title: Thermospray flame furnace-AAS determination of copper after on-line sorbent preconcentration using a system optimized by experimental designs.
abstract: The present paper describes the on-line coupling of a flow-injection system to a new technique, thermospray flame furnace-AAS (TS-FF-AAS), for the preconcentration and determination of copper in water samples. Copper was preconcentrated onto polyurethane foam (PUF) complexed with ammonium O,O-diethyldithiophosphate (DDTP), while elution was performed using 80% (v/v) ethanol. An experimental design for optimizing the copper preconcentration system was established using a full factorial (2(4)) design without replicates for screening and a Doehlert design for optimization, studying four variables: sample pH, ammonium O,O-diethyldithiophosphate (DDTP) concentration, presence of a coil and the sampling flow rate. The results obtained from the full factorial and based on a Pareto chart indicate that only the pH and the DDTP concentration, as well as their interaction, exert influence on the system within a 95% confidence level. The proposed method provided a preconcentration factor of 65 fold, thus notably improving the detectability of TS-FF-AAS. The detection limit was 0.22 microg/dm3 and the precision, expressed as the relative standard deviation (RSD) for eight independent determinations, was 2.7 and 1.1 for copper solutions containing 5 and 30 microg/dm3, respectively. The procedure was successfully applied for copper determination in water samples.
authors.affiliation: Departamento de Cîencias Exatas, Universidade Federal de Alfenas (Unifal-MG), Minas Gerais, Brazil. ctarley@bol.com.br
authors.forename: César Ricardo Teixeira
authors.initials: CR
authors.lastname: Tarley
authors.forename: Eduardo da Costa
authors.initials: Eda C
authors.lastname: Figueiredo
authors.forename: Geraldo Domingues
authors.initials: GD
authors.lastname: Matos
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000704:Analysis of Variance; D002244:Carbon / Q000737:chemistry; D002413:Cations, Divalent / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry; D003300:Copper / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D015999:Multivariate Analysis; D063086:Organothiophosphates / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D015203:Reproducibility of Results; D013054:Spectrophotometry, Atomic / Q000295:instrumentation / Q000379:methods*; D014867:Water / Q000032:analysis*
chemical_list: D002413:Cations, Divalent; D002614:Chelating Agents; D063086:Organothiophosphates; D011140:Polyurethanes; D014867:Water; C059015:O,O-diethyl dithiophosphate; D002244:Carbon; D003300:Copper; C028279:polyurethane foam; D000537:Aluminum Oxide