Abstract
Electrochemical pre-concentration has been shown to effectively increase sample sensitivity and decrease processing time; however, the basic mechanism and optimal conditions of the technique remain unknown, specifically for lanthanides. To gain a better understanding of the mechanism of action, the aqueous solution conditions required to maximize the electrochemical pre-concentration of lanthanum (La) were studied. Parameters investigated included pH, applied potential, and ionic strength. To further optimize and elucidate the mechanism of lanthanide pre-concentration, specific interactions of lanthanum with the mercury film electrode were studied. Three possible mechanisms were proposed based on preliminary observations, including ligand bridging, hydroxide formation, and amalgamation.
Acknowledgement
J. L. D. would like to thank Dr. Francis Cheng of the University of Idaho and Dr. Mark Engelmann of Pacific Northwest National Laboratory for their advice and suggestions on the electrochemistry. The authors would like to thank Charles Knaack and Scott Boroughs at the Washington State University GeoAnalytical Laboratory for their assistance in the ICP-MS measurements. The authors would also like to thank Academic Research Initiative of the Joint Domestic Nuclear Detection Office, Department of Homeland Security, and the National Science Foundation, for funding under Grant Numbers ECCS-0833548 and DN-077-ARI-03302. S. B. C. also acknowledges support from DHS and NSF as described above, and the Defense Threat Reduction Agency, grant number HDTRA-1-14-10069.
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