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Open AccessArticle

Macromolecular Structure of a Commercial Humic Acid Sample

1
Environmental Technologies, University Spin-Off of the University of Campania “Luigi Vanvitelli”, Via Vivaldi, 43, 81100 Caserta, Italy
2
Department of Engineering, University of Campania “Luigi Vanvitelli”, via Roma 29, 81031 Aversa, Italy
3
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania “Luigi Vanvitelli”, via Vivaldi 43, 81100 Caserta, Italy
*
Author to whom correspondence should be addressed.
Environments 2020, 7(4), 32; https://doi.org/10.3390/environments7040032
Received: 6 March 2020 / Revised: 10 April 2020 / Accepted: 13 April 2020 / Published: 15 April 2020
(This article belongs to the Special Issue Feature Papers in Environments in 2020)
The molecular structure of a commercial sample of humic acids (HA) was investigated by membrane dialysis experiments (MD) and low-pressure size-exclusion chromatography (LP-SEC). MD showed that HA molecules were retained by dialysis membrane with a cut-off of 6–8 kDa, independently from HA concentration (15 or 150 mg L−1), NaHCO3 concentration (0.005–2.0 mol L−1), and from propan 2-ol (0–5 v/v %). SEC experiments at low pressure gave chromatograms with a broad peak, with an elution volume between those of the globular proteins bovine serum albumin (molecular weight = 66.5 kDa) and lysozyme from egg (molecular weight = 14.4 kDa). The pattern of the chromatogram did not vary with HA concentration, and second-run chromatograms of single eluted fractions showed relatively sharp peaks. From these data, we reveal that the commercial HA sample analysed has a macromolecular structure rather than being a supramolecular aggregate of relatively small molecules, as recently proposed for some samples of HA obtained from different sources. View Full-Text
Keywords: humic substances; molecular structure; supramolecular aggregate; exclusion chromatography humic substances; molecular structure; supramolecular aggregate; exclusion chromatography
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Capasso, S.; Chianese, S.; Musmarra, D.; Iovino, P. Macromolecular Structure of a Commercial Humic Acid Sample. Environments 2020, 7, 32.

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