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

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

TALANTA

ELSEVIER BV

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 polyethyleneglycolmono-p-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 75 μL 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 by ETAAS in aqueous solutions. The value of the detection limit for the preconcentration of 5 mL of sample solution was 10 ng L-1. The precision, expressed as the relative standard deviation (R.S.D.), for 10 replicate determinations at 0.5 μg L-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. © 2008 Elsevier B.V. All rights reserved