Determination of kinetic parameters of redox reactions using CE‐ICP‐MS: A case study for the reduction of Np(V) by hydroxylamine hydrochloride

摘要

Abstract The rate constants k of the reduction of 5?×?10 –5 ?M Np(V) to Np(IV) by hydroxylamine hydrochloride (HAHCl) in 1 M HCl have been determined by CE‐ICP‐MS in the temperature range of ??= 30–70°C and with varying concentrations of HAHCl from 1 to 7.2?M. The reaction was found to have (pseudo)first order kinetics with respect to HAHCl. The experimental results for k ranged from 0.0029(1)?min ?1 (??=?40°C, c (HAHCl)?=?3?M) to 0.039(7)?min ?1 (??=?60°C, c (HAHCl)?=?7.2?M). The activation energy of the reaction was determined as E A ?=?(72?±?10)?kJ/mol. These results and a comparison with literature data show that the coupling of CE to ICP‐MS provides a powerful analytical tool for the investigation of the kinetic aspects of redox reactions of actinides at low concentrations. On the basis of this proof‐of‐principle study, the method presented here can be extended to the investigation of the kinetic parameters of other redox systems containing different actinides (or transition metals) and oxidants/reductants.