Ultra-Trace Silver Determination in Biological and Water Samples by Electrothermal Atomic Absorption Spectrometry after Electrodeposition on a Graphite Probe Reza Moradkhani, a Ahmad Rouhollahi, a, * Hamid Shirkhanloo b and Jahan B Ghasemi a a Department of Chemistry, Faculty of Science, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran, Iran b Iranian Petroleum Industry Health Research Institute (IPIHRI), Occupational and Environmental Health Research Center (OEHRC), P.O. Box 11367-74114, Tehran, Iran (Received: Dec. 28, 2011; Accepted: Jun. 22, 2012; Published Online: Feb. 11, 2013; DOI: 10.1002/jccs.201100763) A rapid and simple procedure was developed for selective and sensitive determination of ultra-trace silver in biological and environmental samples using the electrodeposition on a graphite probe modified with palladium followed by electrothermal atomic absorption spectrometry. Several experimental parameters for the electrodeposition, such as deposition potential, electrolyte concentration, pH of solution and depo- sition time were optimized. The calibration graph after preconcentration was linear in the range of 10-250 ngL –1 with correlation coefficient of 0.9989 under the optimum conditions for procedure. The limits of de- tection (LOD) and quantification (LOQ) base on (3s) and (10s) were 2.8 ngL –1 and 9.4 ngL –1 respectively. Related standard deviation (RSD) for eight replicate measurements of 100 ngL –1 silver was 4.3%. Samples were digested completely in a closed microwave digestion system using only perchloric acid, and interfer- ence owing to various cations was also investigated. The proposed procedure was successfully applied to determine silver in blood, urine and some environmental samples with satisfactory analytical results. Keywords: Silver; Palladium; Electrodeposition; Preconcentration; Microwave digestion; Electrothermal atomic absorption spectrometry. INTRODUCTION Silver is one of the commercially and industrially im- portant elements. The widespread use of silver compounds in industry, medicine, jewelry, cloud seeding and electrical instruments has resulted in an increasing silver content of environmental and biological samples. Because of its anti- bacterial properties, silver compounds are often used ex- tensively to disinfect water used for drinking and recre- ation. On the other hand, novel investigations on the inter- action of silver with vital nutrients, especially selenium, copper, vitamins E and B12 have been performed to reveal its potential toxicity. 1-6 Hence, a simple, sensitive and pow- erful method is necessary to determine silver at trace and ultra-trace levels. The direct determination of silver in complex matrix by common methods, such as flame atomic absorption spectrometry (FAAS), 7 electrothermal atomic absorption spectrometry (ETAAS), 8 neutron activation analysis (NAA), 9 inductively coupled plasma atomic emis- sion spectrometry (ICP-AES), 10 is usually difficult because of low concentration of silver and matrix interference and an initial sample pretreatment is necessary. Several differ- ent methods, such as liquid-liquid extraction (LLE), 11 cloud point extraction (CPE), 12 and solid phase extraction (SPE), 13,14 have been used for this purpose. Electrodeposi- tion coupled with electrothermal atomic absorption spec- trometry has been demonstrated to be a powerful method to attain sensitive and selective determination of ultra-trace analysis in a complex matrix. 15 This combined technique has ability to discriminate among very labile, moderated la- bile and inert metal species. This advantage is very impor- tant for determining toxicity levels of different species of elements. In this technique, electrolytic preconcentration is done by plating the metals on a pyrolytic graphite plat- form, 16 high melting-point metal wires 17 or a tubular pyro- lytic graphite coated furnace, 18 used as an electrode. In some of these arrangements, flow systems have been de- signed. 19 After electrodeposition, analyte should be dis- solved from the electrode in a small volume of acid and the whole volume of eluent was injected into the graphite tube atomizer. 20 Matousek et al. have introduced the in-situ electrodeposition-ETAAS technique. 21 Another approach utilizes the electrodeposition of analyte from a larger vol- ume of sample onto the graphite electrode in the form of a disc 22 and, recently, a probe. 23 These graphite parts were di- rectly inserted into the graphite tube atomizer. The aim of the present work is to design an electrodeposition system for preconcentration and separation of ultra-trace amount of silver. The graphite probe was modified with electro- J. Chin. Chem. Soc. 2013, 60, 481-487 © 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 481 JOURNAL OF THE CHINESE CHEMICAL SOCIETY * Corresponding author. Tel: +98 21 230 64 222; E-mail: rouhollahi@kntu.ac.ir Article