Volatilisation of cobalt chelates for their direct introduction in the vapour phase in flame atomic absorption spectrometry

Different cobalt complexes with β-diketones, dithiocarbamates and 8-hydroxyquinoline were evaluated for the direct determination of cobalt by flame atomic absorption spectrometry with vapour-phase sample introduction. The order of sensitivity is Co(Ox)2∼ Co(PDC)3∼ Co(AA)2 < Co(Ox)3 < Co(HFA)2 < Co(DTC)3 < Co(TFA)2, where Ox = 8-hydroxyquinoline, PDC = tetramethylenedithiocarbamate (pyrrolidinedithiocarbamate), AA = acetylacetone, HFA = hexafluoroacetylacetone, DTC = diethyldithiocarbamate and TFA = trifluoroacetylacetone. The sensitivity of Co(TFA)2 expressed as the slope of the calibration graph is 0.502 ng–1, with a reproducibility varying between 0.6 and 2.5%(relative standard deviation). Two simple volatilisation systems that can be adapted to conventional instrumentation, have been designed. The most sensitive method was applied to determine cobalt in steel, bronze and brass, with good results.