title: Cloud point extraction for cobalt preconcentration with on-line phase separation in a knotted reactor followed by ETAAS determination in drinking waters.
abstract: 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 microL 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 microg 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.
authors.affiliation: Area de Química Analítica, Facultad de Química Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, San Luis, C.P. 5700, Argentina.
authors.forename: Raúl A
authors.initials: RA
authors.lastname: Gil
authors.forename: José A
authors.initials: JA
authors.lastname: Gásquez
authors.forename: Roberto
authors.initials: R
authors.lastname: Olsina
authors.forename: Luis D
authors.initials: LD
authors.lastname: Martinez
authors.forename: Soledad
authors.initials: S
authors.lastname: Cerutti
mesh_terms: D003035:Cobalt / Q000032:analysis*; D008823:Micelles; D013054:Spectrophotometry, Atomic / Q000379:methods* / Q000592:standards; D013501:Surface-Active Agents; D014873:Water Pollutants / Q000032:analysis*; D014881:Water Supply / Q000032:analysis
chemical_list: D008823:Micelles; D013501:Surface-Active Agents; D014873:Water Pollutants; D003035:Cobalt