Preconcentration and determination of nickel (II) and copper (II) ions, in vegetable oils by [TBP] [PO4] IL-based dispersive liquid-liquid microextraction technique, and flame atomic absorption spectrophotometry

The present research is a novel enrichment method based on ionic liquid dispersive liquid-liquid micro-extraction that was combined with flame atomic absorption spectroscopy to determine the concentration of Cu2+ and Ni2+ ions in vegetable oil samples at trace levels. The ionic liquid [TBP] [PO4] and chloroform were used as the extraction and dispersive solvent respectively. Canola oil containing oil-soluble standard of Cu2+ or Ni2+ ions as the model compound was used. Under optimum conditions the linear ranges were 1-100 and 1 - 200 mu g/kg for Cu2+ and Ni2+ respectively with correlation coefficient (R-2) of 0.99. The relative standard deviation (RSD, n = 5) for Cu2+ and Ni2+ at a concentration of 20 mu g/kg was 2.2 % and 3.2 % respectively. The LOD (3 s) and LOQ (10 s) were 0.35 ppb and 1.2 ppb; and 0.77 ppb and 2.57 ppb for Cu2+ and Ni2+ respectively.