On-line preconcentration of cobalt in drinking water using a minicolumn packed with activated carbon coupled to electrothermal atomic absorption spectrometric determination

An on-line flow injection preconcentration-electrothermal atomic absorption spectrometry method is developed for trace determination of cobalt in drinking water samples by sorption on a conical minicolumn packed with activated carbon at pH 9.5. The cobalt was eluted from the minicolumn with 10% (v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10 ml was obtained. The detection limit (DL) value for the preconcentration method proposed was 5 ng l−1. The precision for 10 replicate determinations at the 50 ng l−1 Co level was 4.7% relative standard deviation. The calibration graph using the preconcentration system for cobalt was linear with a correlation coefficient of 0.9993 at levels near the DLs up to at least 0.35 μg l−1. The method was successfully applied to the determination of cobalt in drinking water samples.