Cloud point extraction for cobalt preconcentration with on-line phase separation in a knotted reactor followed by ETAAS determination in drinking waters

R.A. GIL, J.A. GÁSQUEZ, R. OLSINA, L.D. MARTINEZ, S. CERUTTI

TALANTA

Elsevier

Año: 2008 vol. 76 p. 669 - 673

0039-9140

A novel method for cobalt preconcentration by cloud point extraction with on-line phase separation in a PTFE knotted reactor and further determination by electrothermal atomic absorption spectrometry (ETAAS) is proposed. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmonop-nonylphenylether (PONPE 7.5) and it was retained on the inner walls of a knotted reactor (KR). The surfactant rich-phase was removed from the knotted reactor with 75uL of methanol acidified with 0.8 mol L−1 nitric acid, directly into the dosing hole of the L’Vov graphite tube. An enrichment factor of 15 was obtained with a preconcentration time of 60 s, with respect to the direct determination of cobalt byETAAS in aqueous solutions. The value of the detection limit for the preconcentration of 5mL of sample solutionwas 10 ng L−1. The precision, expressed as the relative standard deviation (R.S.D.), for 10 replicate determinations at 0.5 ugL−1 Co level was 4.5%. Verification of the accuracy was carried out by analysis of a standard reference material (NIST SRM 1640e “Trace elements in natural water”). The method was successfully applied to the determination of cobalt in drinking water samples.