FLAME ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF COBALT IN BIOLOGICAL-MATERIALS USING A FLOW-INJECTION SYSTEM WITH ONLINE PRECONCENTRATION BY ION-PAIR ADSORPTION

Traces of cobalt in biological materials were determined by now-inject ion flame atomic absorption spectrometry. The analyte was preconcentra ted and separated from the bulk of the matrix by on-line ion-pair adso rption of the cobalt-nitroso-R salt complex in the presence of tetrabu tylammonium bromide as a counter-ion reagent in a flow-injection syste m. The ion-pair was collected on an on-line C-18 micro-column and elut ed by ethanol directly into the nebulizer-burner system of an atomic a bsorption spectrometer. The interference from iron was masked by mergi ng a sodium citrate solution to the sample now. An enhancement factor of 40 and a sampling frequency of 45 h(-1) were obtained for a collect ing time of 60 s. The detection limit (3 sigma) in the sample digest w as 3 mu g l(-1). The relative standard deviation at the 50 mu g l(-1) cobalt level was 2.4%. The analytical results obtained for standard re ference biological material were in good agreement with the certified or reference values.