At the heart of every liquid-liquid separation process for metal ions is selective complex formation in aqueous and/or organic media. Although thermodynamics drives the complex formation, these parameters give no information about the mechanism by which these reactions take place. To determine such information, reaction kinetics need to be studied. The use of chromotropic dyes such as Arsenazo-III (AAIII), Chlorophosphonazo-III (ClPA), and Xylenol Orange (XO) are often used for metal ligand binding kinetic studies. To determine their efficacy for use with Lanthanide metals, we have studied Lanthanum (Ln) binding with 1,2-Cyclohexanediaminetetraacetic Acid (CDTA). Typically, Ln-CDTA binding kinetics cannot be measured directly via UV-Vis spectrophotometry due to the weak nature of the absorption bands in the 4f elements being laporte forbidden. In this presentation we will discuss how each chromotropic dye affects the kinetics of the Ln-CDTA complex formation, effectively slowing the reaction to allow for monitoring by conventional UV-Vis spectrophotometry.

Survey of the chromotropic dyes arsenazo-iii, chlorophosphonazo-iii, and xylenol orange for use in lanthanum binding kinetic determinations with 1,2-cyclohexanediaminetetraacetic acid (CDTA)

251st National Meeting (2016)

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