Phase-Resolved Fluorescence Spectral and Lifetime Characterization of Commercial Humic Substances

Hemmingsen, Sherry L.; McGown, Linda B.

doi:10.1366/0003702971941458

Cited by 27 publications

(12 citation statements)

References 26 publications

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“…This result is consistent with that reported in literature for IHSS reference humic substances 48 and is also consistent with measurements of fluorescence lifetime of HS, showing three distinct values. 49 Figure 4 shows contour maps of the different fluorophores for EHA and FHA, which are similar to others HA. 13,48,50 The components have been named starting from the emission maximum with the higher wavelength, the spectra showing only a small dependence with pH and ionic strength; Table S2 (SI) collects the average peak emission and excitation wavelengths for FHA and EHA.…”

Section: ■ Results and Discussionsupporting

confidence: 66%

Pb(II) Binding to Humic Substances: An Equilibrium and Spectroscopic Study

Orsetti

Marco-Brown²,

Andrade³

et al. 2013

Environ. Sci. Technol.

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The binding of Pb(II) to humic acids is studied through an approach combining equilibrium and spectroscopic measurements. The methods employed are potentiometric and fluorometric titrations, fluorescence excitation-emission matrices (EEM) and IR spectroscopy. Potentiometric titration curves are analyzed using the NICA equations and an electrostatic model treating the humic particles as an elastic polyelectrolyte network. EEMs are analyzed using parallel factor analysis, decomposing the signal in its independent components and finding their dependence on Pb(II) activity. Potentiometric results are consistent with bimodal affinity distributions for Pb(II) binding, whereas fluorometric titrations are explained by monomodal distributions. EEM analysis is consistent with three independent components in the humic fluorescence response, which are assigned to moieties with different degree of aromaticity. All three components show a similar quenching behavior upon Pb(II) binding, saturating at relatively low Pb(II) concentrations. This is attributed to metal ion induced aggregation of humic molecules, resulting in the interaction between the aromatic groups responsible for fluorescence; this is also consistent with IR spectroscopy results. The observed behavior is interpreted considering that initial metal binding (observed as strongly binding sites), correspond to bi- or multidentate complexation to carboxylate groups, including binding between groups of different humic molecules, promoting aggregation; further metal ions (observed as weakly binding sites) bind to single ligand groups.

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Section: ■ Results and Discussionsupporting

confidence: 66%

Pb(II) Binding to Humic Substances: An Equilibrium and Spectroscopic Study

Orsetti

Marco-Brown²,

Andrade³

et al. 2013

Environ. Sci. Technol.

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“…The work of Mobed et al (1996) is very highly recommended for a rigorous examination of the total luminescence spectra of DOM and related materials and for a clear illustration of the necessity for basing interpretations of the solution chemistry of DOM on corrected spectra. Hemmingsen and McGown (1997) have extended this work using phase-resolved fluorescence intensity to explore the fluorescent lifetimes of the complex mixture of fluorophores in HAs. Marhaba et al (2000) have measured the total luminescence spectra of the six fractions of DOM that can be obtained using the fractionation procedure of Leenheer and Huffman (1976), which is described in Section 7.8.4.2.1.…”

Section: Dom and Uv-visible Radiationmentioning

confidence: 99%

Dissolved Organic Matter in Freshwaters

Perdue

Ritchie

2014

Treatise on Geochemistry

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“…Since the early 1990s the timeresolved laser fluorescence spectroscopy (TRLFS) has been applied to quantify and to elucidate Cm(III)-HA/FA interaction [1,3,[6][7][8][9][10][11]. The trivalent actinide ion Cm(III) exhibits outstanding features as a fluorescent probe with high fluorescence yield thus allowing speciation in the low nano-molar concentration range [9,12]. From TRLFS studies and fluorescence lifetime analysis, Cm(III) binding to 3 carboxylate sites in a bidentate manner has been concluded [13].…”

Section: Introductionmentioning

confidence: 99%

Influence of pH and metal ion loading on the Cm(III) humate complexation: a time resolved laser fluorescence spectroscopy study

Rabung¹,

Geckeis

2009

Radiochimica Acta

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Interaction of trivalent lanthanides and Cm(III) with humic acid (HA) (10 mg/L) is studied as a function of metal ion concentration (1 × 10 −8 to 5 × 10 −5 mol/L) and pH (2.5 to 7.0) in 0.01 mol/L NaClO 4 . Time resolved laser fluorescence spectroscopy (TRLFS) reveals a slight blueshift/broadening of the fluorescence peak position for the Cm(III)-HA complex combined with an enhanced contribution of a short-lived fluorescence component with increasing metal ion loading and decreasing pH. Fluorescence decay for Cm(III)-HA is non-monoexponential under all investigated conditions and lifetimes can be described by assuming a short lived (τ = 61 µs) and a longer lived contribution (τ = 142 µs). These findings are explained by the existence of a certain heterogeneity in binding sites inducing slightly variable ligand-field splitting in the Cm(III)-HA complex. Batch experiments with a Eu(III)-HA solution contacted with a chelating resin reveal a decrease of the solid/liquid distribution coefficient by decreasing the occupancy of HA ligand sites from 4% to 0.2%. This observation indicates that complexation constants for the Eu(III)-HA complex vary with metal loading. Differences in related constants are, however, smaller than one order of magnitude. Variations in fluorescence lifetimes are interpreted as a consequence of increasing HA agglomeration at increasing metal loading and decreasing pH, thus leading to an enhanced local density of chromophoric groups close to the Cm(III) ion favouring nonradiative energy transition. HA agglomeration at low pH and increasing metal ion loading is well known from previous studies using flow-field flow fractionation (FFF) coupled to ICP-mass spectrometry and UV-Vis spectrophotometry. Our experimental results demonstrate the dynamic properties of metal-HA complexes depending on chemical conditions.

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Phase-Resolved Fluorescence Spectral and Lifetime Characterization of Commercial Humic Substances

Cited by 27 publications

References 26 publications

Pb(II) Binding to Humic Substances: An Equilibrium and Spectroscopic Study

Pb(II) Binding to Humic Substances: An Equilibrium and Spectroscopic Study

Dissolved Organic Matter in Freshwaters

Influence of pH and metal ion loading on the Cm(III) humate complexation: a time resolved laser fluorescence spectroscopy study

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