Development of salt-induced homogenous liquid-liquid extraction based on ternary deep eutectic solvent coupled with dispersive liquid-liquid microextraction for the determination of heavy metals in honey

In this work, a homogenous liquid–liquid extraction method was combined with dispersive liquid–liquid microextraction and utilized for the extraction of Co, Zn, Ni, Cu, Pb, and Tl from honey samples before their determination by inductively coupled plasma-atomic emission spectrometry. For this purpose, firstly, diluted honey solution was transferred into a glass test tube and mixed with a few milliliters of a mixture of n-butanol and choline chloride: menthol: p-aminophenol deep eutectic solvent. A homogenous solution was obtained. After that an appropriate amount of sodium chloride was added into the solution and sonicated for 6 min. During this step, the homogenous solution was broken and the mixture of n-butanol and the deep eutectic solvent mixture was collected on top of the solution. The supernatant phase was removed and quickly injected into deionized water. After centrifugation, the collected phase at the bottom of the tube was injected into the determination system. Under the optimum situations, low limits of detection (0.24–0.74 ng g–1) and quantification (0.79–2.46 ng g–1), high extraction recoveries (80–92%), and good repeatability (relative standard deviations equal to or less than 3.6% and 3.9% for intra– and inter-day precisions, respectively) were acquired. Finally, the offered method was employed for determination of the studied heavy metals in various honey samples marketed in Tabriz city, Iran.