title: Simultaneous preconcentration of copper, zinc, cadmium, and nickel in water samples by cloud point extraction using 4-(2-pyridylazo)-resorcinol and their determination by inductively coupled plasma optic emission spectrometry.
abstract: A procedure for simultaneous separation/preconcentration of copper, zinc, cadmium, and nickel in water samples, based on cloud point extraction (CPE) as a prior step to their determination by inductively coupled plasma optic emission spectrometry (ICP-OES), has been developed. The analytes reacted with 4-(2-pyridylazo)-resorcinol (PAR) at pH 5 to form hydrophobic chelates, which were separated and preconcentrated in a surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114). The parameters affecting the extraction efficiency of the proposed method, such as sample pH, complexing agent concentration, buffer amount, surfactant concentration, temperature, kinetics of complexation reaction, and incubation time were optimized and their respective values were 5, 0.6 mmol L(-1), 0.3 mL, 0.15% (w/v), 50 degrees C, 40 min, and 10 min for 15 mL of preconcentrated solution. The method presented precision (R.S.D.) between 1.3% and 2.6% (n=9). The concentration factors with and without dilution of the surfactant-rich phase for the analytes ranged from 9.4 to 10.1 and from 94.0 to 100.1, respectively. The limits of detection (L.O.D.) obtained for copper, zinc, cadmium, and nickel were 1.2, 1.1, 1.0, and 6.3 microg L(-1), respectively. The accuracy of the procedure was evaluated through recovery experiments on aqueous samples.
authors: Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CP 96, 13416-000 Piracicaba, SP, Brazil.
authors: Edson Luiz
authors: EL
authors: Silva
authors: Paulo dos Santos
authors: Pdos S
authors: Roldan
authors: Maria Fernanda
authors: MF
authors: Giné
mesh_terms: D002021:Buffers; D002104:Cadmium / Q000302:isolation & purification*; D002863:Chromogenic Compounds / Q000737:chemistry*; D003300:Copper / Q000302:isolation & purification*; D003902:Detergents / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000302:isolation & purification*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D012118:Resorcinols / Q000737:chemistry*; D012996:Solutions; D013057:Spectrum Analysis / Q000379:methods; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D015032:Zinc / Q000302:isolation & purification*
chemical_list: D002021:Buffers; D002863:Chromogenic Compounds; D003902:Detergents; D012118:Resorcinols; D012996:Solutions; D014874:Water Pollutants, Chemical; D002104:Cadmium; D014867:Water; D011092:Polyethylene Glycols; D003300:Copper; D009532:Nickel; D017830:Octoxynol; C010615:Nonidet P-40; D015032:Zinc; C028398:4-(2-pyridylazo)resorcinol