New methodology to measure low free indium (III) concentrations based on the determination of the lability degree of indium complexes. Assessment of In(OH)3 solubility product
Tehrani, Marjan H.
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The vast industrial and consumer application of indium (solar cells, displays, etc.) risks its eventual leakage to the environment. Given the relevant role of speciation on the ecotoxicological effects of a certain total amount of indium, it is crucial to develop proper techniques to determine free
concentrations of indium. The electroanalytical technique AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) has already proved useful in such a goal. However, the optimization of suitable deposition times in some conditions might be laborious. This work presents a new strategy, based on the technique ADLC (Accumulation under Diffusion Limited Conditions), to determine lability degrees, which apart from their intrinsic physicochemical interest -by comparing reaction kinetics with diffusion rates-, provide useful guidelines for AGNES deposition times. The suggested novel methodology is illustrated with: i) the computation of lability degrees of indium-oxalate complexes (unreported up to date) and ii) measuring free concentration of indium (for the first time as low as pmol L-1) in precipitated solutions (i.e. containing precipitated indium hydroxide in the electrochemical cell). The method takes advantage of the fact that the addition of a suitable concentration of oxalate does not change the free indium concentration (which is buffered due to the existing precipitate at a fix pH), but creates a large amount of labile and mobile indium complexes that contribute to the desired accumulation at very large gains (preconcentration factors). Results confirm the validity of the solubility product of indium hydroxide reported in the database NIST 46.7
Is part ofJournal of Electroanalytical Chemistry, 2019, vol. 847, p. 113185
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