Effectiveness of fullerene as a sorbent for the determination of trace amounts of cobalt in wheat flour by electrothermal atomic absorption spectrometry

Abstract

A flow injection system for the on-line preconcentration of ultratrace levels of cobalt by sorption with ammonium pyrrolidinedithiocarbamate on a C ₆₀ fullerene column was developed. The eluate volume is reduced and dispersion minimized by using a nitrogen (or air) stream to carry the eluent (IBMK) for elution of the adsorbed chelate, which is collected in a 500 µl PTFE autosampler cup. The analytical figures of merit for the determination of cobalt are as follows: limit of detection (3σ), 8 ng l ^–1 ; precision (RSD), 4% for 0.2 ng ml ^–1 ; preconcentration factor, 40 (using 25 ml of sample and 500 µl of IBMK). Similar experiments involving C ₁₈ -bonded silica as sorbent revealed ethanol to be the most suitable eluent under these conditions. The results obtained in the determination of cobalt in wheat flour testify to the usefulness of the proposed method.