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 syner gistic action of thenoyltrifluoroacetone (TTA) and dibenzo-24-crown-8 (DB24 C8) in o-dichlorobenzene combined with graphite furnace atomic absorption s pectrophotometry. The composition of the resulting adduct was determined by slope analysis revealing a stoichiometric formula of Co(TTA)(2)DB24C8 with a stability constant (log beta) of 5.51. Calibration plots of cobalt (II) gave linear responses (r(2) = 0.999) with increasing concentration of the s tandards in the ng/mL range. The detection limit was 0.015 ng/mL. The analy tical precision was less than 4% (RSD), and the spike recoveries of cobalt (II) was greater than or equal to 89% for the preconcentration factors up t o 20-fold. The method was applied to the determination of the cobalt conten t in Kakehashi river (Komatsu City), Japan Sea (Uchinada Town) and tap wate r (Kanazawa University) samples and the results were found to be 5.82+/-0.7 3 ng/mL, 0.097+/-0.010 and < 0.015 ng/mL, respectively.