Flame atomic absorption spectrometric determination of cobalt in biological materials using a flow-injection system with on-line preconcentration by ion-pair adsorption

Traces of cobalt in biological materials were determined by flow-injection flame atomic absorption spectrometry. The analyte was preconcentrated and separated from the bulk of the matrix by on-line ion-pair adsorption of the cobalt-nitroso-R salt complex in the presence of tetrabutylammonium bromide as a counter-ion reagent in a flow-injection system. The ion-pair was collected on an on-line C18 micro-column and eluted by ethanol directly into the nebulizer-burner system of an atomic absorption spectrometer. The interference from iron was masked by merging a sodium citrate solution to the sample flow. An enhancement factor of 40 and a sampling frequency of 45 h−1 were obtained for a collecting time of 60 s. The detection limit (3σ) in the sample digest was 3 μg l−1. The relative standard deviation at the 50 μg l−1 cobalt level was 2.4%. The analytical results obtained for standard reference biological material were in good agreement with the certified or reference values.