Preconcentration and determination of low amounts of cobalt in black tea, paprika and marjoram using dispersive liquid-liquid microextraction and flame atomic absorption spectrometry

A dispersive liquid-liquid microextraction (DLLME) method for separation/preconcentration of ultra trace amounts of Co(II) and its determination with FAAS was developed. The DLLME behavior of Co(II) using Aliquat 336-chloride as ion pairing agent was systematically investigated. The factors influencing the ion pair formation and extraction by DLLME method were optimized. Under the optimized conditions for 150 mu L of extraction solvent (carbon tetrachloride), 1.5 mL disperser solvent (acetonitrile) and 5 mL of sample, the enrichment factor was 30. The detection limit was 5.6 mu g L-1 and the RSD for replicate measurements of 1 mg L-1 was 1.32 %. The calibration graph using the preconcentration system for cobalt was linear from 40 to 400 mu g L-1 with a correlation coefficient of 0.999. The proposed method was successfully applied for determination of cobalt in black tea, paprika and marjoram real samples.