title: Miniaturizing and automation of free acidity measurements for uranium (VI)-HNO3 solutions: Development of a new sequential injection analysis for a sustainable radio-analytical chemistry.
abstract: A miniaturized and automated approach for the determination of free acidity in solutions containing uranium (VI) is presented. The measurement technique is based on the concept of sequential injection analysis with on-line spectroscopic detection. The proposed methodology relies on the complexation and alkalimetric titration of nitric acid using a pH 5.6 sodium oxalate solution. The titration process is followed by UV/VIS detection at 650nm thanks to addition of Congo red as universal pH indicator. Mixing sequence as well as method validity was investigated by numerical simulation. This new analytical design allows fast (2.3min), reliable and accurate free acidity determination of low volume samples (10µL) containing uranium/[H(+)] moles ratio of 1:3 with relative standard deviation of <7.0% (n=11). The linearity range of the free nitric acid measurement is excellent up to 2.77molL(-1) with a correlation coefficient (R(2)) of 0.995. The method is specific, presence of actinide ions up to 0.54molL(-1) does not interfere on the determination of free nitric acid. In addition to automation, the developed sequential injection analysis method greatly improves the standard off-line oxalate complexation and alkalimetric titration method by reducing thousand fold the required sample volume, forty times the nuclear waste per analysis as well as the analysis time by eight fold. These analytical parameters are important especially in nuclear-related applications to improve laboratory safety, personnel exposure to radioactive samples and to drastically reduce environmental impacts or analytical radioactive waste.
authors.affiliation: CEA Nuclear Energy Division, Radiochemistry & Processes Department, Marcoule, F-30207 Bagnols-sur-Cèze, France.
authors.forename: José
authors.initials: J
authors.lastname: Néri-Quiroz
authors.affiliation: CEA Nuclear Energy Division, Radiochemistry & Processes Department, Marcoule, F-30207 Bagnols-sur-Cèze, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Canto
authors.affiliation: CEA Nuclear Energy Division, Radiochemistry & Processes Department, Marcoule, F-30207 Bagnols-sur-Cèze, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Guillerme
authors.affiliation: CEA Nuclear Energy Division, Radiochemistry & Processes Department, Marcoule, F-30207 Bagnols-sur-Cèze, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Couston
authors.affiliation: CEA Nuclear Energy Division, Radiochemistry & Processes Department, Marcoule, F-30207 Bagnols-sur-Cèze, France.
authors.forename: Alastair
authors.initials: A
authors.lastname: Magnaldo
authors.affiliation: Université de Lyon, Institut des Sciences Analytiques, UMR 5280, CNRS, Université Lyon 1, ENS Lyon - 5, rue de la Doua, F-69100 Villeurbanne, France. Electronic address: vincent.dugas@univ-lyon1.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Dugas
keywords: Actinide analysis; Free acidity measurement; Miniaturized analysis; Sequential injection analysis; Uranium