CLOUD POINT EXTRACTION FOR COBALT PRECONCENTRATION WITH ON-LINE PHASE SEPARATION IN A KNOTTED REACTOR FOLLOWED BY ETAAS DETERMINATION IN DRINKING WATERS

RAÚL A. GIL, JOSÉ A. GÁSQUEZ, ROBERTO OLSINA, LUIS D. MARTINEZA, SOLEDAD CERUTTI

TALANTA

Elsevier

Año: 2008

0039-9140

A novel method for cobalt preconcentration by cloud point extraction with online 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 nonionic 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 (RSD), 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.