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

Abstract

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 µL 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 µg 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 µg 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.