A novel deep eutectic solvent microextraction procedure for enrichment, separation and atomic absorption spectrometric determination of palladium at ultra-trace levels in environmental samples Zeid A. ALOthman a , Mohamed A. Habila a , Erkan Yilmaz b,c,d , Eman A. Alabdullkarem a , Mustafa Soylak d,e,⇑ a Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia b Erciyes University, Faculty of Pharmacy, Dept. of Analytical Chem., 38039 Kayseri, Turkey c Erciyes University Nanotechnology Application and Research Center (ERNAM), 38039 Kayseri, Turkey d Erciyes University, Technology Research & Application Center (TAUM), 38039 Kayseri, Turkey e Erciyes University, Faculty of Sciences, Department of Chemistry, 38039 Kayseri, Turkey article info Article history: Received 20 September 2019 Received in revised form 17 November 2019 Accepted 12 December 2019 Available online 16 December 2019 Keywords: Palladium Marble Catalytic converter Microextraction Deep eutectic solvent FAAS abstract A dispersive deep eutectic solvent microextraction procedure for the separation and preconcentration of palladium from environmental samples has been established prior to its flame atomic absorption spec- trometric determination. The deep eutectic solvent (DES) was prepared by mixing disodium 4,5-dihy droxy-1,3-benzenedisulfonate, hydroxyl ammonium chloride, FeCl 3 and phenol resulting in homogenous solution which used directly for the extraction of palladium. The analytical parameter including pH, amount of deep eutectic solvent and sample volume were optimized. The developed microextraction pro- cedure was found to have tolerance for the common matrix ions in real samples. The optimization studies resulted in pH was suitable at 6.0 with sample volume up to 35 mL. The preconcentration factor was 116. The detection limit was found as 1.18 mgL 1 . The presented microextraction method was applied to determination of palladium in marble mine and catalytic converter samples. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Palladium is an element with high industrial value, as it used in jewelry and catalysis. In addition, palladium is used in producing some medical devices as well as in electrical industries. Further application of palladium is that the catalytic converter inside the cars reduces the exhaust of the vehicle [1–3]. The wide application of palladium in many fields worldwide has led to high spreading rate in the environment, causing more environmental pollution as it classified as toxin [4,5]. The palladium exposure may lead to health hazards such as stomatitis and oral lichen planus. Palladium liquid has burring effect for the skin and eyes. The spreading of the palladium contamination in the environment is still at ultra-traces levels, which is difficult to be accurately monitored by the direct analysis using inductively coupled plasma–mass spectrometer (ICP-MS), flame atomic absorption spectrometer or graphite fur- nace atomic absorption spectrometer (GF-AAS) [6–8] and also the positively or negatively effects of the matrix components of the real samples on the signal of the palladium and other traces by the instrumental techniques [9–12]. Therefore, a preconcentration and separation procedure is required before instrumental determination [6,7]. Jamali et al. [13] investigated a homogeneous liquid-liquid preconcentration steps for effective separation of palladium(II). The extraction process was based on using mixture water /tetrabutylammonium ion (TBA+)/chloroform which enhance pairing of ions. Shamsipur et al. [14] developed a disper- sive liquid-liquid microextraction procedure assed by 2-amino-1- cyclohexene-1-dithiocarboxylic acid for interaction with palla- dium in water/acetone/ chloroform mixture for microextraction and measuring by GF-AAS. Nischkauer et al. [15] applied the silica microparticles to extract palladium from dust samples after their microwave digestion for measuring by ICP-MS. Ghorbani et al. [16] preconcentrated palladium from dust samples by assistance of magnetic nanoparticles as sorbent followed by electrothermal atomic adsorption spectrometry detection. Masllorens et al., [17] used azamacrocyclic ligands for extraction of palladium and mea- sured by ICP-AES. Microextraction techniques for inorganic and organic trace spe- cies by using new generation green solvents including ionic liquids, ferrofluids, supramolecular solvents, switchable solvents and deep https://doi.org/10.1016/j.measurement.2019.107394 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Erciyes University, Faculty of Sciences, Department of Chemistry, 38039 Kayseri, Turkey. E-mail address: soylak@erciyes.edu.tr (M. Soylak). Measurement 153 (2020) 107394 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement