DETERMINATION OF COBALT IN BIOLOGICAL SAMPLES BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY AFTER PRECONCENTRATION BY EXTRACTION WITH 1,5-BIS (DI-2-PYRIDYLMETHYLENE)THOIOCARBONHYDRAZIDE

A method is proposed for the solvent extraction of cobalt using 1,5-bi s(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) as extractant. Th e optimum extraction conditions were evaluated from a critical study o f the effect of pH, concentration of extractant, shaking time and ioni c strength. The maximum volume ratio of the aqueous to organic phase w as 30:1 for a single-stage extraction of 99-100 % of the metal ion. Th e detection limit is 0.9 ng/ml cobalt, and the calibration is linear f rom 0.9 to 1000 ng/ml. The effect of interferences was studied and no interferences from the elements commonly found in biological materials were observed. The extraction method was applied to the determination of cobalt in some biological materials using inductively coupled plas ma atomic emission spectrometry (ICP-AES).