Preconcentration and Determination of Traces of Cobalt(II) as a Thenoyltrifluoroacetone Complex with Dibenzo-24-Crown-8 by Synergistic Extraction and Graphite Furnace Atomic Absorption Spectrophotometry

A new solvent extraction technique for the enrichment and determination of traces of cobalt (II) in natural waters was developed by means of the synergistic action of thenoyltrifluoroacetone (TTA) and dibenzo-24-crown-8 (DB24C8) in o-dichlorobenzene combined with graphite furnace atomic absorption spectrophotometry. The composition of the resulting adduct was determined by slope analysis revealing a stoichiometric formula of Co(TTA)2DB24C8 with a stability constant (log β) of 5.51. Calibration plots of cobalt (II) gave linear responses (r2 = 0.999) with increasing concentration of the standards in the ng/mL range. The detection limit was 0.015 ng/mL. The analytical precision was less than 4% (RSD), and the spike recoveries of cobalt (II) was ≥ 89% for the preconcentration factors up to 20-fold. The method was applied to the determination of the cobalt content in Kakehashi river (Komatsu City), Japan Sea (Uchinada Town) and tap water (Kanazawa University) samples and the results were found to be 5.82±0.73 ng/mL, 0.097±0.010 and < 0.015 ng/mL, respectively