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Open AccessArticle

Macromolecular Structure of a Commercial Humic Acid Sample

Environmental Technologies, University Spin-Off of the University of Campania “Luigi Vanvitelli”, Via Vivaldi, 43, 81100 Caserta, Italy
Department of Engineering, University of Campania “Luigi Vanvitelli”, via Roma 29, 81031 Aversa, Italy
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;
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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