionucléides et des Molécules

Sorption induced fractionation of purified Aldrich humic acid (PAHA) on hematite is studied through the modification of electrospray ionization (ESI)quadrupole time-of-flight (QToF) mass spectra of supernatants from retention experiments. The ESI mass spectra show an increase of the “mean molecular masses” of the molecules that constitutes humic aggregates. The low molecular weight fraction (LMWF; m/z ≤ 600 Da) is preferentially sorbed compared to two other fractions. The resolution provided by ESI-QToF mass spectrometer in the low-mass range provided evidence of further fractionation induced by sorption within the LMWF. Among the two latter fractions, the high molecular weight fraction (HMWF; m/z ≈ 1700 Da) seems to be more prone to sorption compared to the intermediate molecular weight fraction (IMWF; m/z ≈ 900 Da). The IMWF seems to be more hydrophilic as it should be richer in O, N and alkyl C from the proportion of even mass, and poorer in aromatic structures from mass defect analysis in ESI mass spectra.

Keywords: Humic Substances; Fractionation; Retention; Iron Oxides; ESI-MS

Domains: Inorganic chemistry

Pascal E. Reiller, Badia Amekraz, Christophe Moulin. Sorption of Aldrich Humic Acids onto Hematite: Insights into Fractionation Phenomena by Electrospray Ionization with Quadrupole Time-of-Flight Mass Spectrometry. Environmental Science and Technology, 2006, 40 (7), pp.2235-2241. ⟨10.1021/es0520518⟩. ⟨cea-00278013⟩