DETERMINATION OF TRACE AMOUNTS OF COBALT BY FLOW-INJECTION WITH SPECTROPHOTOMETRIC DETECTION

A flow injection system incorporating a microcolumn with modified alumina was used in conjunction with spectrophotometric detection at 520 nm for the preconcentration and determination of cobalt. The analyte was preconcentrated on-line as the cobalt-nitroso-R-salt complex during the sampling stage and elution was effected by injection of sodium hydroxide solution. The limit of detection for a 10 min preconcentration time was 3.5 ng ml(-1) and the relative standard deviation at the 20 ng ml(-1) level was 3.1%, No significant interferences due to the presence of several metal ions was found. The procedure was applied to the determination of cobalt in oriental tobacco leaves and pyrite ore certified reference materials.