title: Lab-on-paper with dual electrochemical/colorimetric detection for simultaneous determination of gold and iron.
abstract: A novel lab-on-paper device combining electrochemical and colorimetric detection for the rapid screening of Au(III) in the presence of a common interference, Fe(III), in industrial waste solutions is presented here. With dilute aqua regia (0.1 M HCl + 0.05 M HNO(3)) as the supporting electrolyte, square wave voltammetry on paper provided a well-defined reduction peak for Au(III) at approximately 287 +/- 12 mV vs Ag/AgCl. Under the optimized working conditions, the calibration curve showed good linearity in the concentration range of 1-200 ppm of Au(III) with a correlation coefficient of 0.997. The limit of detection (LOD) of the proposed method is 1 ppm. Interferences from various cations were also studied. Fe(III) is the only metal that affects the electrochemical determination of Au(III) when present above a 2.5-fold excess concentration of that of the Au(III). To overcome this limitation, a colorimetric method was used to simultaneously detect Fe(III) as a screening tool. The procedure was then successfully applied to determine Au(III) in gold-refining waste solutions. The results are in agreement with those obtained from inductively coupled plasma-atomic emission spectrometry (ICP-AES).
authors.affiliation: Sensor Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
authors.forename: Amara
authors.initials: A
authors.lastname: Apilux
authors.forename: Wijitar
authors.initials: W
authors.lastname: Dungchai
authors.forename: Weena
authors.initials: W
authors.lastname: Siangproh
authors.forename: Narong
authors.initials: N
authors.lastname: Praphairaksit
authors.forename: Charles S
authors.initials: CS
authors.lastname: Henry
authors.forename: Orawon
authors.initials: O
authors.lastname: Chailapakul
mesh_terms: D003124:Colorimetry / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D006046:Gold / Q000032:analysis*; D007501:Iron / Q000032:analysis*; D057230:Limit of Detection
chemical_list: D006046:Gold; D007501:Iron