Integrating natural deep eutectic solvents and ionic liquids as green mobile phase additives for enhanced selenium...

A study to evaluate the effects of natural deep eutectic solvent (NADES) and ionic liquids (ILs) on the separation of selenium (Se) species by reversed phase high performance liquid chromatography and detection by hydride generation atomic fluorescence spectrometry (RP-HPLC-HG-AFS) was performed in this work. The NADESs choline chloride:ethylene glycol and choline chloride:glycerol were applied as mobile phase additives for the separation of Se(IV), Se(VI), selenomethionine (SeMet) and Se-methylselenocysteine (SeMetSeCys). The effects of NADES composition, molar ratio, and concentration on chromatographic performance were systematically investigated, along with the influence of pH, buffer strength, and flow rate. The combined use of NADESs with the IL 1-hexyl-3-methylimidazolium chloride ([C₆mim]Cl) significantly enhanced the resolution of inorganic Se species. In addition, the effects of NADES and IL on the Se fluorescence signals obtained with the HG-AFS techniques were also studied using a multivariate technique for sensitivity optimization. The method achieved limits of detection of 1.59-2.78 µg L^-1, with relative standard deviations of 0.53-1.86 % for retention times and 1.23-1.72 % for peak areas. Finally, the proposed analytical method was successfully applied to Se speciation analysis in complex food samples, including nuts and Se-enriched garlic, yielding recoveries of 93.4-106 %.