Abstract
Gold is a rare and noble metal with atomic number of 79. Several techniques including both spectrometric and electrochemical methods are widely used to determine gold level in real samples. As a result of low concentration of gold in environmental samples, sample preparations such as extraction, clean-up, and pre-concentration before instrumental analysis are mandatory. Thus, a pre-treatment method (dispersive liquid–liquid microextraction (DLLME)) for gold pre-concentration and inductively coupled plasma optical emission spectrometry (ICP-OES) determination is proposed. An extraction method employing DLLME and ICP-OES has been developed for rapid separation, pre-concentration, and determination of ultra-trace amount of Au (III). The extraction of the analyte was performed in the presence of a quaternary ammonium cation, N-methyl-N,N,N-trioctylammonium chloride, (Aliquat 336) as an extractant based on ion-association extraction system. 1-Octanol and acetonitrile were used as extraction and disperser solvents, respectively. The variables affecting the extraction conditions were optimized. A calibration curve in the range of 0.3–100 ng mL−1, the detection limit of 0.09 ng mL−1, an enrichment factor of 150, and an extraction recovery of 74 % were obtained. The precision (RSD %) of the method was 6 % for five replicates and recoveries of 10 ng mL−1 Au(III). The combined DLLME method with ICP-OES can readily determine Au(III) at trace (μg L−1) level using only 10 mL of sample solution (tap, lake, and mining water) without interference by the matrices. This methodology is simple, fast, and low cost which can be used in routine analytical laboratories.
Highlights
Gold is a rare and noble metal with atomic number of 79
DLLME studies related to ion metals involve the use of complexing reagents, ligandless-dispersive liquid–liquid microextraction (LL– DLLME), and ion-pair forming agents
In order to achieve the optimized experimental conditions for high-enrichment factor and quantitative extraction of gold ions by Aliquat 336 through ionassociation DLLME, the influence of some important parameters including concentration of ion-association agent (Aliquat 336), HCl concentration, salt concentration, and nature and volume of both extraction and disperser solvents were investigated. These surveys were done due to their effects on emission signal of gold extracted to organic phase
Summary
Gold is a rare and noble metal with atomic number of 79. Several techniques including both spectrometric and electrochemical methods are widely used to determine gold level in real samples. The average concentration of gold in earth’s crust is approximately 4 μg kg−1 (ppb) and the values of 0.05 and 0.2 ng mL−1 (ppb) were found in sea water and river water, respectively (Lee 1996; Rancis et al 2005) Several techniques including both spectrometric and electrochemical methods are widely used to determine gold in real samples (Shamsipour and Ramezani 2008; Gomez and McLeod 1993; Ye and Beng khoo 1999; Hu et al 2006; de-Souza Periera et al 2014; Ye et al 2014). LLE has been widely used for separation and pre-concentration of gold ions This technique is based on transfer of desired analytes from the primary aqueous sample to water-immiscible solvent (Pena-Periera et al 2009). The ion-pair-based approach has only been applied for gold following the formation of an ion-pair between AuCl4− complex and different counterions such as Victoria Blue R, dicyclohexylamine, benzyldimethyl tetradecyl ammonium, and between AuCN2− complex and Astra Phloxin (De La Calle et al 2011; Kocuroua et al 2010)
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