title: Response surface methodology based on central composite design as a chemometric tool for optimization of dispersive-solidification liquid-liquid microextraction for speciation of inorganic arsenic in environmental water samples.
abstract: Dispersive-solidification liquid-liquid microextraction (DSLLME) coupled with electrothermal atomic absorption spectrometry (ETAAS) was developed for preconcentration and determination of inorganic arsenic (III, V) in water samples. At pH=1, As(III) formed complex with ammonium pyrrolidine dithiocarbamate (APDC) and extracted into the fine droplets of 1-dodecanol (extraction solvent) which were dispersed with ethanol (disperser solvent) into the water sample solution. After extraction, the organic phase was separated by centrifugation, and was solidified by transferring into an ice bath. The solidified solvent was transferred to a conical vial and melted quickly at room temperature. As(III) was determined in the melted organic phase while As(V) remained in the aqueous layer. Total inorganic As was determined after the reduction of the pentavalent forms of arsenic with sodium thiosulphate and potassium iodide. As(V) was calculated by difference between the concentration of total inorganic As and As(III). The variable of interest in the DSLLME method, such as the volume of extraction solvent and disperser solvent, pH, concentration of APDC (chelating agent), extraction time and salt effect, was optimized with the aid of chemometric approaches. First, in screening experiments, fractional factorial design (FFD) was used for selecting the variables which significantly affected the extraction procedure. Afterwards, the significant variables were optimized using response surface methodology (RSM) based on central composite design (CCD). In the optimum conditions, the proposed method has been successfully applied to the determination of inorganic arsenic in different environmental water samples and certified reference material (NIST RSM 1643e).
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, P.O. Box 11365-4435, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Asadollahzadeh
authors.affiliation: Faculty of Engineering, Nour Branch, Islamic Azad University, Nour, Iran. Electronic address: ha.tavakoli159@yahoo.com.
authors.forename: Hamed
authors.initials: H
authors.lastname: Tavakoli
authors.affiliation: Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, P.O. Box 11365-8486, Tehran, Iran.
authors.forename: Meisam
authors.initials: M
authors.lastname: Torab-Mostaedi
authors.affiliation: North Drilling Company, Tehran, Iran.
authors.forename: Ghaffar
authors.initials: G
authors.lastname: Hosseini
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, P.O. Box 11365-4435, Tehran, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Hemmati
mesh_terms: D000465:Algorithms; D001151:Arsenic / Q000032:analysis* / Q000302:isolation & purification; D007851:Dodecanol / Q000737:chemistry; D060766:Drinking Water / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods; D006863:Hydrogen-Ion Concentration; D059627:Liquid Phase Microextraction / Q000379:methods*; D011193:Potassium Iodide / Q000737:chemistry; D011759:Pyrrolidines / Q000737:chemistry; D015203:Reproducibility of Results; D045483:Rivers / Q000737:chemistry; D012623:Seawater / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013054:Spectrophotometry, Atomic / Q000379:methods*; D013859:Thiocarbamates / Q000737:chemistry; D013885:Thiosulfates / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000302:isolation & purification; D014881:Water Supply / Q000032:analysis
chemical_list: D060766:Drinking Water; D011759:Pyrrolidines; D012997:Solvents; D013859:Thiocarbamates; D013885:Thiosulfates; D014874:Water Pollutants, Chemical; D007851:Dodecanol; D011193:Potassium Iodide; C020972:pyrrolidine dithiocarbamic acid; C017717:sodium thiosulfate; D001151:Arsenic
keywords: Central composite design; Dispersive-solidification liquid–liquid microextraction; Environmental water samples; Inorganic arsenic; Response surface methodology