Speciation of As(III) and As(V) in water samples by graphite furnace atomic absorption spectrometry after solid phase extraction combined with dispersive liquid–liquid microextraction based on the solidification of floating organic drop Mojtaba Shamsipur a,n , Nazir Fattahi a,b,nn , Yaghoub Assadi c , Marzieh Sadeghi a , Kiomars Sharafi b a Department Chemistry, Razi University, Kermanshah, Iran b Research Center for Environmental Determinants of Health (RCEDH), Kermanshah University of Medical Sciences, Kermanshah, Iran c Quality Control Department, Daana Pharmaceutical Company, P.O. Box 501575-5181, Tabriz, Iran article info Article history: Received 22 April 2014 Received in revised form 20 June 2014 Accepted 22 June 2014 Available online 30 June 2014 Keywords: Dispersive liquid–liquid microextraction Solid-phase extraction Graphite furnace atomic absorption spectrometry Arsenic speciation Water analysis abstract A solid phase extraction (SPE) coupled with dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, using diethyldithiphosphate (DDTP) as a proper chelating agent, has been developed as an ultra preconcentration technique for the determina- tion of inorganic arsenic in water samples prior to graphite furnace atomic absorption spectrometry (GFAAS). Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100 mL of As(ΙΙΙ) solution was first concentrated using a solid phase sorbent. The extract was collected in 2.0 mL of acetone and 60.0 mL of 1-undecanol was added into the collecting solvent. The mixture was then injected rapidly into 5.0 mL of pure water for further DLLME-SFO. Total inorganic As(III, V) was extracted similarly after reduction of As(V) to As(III) with potassium iodide and sodium thiosulfate and As(V) concentration was calculated by difference. A mixture of Pd(NO 3 ) 2 and Mg (NO 3 ) 2 was used as a chemical modifier in GFAAS. The analytical characteristics of the method were determined. The calibration graph was linear in the rage of 10–100 ng L 1 with detection limit of 2.5 ng L 1 . Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 80 ng L 1 of As(ΙΙΙ) were 6.8% and 7.5%, respectively. The method was successfully applied to speciation of As(III), As(V) and determination of the total amount of As in water samples and in a certified reference material (NIST RSM 1643e). & 2014 Elsevier B.V. All rights reserved. 1. Introduction The presence of arsenic in drinking water has reached calami- tous proportions in many parts of the world. Arsenic occurs as both inorganic and organic compounds and its toxicity is strongly related to its chemical form. Consequently, it is essential to perform the speciation of this element in aqueous, geological, and biological matrices [1]. Arsenic can be found in drinking water, in the air as volatile arsines, and in soil, where it can concentrate if absorbed on the soil components [2]. The release of arsenic in the environment occurs in a variety of ways through industrial effluents, pesticides, wood preservative agents, combustion of fossil fuels, and mining activity [3]. Exposure to elevated levels of arsenic, as a class I human carcinogen, has become a global concern affecting millions worldwide. The currently recom- mended upper limit of arsenic in drinking water is 10 mgL 1 [4]. This element occurs in the natural environment in four oxidation states: As(V), As(III), As(0) and As(  III). Inorganic compounds consist of water-soluble arsenite, As(III), as the most toxic form, and arsenate, As(V), as the less toxic form, and such pollu- tants have been associated with many health problems such as skin lesions, keratosis (skin hardening), lung cancer, and bladder cancer [3]. Because of very low concentration of arsenic in environmental and biological samples, sensitive analytical techniques are required. Up to now, a number of analytical techniques have been developed Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2014.06.049 0039-9140/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ98 21 66908033; fax: þ98 21 6690803. nn Corresponding author at: Department Chemistry, Razi University, Kermanshah, Iran. Tel.: þ98 831 8262052; fax: þ98 831 8263048. E-mail addresses: mshamsipur@yahoo.com (M. Shamsipur), nazirfatahi@yahoo.com, nazirfatahi@gmail.com (N. Fattahi). Talanta 130 (2014) 26–32