A unified HPLC-ESI-HRMS approach for the quantitative analysis of four aminopolycarboxylic acids and gluconic acid in...

Several chelating agents have been employed throughout decontamination processes in nuclear industry, EDTA (ethylenediaminetetraacetic acid) being the most abundantly used. The presence of these molecules in radioactive waste can affect the mobility of radionuclides and metals in environment during the long-term storage of the nuclear waste. This is why the quantification of certain chelating agents is required during nuclear waste management. The studied samples to be analysed present numerous challenges that require careful sample preparation before their measurement. In this paper, we describe how, based on a previous protocol for the quantification of EDTA, a novel unified method was developed for the simultaneous quantification of four aminopolycarboxylic acid (EDTA, NTA, DTPA and TTHA), and gluconic acid. Suspended solids present in the samples were eliminated by filtration, then the sample was basified to ensure precipitation of remaining metallic ions and their removal. Finally, an excess of Ni²⁺ was added to form complexes with the majority of the analytes. Speciation modelling studies predicted dominant anionic complexes with nickel for the aminopolycarboxylic acid family while gluconic acid remained under its free gluconate form. As experimentally demonstrated, the five anionic species were separated and detected simultaneously in less than 7min through an ion-pair mechanism using an HPLC-ESI-HRMS system. Lastly, the limits of quantification were validated between 2.5 and 6.25mg/L for all chelating agents in sludges.