Automated determination of uranium(VI) at ultra trace levels exploiting flow techniques and spectrophotometric detection using a liquid waveguide capillary cell

Rapid and fully automated multisyringe flow-injection analysis (MSFIA) with a multi-pumping flow system (MPFS) coupled to a long path-length liquid waveguide capillary cell (LWCC) is proposed for the determination of uranium(VI) at ultra trace levels. On-line separation and pre-concentration of uranium is carried out by means of a TRU resin. After elution, uranium(VI) is spectrophotometrically detected after reaction with arsenazo-III. Combination of the MSFIA and MPFS techniques with the TRU-resin enables the analysis to be performed in a short time, using large sample volumes and achieving high selectivity and sensitivity levels. A detection limit of 12.6 ng L⁻¹ (ppt) is reached for a 100-mL sample volume. The versatility of the proposed method also enables pre-concentration of variable sample volumes, enabling application of the analysis to a wide concentration range. Reproducibility of better than 5% and a resin durability of 40 injections should be emphasized. The developed method was successfully applied to different types of environmental sample matrices with recoveries between 95 and 108%.