J. Sep. Sci. 2013, 36, 3411–3418 3411 Bruno M. Soares 1 Ederson R. Pereira 1 Juliana V. Maciel 1 Augusto A. Vieira 1 Fabio A. Duarte 1,2 1 Escola de Qu´ ımica e Alimentos, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil 2 Departamento de Qu´ ımica, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil Received June 5, 2013 Revised July 30, 2013 Accepted July 31, 2013 Research Article Assessment of dispersive liquid–liquid microextraction for the simultaneous extraction, preconcentration, and derivatization of Hg 2+ and CH 3 Hg + for further determination by GC–MS This work reports the development of a dispersive liquid–liquid microextraction method for the simultaneous extraction, preconcentration, and derivatization of Hg 2+ and CH 3 Hg + species from water samples for further determination by GC–MS. Some parameters of the proposed method, such as volume and type of disperser and extraction solvent, and Na[B(C 6 H 5 ) 4 ] concentration were investigated using response surface methodology. Suitable recoveries were obtained using 80 LC 2 Cl 4 (as extraction solvent), 1000 L ethanol (as disperser solvent), and 300 L 2.1 mmol/L Na[B(C 6 H 5 ) 4 ] (as derivatizing agent). Accuracy was evaluated in terms of recovery and ranged from 87 to 99% with RSD values <7%. In addition, a certified reference material of water (NIST 1641d) was analyzed and agreed with the certified value about 107% (for Hg 2+ ), with RSD values <8.5%. LODs were 0.3 and 0.2 g/L, with enrichment factors of 112 and 115 for Hg 2+ and CH 3 Hg + , respectively. The optimized method was applied for the determination of Hg 2+ and CH 3 Hg + in tap, well, and lake water samples. Keywords: GC-MS / Mercury speciation / Microextraction / Water samples DOI 10.1002/jssc.201300599  Additional supporting information may be found in the online version of this article at the publisher’s web-site 1 Introduction Mercury is a toxic and nonessential element for humans. Among the elements most studied in the context of speciation analysis, mercury stands out because it is one of the most harmful toxic elements in respect to environmental pollution [1]. In humans, the methylmercury (CH 3 Hg + ) species can be easily absorbed by the gastrointestinal tract and concentrate in the central nervous system [2,3]. In general, organic species are more toxic than the inorganic species; in natural water, inorganic mercury (Hg 2+ ) and CH 3 Hg + are the main species [1, 4]. Correspondence: Dr. Fabio A. Duarte, Departamento de Qu´ ımica, Universidade Federal de Santa Maria, Av. Roraima, 1000, Bairro Camobi, Santa Maria-RS, 97105900, Brazil E-mail: fabioand@gmail.com Fax: +55-55-32209445 Abbreviations: C D , concentration of derivatizing agent; CPE, cloud-point extraction; CRM, certified reference material; DLLME, dispersive liquid–liquid microextraction; ICP-MS, in- ductively coupled plasma mass spectrometry; DAD, diode array detection; ICP-MS, inductively coupled plasma mass spectrometry; R ino , recovery for Hg 2+ species; R org , recovery for CH 3 Hg + species; S D , disperser solvent; SDME, single drop microextraction; V ES , volume of extraction solvent The main analytical techniques used for mercury species determination are based on the use of hyphenated tech- niques, which requires the coupling between a separation system and a specific detector [5–8]. LC coupled to induc- tively coupled plasma mass spectrometry (ICP-MS) has been widely reported for mercury speciation, with some advan- tages, such as high sensitivity and no need of a derivatization step [9–11]. The use of GC as a separation system coupled to ICP-MS [12, 13], atomic fluorescence spectroscopy [14, 15], and MS [13,16–20] has also been employed for mercury speci- ation. However, equipment such as an ICP-MS is not readily available in many laboratories because of the relatively high cost. When compared with LC, GC shows advantages, such as the quantitative elution of analytes, avoiding the nebulization step, which consequently improves the LOD [21]. The GC–MS technique can be considered an alternative for the determination of mercury species in water samples when a preconcentration step is previously used. Thus, there are some methods for extraction and preconcentration of mer- cury species, such as solid-phase microextraction [17, 18], stir bar sorptive extraction [19, 22], single-drop microextraction (SDME) [23], and cloud-point extraction (CPE) [24], which have shown high enrichment factors. However, some of these methods (e.g., solid-phase microextraction and stir bar sorptive extraction) usually require systems with thermal C  2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com