Single granular activated carbon microextraction and graphite furnace atomic absorption spectrometry determination for trace amount of gold in aqueous and geological samples Jalal Hassan a , Mojtaba Shamsipur b, ⁎, Mohammad-Hadi Karbasi c a Department of Chemistry, Tarbiat Modarres University, Tehran, Iran b Department of Chemistry, Razi University, Kermanshah, Iran c Iranian Mineral Processing Research Center, Ministry of Industry and Mineral, Karaj, Iran abstract article info Article history: Received 13 March 2011 Received in revised form 19 March 2011 Accepted 4 April 2011 Available online 12 April 2011 Keywords: Gold Granular activated carbon Graphite furnace atomic absorption spectrometry Preconcentration A new and simple method was developed for preconcentration trace amount of gold in aqueous and mineral samples. The method was based on the sorption of gold on granular activated carbon (AC) in acidic medium (hydrochloric acid) and subsequently direct determination by graphite furnace atomic absorption spectrometry (GFAAS). A small particle of adsorbent was delivered to small volume of sample. After extraction, AC removed and analyzed directly by GFAAS. Several factors influencing the extraction efficiency, such as the hydrochloric acid concentration, sample volume and extraction time were studied as well as effect of potential interfering ions. The preconcentration factor 50 was obtained. The limit of detection (LOD) of gold in water and soil samples was 0.007 μgL -1 and 0.9 ng g -1 , respectively. The proposed method was applied successfully to the determination of trace amount of gold in environmental and geological samples. In order to validate the developed method, two certified reference materials: Platinum Ore (SARM-7B) and Copper Ore Mill Heads (No. 330) were analyzed and the determined values obtained were in good agreement with the certified values and recovery was obtained in the range of 80–118%. The relative standard deviations (RSD) for the spiking levels of 0.5 μgL -1 in the real samples was 4%, (n = 15). © 2011 Elsevier B.V. All rights reserved. 1. Introduction Noble metals have many applications in fields of petroleum/ chemical industry, agriculture, and medicine. Along with the usage of these elements, they inevitably entered the environment by various means (as an example, emitting into the atmosphere with automobile exhaust gases) [1]. Gold is widely distributed in nature and the chemistry of gold remains an active research area. Some gold (I) compounds are biologically active and used as anti-inflammatory drugs in the treatment of rheumatoid arthritis [2]. However, concentrations of gold in environmental and geological materials are usually too low (even below the detection limit of the instrument) to be determined directly by conventional techniques owning to insufficient sensitivity and matrix interference. The concentration of Au in natural water is in the range from 0.01 to 10 ng L -1 and its concentration is about 4 ng g -1 in basic rocks and 1 ng g -1 in soils. Thus, an effective separation and preconcentration procedure is usually necessary prior to determination. The most widely used techniques for the separation and preconcentration of trace noble metals (gold) include fire assay [3], co-precipitation [4], liquid–liquid extraction [5], ion-exchange and sorption [6]. The determination of trace levels of gold has considerable economic importance. A range of analytical instrument can be employed for the analysis of such samples; these include laser ablation, inductively coupled plasma mass spectrometry after NiS fire assay [3,7] and laser exited atomic fluorescence spectrometry [8]. Flame atomic absorption spectrometry (FAAS) has been reported for the determination of gold at sub-ppm levels in geological and environmental samples [9]. Graphite furnace (GFAAS) or electrother- mal atomic absorption spectrometry (ETAAS) has been reported for the analysis of gold; examples include ETAAS after the in situ enrichment with thiol cotton fiber [10], preconcentration with dispersive liquid–liquid microextraction [11], and after electrochem- ical preconcentration on the graphite ridge probe [12]. Although GFAAS has very low detection limits for large number of elements, the direct determination of trace amount of elements in complicated matrices is usually difficult due to interferences and/or insufficient detection power [13] and some of them needed large volume of sample [14]. Thus separation of analytes from the matrix is undoubtedly effective in avoiding matrix interferences. Activated carbon is highly porous adsorbent material, produced by heating organic matter, such as coal, wood and coconut shell, in the absence of Microchemical Journal 99 (2011) 93–96 ⁎ Corresponding author. Tel.: + 98 21 66438324. E-mail address: mshamsipur@yahoo.com (M. Shamsipur). 0026-265X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.microc.2011.04.003 Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc