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

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

TALANTA

Elsevier

Lugar: London; Año: 2008 vol. 76 p. 669 - 673

0039-9140

A novel method for cobalt preconcentration by cloud point extraction with on-line phase separationin 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). Thesurfactant rich-phase was removed from the knotted reactor with 75L of methanol acidified with0.8 mol L−1 nitric acid, directly into the dosing hole of the L’Vov graphite tube. An enrichment factor of 15was 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 samplesolutionwas 10 ng L−1. The precision, expressed as the relative standard deviation (R.S.D.), for 10 replicatedeterminations at 0.5gL−1 Co level was 4.5%. Verification of the accuracy was carried out by analysisof a standard reference material (NIST SRM 1640e “Trace elements in natural water”). The method wassuccessfully applied to the determination of cobalt in drinking water samples.