Journal of Applied Chemical Science International

In this study, an efficient and simple pre-concentration procedure was proposed for the determination of chromium (VI) ions in water samples. A hydrophobic ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate or in brief [C₈MIM] [PF₆]) was used as extractant solvent. This ionic liquid (IL) was  chosen  among  the  other  counterparts  considering  its  high  hydrophobicity,  which  facilitates complete separation of it from the aqueous phase. Dispersion of [C₈MIM] [PF₆] in aqueous phase was made just by controlling the temperature at its optimum value, without using an organic dispersant solvent.  At  first,  chromium  (VI)  was  complexed  with  ammonium  pyrrolidine  dithiocarbamate (APDC) as a chelating agent, then a very small amount of [C₈MIM] [PF₆] was dispersed in water sample at optimum temperature, instantly the complex of Cr (VI)-APDC was extracted into the fine droplets of ionic liquid phase. Determination step was made using a high resolution continuum-source flame atomic absorption spectrometer. Some important parameters such as temperature, volume of chelating agent, pH, amount of ionic liquid, centrifugation time and rate were investigated.  Under optimum conditions, the calibration graph was linear (R = 0.9975) in the range of 0.04 to 2.0 μg mLˉ. The limit of detection (3σ) of the proposed method was 0.01 μg mLˉ and the relative standard deviation for seven replicated determinations of 1.0 μg mLˉ Cr (VI) was 1.03%.