Technical Note Cr speciation in water samples by dispersive liquid–liquid microextraction combined with total reflection X-ray fluorescence spectrometry Z. Bahadir a , V.N. Bulut b , M. Hidalgo c , M. Soylak d , E. Marguí c, ⁎ a Department of Chemistry, Giresun University, Giresun, Turkey b Macka Vocational School, Karadeniz Technical University, Macka, Trabzon, Turkey c Department of Chemistry, Faculty of Sciences, University of Girona, Girona, Spain d Department of Chemistry, Faculty of Sciences, Erciyes University, Kayseri, Turkey abstract article info Article history: Received 9 September 2015 Accepted 9 November 2015 Available online 14 November 2015 Keywords: Total-reflection X-ray fluorescence spectroscopy (TXRF) DLLME Cr species Water sample A novel method based on dispersive liquid–liquid microextraction (DLLME) and total-reflection X-ray fluores- cence spectrometry (TXRF) is proposed for the determination and preconcentration of inorganic Cr species (Cr(VI) and Cr(III)) in water samples. Parameters affecting the extraction procedure for Cr speciation (pH, sample volume, disperser solvent, complexing agent, organic solvent, temperature) and TXRF conditions (sample volume, drying mode, measure- ment time, internal standardization) have been carefully evaluated to ensure the highest sensitivity for Cr deter- mination. It was found that the minimum Cr content that can be detected was 0.8 μgL -1 . This value is significantly lower than the maximum Cr content permissible in drinking waters and it is better or comparable with those obtained in other published works based on the use of solid phase extraction or liquid phase microextraction in combination with atomic absorption spectrometry techniques. A good linearity (R 2 = 0.9937) was obtained in the range of 5 to 4000 μgL -1 demonstrating the suitability of the DLLME + TXRF for both the analysis of drinking and waste water samples. Additional advantages of the DLLME-TXRF systems include the use of very small amount of reagents and the sim- plicity and low cost of operation of the benchtop instrument used (no cooling media and gas consumption are needed). © 2015 Elsevier B.V. All rights reserved. 1. Introduction Cr is an environmental pollutant resulting mainly from industrial activities including electroplating, wood preservation, leather tanning and steel industries [1,2]. The main forms of Cr found in the environ- ment are trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). Cr(III) appears to be one of the essential elements for the prop- er functioning of living organisms. On the contrary, water soluble Cr(VI) species are highly toxic and irritant for human tissues due to their high oxidation potential as well as their ability to cross biological membranes [3–5]. Therefore, in addition to the limit of total Cr content in waters, there are specific maximum levels for Cr(VI). For instance, the World Health Organization (WHO) recommends that the level of Cr(VI) in drinking water should be less than 50 μgL -1 [6]. Consequently, the de- termination and speciation of inorganic species of Cr are a subject of considerable interest. There are a large number of analytical techniques that have been suggested for this purpose. In Table 1, a summary of selected examples of analytical procedures published for Cr speciation in water samples is presented. The analytical method proposed by the Environmental Pro- tection Agency of the United States (EPA) is based on the use of ionic chromatography (IC) [7]. Using this method Cr species can be deter- mined at very low levels but the linear concentration range is limited and IC is a relatively expensive analytical tool. Another analytical alter- native is the combination of preconcentration strategies with atomic spectrometry. Cloud-point extraction (CPE) and solid phase extraction (SPE) have been widely applied for Cr speciation in different types of water samples (see Table 1) [9–12]. However, recent research trends include the use of more environmental friendly analytical preconcentration procedures such as liquid phase microextraction (LPME). The major benefit of this rapid and inexpensive method is the reduction of the use of organic solvents during the extraction step since only several microliters of solvent are needed to concentrate analytes from the sample. Several reviews about the basic principles and main applications of LPME procedures are at present available in the scientific literature [13,14]. Since 2006, LPME procedures have Spectrochimica Acta Part B 115 (2016) 46–51 ⁎ Corresponding author. Tel.: +34 972419839; fax: +34 972418150. E-mail address: eva.margui@udg.edu (E. Marguí). http://dx.doi.org/10.1016/j.sab.2015.11.001 0584-8547/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part B journal homepage: www.elsevier.com/locate/sab