Cobalt ultra-trace on-line preconcentration and determination using a PTFE turnings packed column and electrothermal atomic absorption spectrometry. Applications in natural waters and biological samples

Abstract

A novel flow injection (FI) on-line column preconcentration system, coupled to electrothermal atomic absorption spectrometry (ETAAS) for ultra-trace cobalt determination, has been developed. Polytetrafluoroethylene (PTFE) turnings are used as sorbent material. The sample is mixed on-line with ammonium pyrrolidine dithiocarbamate (APDC) and the non-charged Co^II–PDC complex is retained on the hydrophobic PTFE turnings at a pH range of 5.5–7.0. The preconcentrated complex is effectively eluted with a discrete zone of 35 µl isobutyl methyl ketone (IBMK). Airflow is used to introduce the eluent into the transversely heated graphite tube atomizer, through the column. With 60 s preconcentration time and 11.5 ml min⁻¹ sample flow rate the enhancement factor is 87 and the sample frequency is 20 h⁻¹. The detection limit is c_L = 4 ng l⁻¹, the relative standard deviation is 4.5% at the 0.1 µg l⁻¹ level and the calibration curve is linear over the concentration range 0.01–0.25 µg l⁻¹. The proposed method was evaluated by analyzing certified reference materials of water and mussel tissue. Finally, it was successfully applied to the analysis of natural waters and biological samples.