Gold Determination by Electrothermal Atomic Absorption Spectrometry After Preconcentration Using Natural Deep Eutectic Solvent Based on Menthol and Camphor

A novel analytical procedure for the determination of gold by electrothermal atomic absorption spectrometry combined with selective liquid–liquid extraction by natural deep eutectic solvents (NADESs) is presented. The extraction ability of the NADESs prepared using menthol, thymol and camphor toward gold in hydrochloric acid solutions was studied. The extraction efficiency was improved by optimizing the parameters including the composition of the NADESs, the volume ratio of organic and aqueous phases, kinetics, and acidity of the solution. Quantitative determination of gold was carried out by electrothermal atomic absorption spectrometry directly in the NADESs phase dissolved in isopropyl alcohol. The extraction recovery of gold from 1 mol/L HCl with the NADESs based on menthol and camphor mixed in a molar ratio 1:1 was 99.7% at an enrichment factor of 100. The limits of detection and quantification of the proposed procedure were 1 μg/L and 3.3 μg/L, respectively, with a relative standard deviation of less than 5%. The developed procedure was applied for determination of gold in the certified reference material of ore, environmental and waste waters.