title: Exploring the high-mass components of humic acid by laser desorption ionization mass spectrometry.
abstract: Leonardite and Elliot soil humic acids have been analyzed by laser desorption ionization mass spectrometry (LDI MS) in the m/z 4000-200,000 range. Positive ion mass spectra for each humic acid obtained under optimum conditions showed a broad high-mass distribution between m/z 20,000 and 80,000. The dependence of the mass distribution on instrumental parameters and solution conditions was used to investigate the nature of the high-mass peaks from humic acid spectra. Our data suggests that macromolecular ions and humic acid aggregates have the same probability of occurrence while cluster ion formation has a low probability of occurrence.
authors.affiliation: Department of Chemistry & Biochemistry, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Chilom
authors.forename: Ovidiu
authors.initials: O
authors.lastname: Chilom
authors.forename: James A
authors.initials: JA
authors.lastname: Rice