Fluorescence quenching titration for determination of complexing capacities and stability constants of fulvic acid

1982 ◽  
Vol 54 (6) ◽  
pp. 986-990 ◽  
Author(s):  
David K. Ryan ◽  
James H. Weber
Keyword(s):  
Fluorescence Quenching ◽  
Fulvic Acid ◽  
Stability Constants ◽  
Fluorescence Quenching Titration

Comparison of Mn2+, Co2+, and Cu2+ binding to fulvic acid as measured by fluorescence quenching

1983 ◽  
Vol 61 (7) ◽  
pp. 1505-1509 ◽  
Author(s):  
David K. Ryan ◽  
Carl P. Thompson ◽  
James H. Weber
Keyword(s):  
Fluorescence Quenching ◽  
Fulvic Acid ◽  
Binding Capacity ◽  
Outer Sphere ◽  
Conditional Stability ◽  
Complexing Capacity ◽  
Fluorescence Quenching Titration ◽  
Conditional Stability Constants ◽  
Slight Advantage ◽  
Binding Curves

The binding of Cu2+ to soil-derived fulvic acid (SFA) measured by fluorescence quenching titration is much stronger than Co2+ and Mn2+ which are similar. The conditional stability constants from curve fitting at pH 6 are 1.1 × 105 for Cu2+, 5.1 × 103 for Co2+, and 4.2 × 103 for Mn2+. The slight advantage in strength for Co2+ over Mn2+ is also demonstrated by the binding curves at pH 6 and 7. These two metal ions not only tend to bind more weakly but also bind to fewer sites, giving complexing capacity values of about 1.5 × 10−6 M compared to 2.0 × 10−5 for Cu2+ at pH 6. This lower binding capacity may be due to outer sphere complexation that does not allow access to some sites complexed by inner sphere binding Cu2+. Scattering experiments demonstrate that Cu2+ is more effective at precipitating and aggregating SFA than Co2+ and Mn2+. Cu2+ probably neutralizes the negative charges on SFA molecules allowing larger hydrophobic aggregates to form and precipitate.

Ultraviolet absorbance titration for the determination of complexing capacities and stability constants of copper (II)-fulvic acid

2006 ◽  
Vol 70 (18) ◽  
pp. A708 ◽  
Author(s):  
F.C. Wu ◽  
Y.C. Bai ◽  
H.X. Zhang ◽  
C.Q. Liu ◽  
L.Y. Wang ◽  
...  
Keyword(s):  
Fulvic Acid ◽  
Stability Constants ◽  
Ultraviolet Absorbance

Determination of stability constants for complexes from catalytic linear scan voltammetric currents

1998 ◽  
Vol 95 (5) ◽  
pp. 1091-1100 ◽  
Author(s):  
J. L. Muñiz Alvarez ◽  
J. A. García Calzón ◽  
J. M. López Fonseca
Keyword(s):  
Stability Constants

scholarly journals Determination of Organic Compounds, Fulvic Acid, Humic Acid, and Humin in Peat and Sapropel Alkaline Extracts

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2995
Author(s):  
Laurynas Jarukas ◽  
Liudas Ivanauskas ◽  
Giedre Kasparaviciene ◽  
Juste Baranauskaite ◽  
Mindaugas Marksa ◽  
...  
Keyword(s):  
Humic Acid ◽  
Fulvic Acid ◽  
Humic Substances ◽  
Organic Compounds ◽  
Chemical Constituents ◽  
Acid Amide ◽  
Extraction Methods ◽  
Ultrasound Extraction ◽  
Different Origins

Black, brown, and light peat and sapropel were analyzed as natural sources of organic and humic substances. These specific substances are applicable in industry, agriculture, the environment, and biomedicine with well-known and novel approaches. Analysis of the organic compounds fulvic acid, humic acid, and humin in different peat and sapropel extracts from Lithuania was performed in this study. The dominant organic compound was bis(tert-butyldimethylsilyl) carbonate, which varied from 6.90% to 25.68% in peat extracts. The highest mass fraction of malonic acid amide was in the sapropel extract; it varied from 12.44% to 26.84%. Significant amounts of acetohydroxamic, lactic, and glycolic acid derivatives were identified in peat and sapropel extracts. Comparing the two extraction methods, it was concluded that active maceration was more efficient than ultrasound extraction in yielding higher amounts of organic compounds. The highest amounts of fulvic acid (1%) and humic acid and humin (15.3%) were determined in pure brown peat samples. This research on humic substances is useful to characterize the peat of different origins, to develop possible aspects of standardization, and to describe potential of the chemical constituents.

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