Investigation of the Electrostatic Properties of Humic Substances by Fluorescence Quenching

Sarah A. Green; Francois M. M. Morel; Nell V. Blough

doi:10.1021/es00026a008

Investigation of the Electrostatic Properties of Humic Substances by Fluorescence Quenching

Sarah A. Green, Francois M. M. Morel, Nell V. Blough

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84 Scopus citations

Abstract

A fluorescence quenching technique was employed to explore the electrostatic properties of fulvic acid (FA) and humic acid (HA). Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. This result is attributed to the enhanced Coulombic attraction of cations to the anionic FA or HA surface and is interpreted as an estimate of surface potential. Reduction of molecular charge at low pH and shielding of charge at high ionic strength produced diminished enhancements, consistent with this interpretation. High molecular weight fractions of HA have a higher apparent surface potential than lower molecular weight fractions, indicating that larger humic molecules may have an enhanced ability to bind metal ions.

Original language	English (US)
Pages (from-to)	294-302
Number of pages	9
Journal	Environmental Science and Technology
Volume	26
Issue number	2
DOIs	https://doi.org/10.1021/es00026a008
State	Published - Feb 1 1992

All Science Journal Classification (ASJC) codes

General Chemistry
Environmental Chemistry

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10.1021/es00026a008

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title = "Investigation of the Electrostatic Properties of Humic Substances by Fluorescence Quenching",

abstract = "A fluorescence quenching technique was employed to explore the electrostatic properties of fulvic acid (FA) and humic acid (HA). Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. This result is attributed to the enhanced Coulombic attraction of cations to the anionic FA or HA surface and is interpreted as an estimate of surface potential. Reduction of molecular charge at low pH and shielding of charge at high ionic strength produced diminished enhancements, consistent with this interpretation. High molecular weight fractions of HA have a higher apparent surface potential than lower molecular weight fractions, indicating that larger humic molecules may have an enhanced ability to bind metal ions.",

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year = "1992",

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AU - Green, Sarah A.

AU - Morel, Francois M. M.

AU - Blough, Nell V.

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Y1 - 1992/2/1

N2 - A fluorescence quenching technique was employed to explore the electrostatic properties of fulvic acid (FA) and humic acid (HA). Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. This result is attributed to the enhanced Coulombic attraction of cations to the anionic FA or HA surface and is interpreted as an estimate of surface potential. Reduction of molecular charge at low pH and shielding of charge at high ionic strength produced diminished enhancements, consistent with this interpretation. High molecular weight fractions of HA have a higher apparent surface potential than lower molecular weight fractions, indicating that larger humic molecules may have an enhanced ability to bind metal ions.

AB - A fluorescence quenching technique was employed to explore the electrostatic properties of fulvic acid (FA) and humic acid (HA). Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. This result is attributed to the enhanced Coulombic attraction of cations to the anionic FA or HA surface and is interpreted as an estimate of surface potential. Reduction of molecular charge at low pH and shielding of charge at high ionic strength produced diminished enhancements, consistent with this interpretation. High molecular weight fractions of HA have a higher apparent surface potential than lower molecular weight fractions, indicating that larger humic molecules may have an enhanced ability to bind metal ions.

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ER -

Investigation of the Electrostatic Properties of Humic Substances by Fluorescence Quenching

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