WUILLOUD Rodolfo German
congresos y reuniones científicas
Simultaneous determination of selenium and tellurium species in environmental samples by on-line ionic liquid based in-situ solvent formation microextraction with atomic fluorescence spectrometry detection
Congreso; LatinXChem (Congreso de Química en Twitter); 2020
Institución organizadora:
Cinvestav Unidad Mérida
A novel on-line preconcentration and speciation analysis method for the simultaneous determination of inorganic Se and Te species has been developed in this work. The methodology is based on the on-line formation of a hydrophobic ionic liquid (IL) directly in the liquid sample stream of a flow injection system, thus achieving an efficient and rapid extraction of Se(IV) and Te(IV) complexed with ammonium pyrrolidine dithiocarbamate into the finely dispersed extractant droplets, that were then retained with a cotton-filled column. A full study of the chemical and hydrodynamical parameters was developed, including the right selection of the IL used as extractant and its concentration, pH, complexing reagent, sample and ion-exchange reagent volumes and column design. The treatment of a second pre-reduced aliquot allowed for the determination of the total Se and Te concentration, from which the concentrations of the Se(VI) and Te(VI) species were calculated by difference. Additionally, a miniaturized external hydride generator was adapted to the spectrometer in order to increase the sensitivity of the atomic fluorescence measurements using only 250 μL of 5 mol L−1 HNO3 in methanol as eluent. The analytical figures of merit obtained for 15 mL of sample included sensitivity enhancement factors of 71, 70, 49 and 40 for Te(IV), Te(VI), Se(IV) and Se(VI), respectively, and limits of detection of 1.8 ng L−1 for both Te species, 2.6 ng L−1 for Se(IV) and 3.2 ng L−1 for Se(VI). After optimization, the method was successfully applied for the analysis of environmental samples: soils and sediments, as well as sea, river, underground and tap water.