Field Deployable Method for Gold Detection Using Gold Pre-Concentration on Functionalized Surfaces

Gold in a rock is usually associated with other elements, forms nuggets, or is hosted within the crystal lattice of a mineral (e.g., pyrite) and is often heterogeneously distributed and trapped inside the rock matrix even after crushing. Gold can be liberated from these rock matrices by chemical leaching, but then their concentration becomes too low for detection by a portable method due to the dilution effect of the leaching process. In this paper, we present a proof-of-concept method for gold pre-concentration to enable the detection of gold in rock at low levels using a portable technique. Two coating methods, plasma polymerization (PP) and wet chemistry (WC), were utilized to generate surface coatings, which were then compared for their effectiveness in binding gold ions. Laser-induced breakdown spectroscopy (LIBS) was used as a portable technique for the detection of immobilized gold on these modified surfaces. The detection limit for pure gold ions in solution incubated on PP and WC coatings was determined to be as low as 80 ppb. To demonstrate the real-life capability of the method, it was tested for rock sample leachates bearing 300–500 ppb gold.