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Investigation of the Interaction of Gadolinium with Several Organic Ligands and Humic Acid by Ligand Competition Using 4-(2-Pyridylazo)-Resorcinol (PAR)

Department of Chemistry, University of Nevada, Las Vegas, NV 89154, USA
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Environments 2020, 7(9), 69; https://doi.org/10.3390/environments7090069
Received: 22 July 2020 / Revised: 27 August 2020 / Accepted: 28 August 2020 / Published: 3 September 2020
Gd3+ forms a strongly colored complex with 4-(2-pyridylazo)-resorcinol (PAR) in aqueous solutions. We characterized the Gd3+-PAR complex in order to use it as a probe of Gd3+ speciation in the presence of environmentally relevant ligands. The formation of the Gd3+-PAR complex was investigated from pH 5 to 8 in the presence of excess PAR. The absorbance of the Gd3+-PAR complex dramatically increased from pH 5 to 8 and application of the method of continuous variation indicates that the complex was primarily 1:2 Gd(PAR)2 at pH 8. Stability constants for Gd3+ with other ligands can be quantified by competitive displacement of the PAR ligand. To establish the viability of this approach, we measured the stability constants between Gd3+ and several organic acids and carbonate. Our measurements show reasonable agreement with the literature values. We used the competitive displacement approach to establish that humic acids can competitively displace PAR from the Gd(PAR)2 complex. View Full-Text
Keywords: gadolinium; competitive displacement; 4-(2-pyridylazo)-resorcinol; organic acids; humic acids gadolinium; competitive displacement; 4-(2-pyridylazo)-resorcinol; organic acids; humic acids
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MDPI and ACS Style

Steinberg, S.; Hodge, V.; Becerra-Hernandez, L. Investigation of the Interaction of Gadolinium with Several Organic Ligands and Humic Acid by Ligand Competition Using 4-(2-Pyridylazo)-Resorcinol (PAR). Environments 2020, 7, 69. https://doi.org/10.3390/environments7090069

AMA Style

Steinberg S, Hodge V, Becerra-Hernandez L. Investigation of the Interaction of Gadolinium with Several Organic Ligands and Humic Acid by Ligand Competition Using 4-(2-Pyridylazo)-Resorcinol (PAR). Environments. 2020; 7(9):69. https://doi.org/10.3390/environments7090069

Chicago/Turabian Style

Steinberg, Spencer, Vernon Hodge, and Luis Becerra-Hernandez. 2020. "Investigation of the Interaction of Gadolinium with Several Organic Ligands and Humic Acid by Ligand Competition Using 4-(2-Pyridylazo)-Resorcinol (PAR)" Environments 7, no. 9: 69. https://doi.org/10.3390/environments7090069

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