Determination of cobalt in biological samples by electrothermal atomic absorption spectrometry after extraction with 1,5-bis (di-2-pyridylmethylene) thiocarbohydrazide

A method for the determination of trace amounts of cobalt in biological samples by atomic absorption spectrometry with graphite furnace atomization extraction conditions were evaluated from a critical study of the effects of pH, concentration of extractant, shaking time and ionic strength. The detection limit for cobalt is 0.06 ng ml-1 and the calibration is linear from 0.1 to 2.5 ng ml-1. The relative standard deviation for ten replicate measurements is 1.7 % for 0.5 ng ml-1 of cobalt. The effect of interferences was studied and no interferences from the elements commonly found in biological materials were observed. The chief advantage of the method lies in its maximum allowable aqueous-to-organic phase volume ratio of 30:1. Results from the analysis of some certified biological reference materials are given. (authors). 14 refs., 1 figs., 3 tabs