Cold vapor-solid phase microextraction using amalgamation in different Pd-based substrates combined with direct thermal desorption in a modified absorption cell for the determination of Hg by atomic absorption spectrometry Vanesa Romero, Isabel Costas-Mora, Isela Lavilla, Carlos Bendicho ⁎ Departamento de Química Analítica y Alimentaria, Área de Química Analítica; Facultad de Química, Universidad de Vigo, Campus As Lagoas-Marcosende s/n, 36310 Vigo, Spain abstract article info Article history: Received 11 November 2010 Accepted 25 January 2011 Available online 31 January 2011 Keywords: Hg preconcentration SPME Pd-based substrates Cold vapor Modified absorption cell AAS In this work, different Pd-based substrates (i.e. Pd wire, Pd-coated stainless steel wire and Pd-coated SiO 2 ) are tried for microextraction of Hg prior to its release into a modified quartz T-cell so as to develop a cost- effective, sensitive and easy-to-handle coupling between solid-phase microextraction (SPME) and atomic absorption spectrometry. The new design allows a direct sample injection from the SPME device into a quartz T-cell thus avoiding analyte dilution. Mercury amalgamation onto a Pd wire provided the best performance in respect to sensitivity and fiber lifetime, but Pd wires could not be implemented in the SPME device due to their poor mechanical characteristics. On the contrary, Pd-coated SiO 2 fibers could be easily adapted to the typical sampling device used for SPME. Narrow time-dependent absorption signal profiles that could be integrated within 25 s were obtained. The detection limit was 90 pg mL -1 of Hg, and the repeatability expressed as relative standard deviation was 4.3%. © 2011 Elsevier B.V. All rights reserved. 1. Introduction In the last years, miniaturized and solventless sample preparation techniques such as solid phase microextraction (SPME) [1] have received an increasing attention. SPME was introduced by Pawliszyn in the early 1990s [2], being since then, increasingly used for sample preparation [3–5]. SPME is based on the partitioning of analytes between a coated fiber and a sample [6]. The microextraction process has two steps, i.e., partitioning of analytes between the coating and the sample matrix and then, desorption of preconcentrated analytes into an analytical instrument [7]. SPME has several advantages over traditional extraction methods. It is rapid, simple, solvent free, sensitive, and compatible with analyte separation and detection by different techniques. It is small in size and therefore convenient for designing portable devices that can be used in field analysis [8–13]. On the other hand, one of the main drawbacks of the technique is the limited range of coatings that are commercially available and other potential drawbacks such as instability and swelling in organic solvents (which greatly restricted its use in High Performance Liquid Chromatography), breakage of the fiber, stripping of coatings or bending of the needle [13]. Advances in SPME methodology are focused on solving these problems with the development of new coatings having higher extraction efficiencies, selectivity, and stability [14]. In recent years, new extraction phases have been developed such as titanium wire [15], titanium coated copper wire [16], PbO 2 coated platinum wire [17], latex functionalized with ammonium groups [18] or silica functionalized with amino groups [19]. Although solid-phase microextraction was initially applied for the analysis of organic compounds in different samples, this technique can also be applied to inorganic analysis. Different procedures have been developed for the determination of organometallic and inorganic compounds of tin, mercury, selenium, arsenic, lead, manganese and other metals [20–31]. Mercury is one of the most toxic elements impacting on human and ecosystem health and therefore is one of the most studied environmental pollutants. There are three main forms of mercury, namely, elemental mercury, inorganic mercury and organic mercury. Conversion between different forms of mercury results in its distribution in the environment. Major routes of exposition/absorp- tion of mercury for humans are the respiratory system and diet. Different species of mercury have adverse effects on microorganisms, aquatic plants, aquatic invertebrates, fish, marine mammals, birds, plants, invertebrates and humans [32]. Considering the high toxicity of mercury and its wide distribution in the biosphere, analytical procedures providing high sensitivity for the determination of this pollutant have been developed. Studies performed on the determination of mercury using SPME for preconcentration generally have relied on fibers such as polydimethylsiloxane [33–39], polydimethylsiloxane/divinylbenzene [33] or carboxen/polydimethylsiloxane [39]. Spectrochimica Acta Part B 66 (2011) 156–162 ⁎ Corresponding author. Tel.: + 34 986 812281; fax: + 34 986 812556. E-mail address: bendicho@uvigo.es (C. Bendicho). 0584-8547/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2011.01.005 Contents lists available at ScienceDirect Spectrochimica Acta Part B journal homepage: www.elsevier.com/locate/sab