Development of salt-induced homogeneous liquid-liquid extraction using a deep eutectic solvent performed in a narrow-bore tube for the extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples.

In this study, a sample preparation procedure based on salt-induced homogeneous liquid-liquid extraction performed in a narrow-bore tube was used for the preconcentration and extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples. To perform the procedure, a mixture of working solution containing sodium chloride, acetonitrile, and a synthesized deep eutectic solvent (as an extraction solvent) was transferred into a narrow tube filled with solid sodium chloride up to a specific level. As the solution flowed through the tube, tiny droplets of the extraction solvent were formed at the boundary between the solution and salt layer. The droplets moved upwards in the tube and eventually collected as a distinct layer on the top of the solution. The separated phase was removed and dispersed into ionized water. After centrifugation, tiny droplets of the extraction solvent containing the analytes were sedimented at the bottom of the tube. The concentrated analytes were measured using flame atomic absorption spectrophotometry. The linear ranges and extraction recoveries were obtained in the ranges of 1.5-100 µg kg-1 and 89.6-94.8%, respectively. The detection limits ranged from 0.35 to 0.48 µg kg-1. Low relative standard deviations (C = 10 µg L-1, n = 6) of 3.1, 2.8, and 3.4% for Zn(II), Cu(II), and Cd(II), respectively, were obtained. Finally, the optimized method was successfully used in determination of concentration of the selected heavy metal ions in various honey samples.

In-situ formation of the adsorbent based on octadecylamine for the extraction of Ag+ ions from aqueous solutions and its determination by microinjection flame atomic absorption spectrometry.

In this research, a dispersive solid phase extraction procedure based on changing the solubility of octadecylamine with pH was proposed to determine Ag+ ions in different water samples. For this purpose, first, the pH of sample solution containing the analyte was adjusted to 10.5. Then desired volume of the octadecylamine dissolved in acidic solution was injected into the solution. Because of the low solubility of octadecylamine in alkaline solution, a cloudy state was formed. The produced octadecylamine particles acted as a complexing agent for Ag+ ions and adsorbent for the formed complex. The obtained cloudy solution was centrifuged and the sedimented particles were removed and dissolved in a diluted nitric acid solution. It was injected into a flame atomic absorption spectrometry to determine the extracted amounts of the analyte. The effect of important parameters such as the amount of octadecylamine, volume of nitric acid, and centrifugation and vortexing conditions on the extraction efficiency of the procedure was studied and optimized. In optimal conditions, the developed method showed a linear range of 0.50-200 µg L-1. The limits of detection and quantification were 0.18 and 0.50 µg L-1, respectively. Extraction recovery was 93.6%. The relative standard deviations were less than 4%. The effectiveness of the method was investigated by determination of Ag+ ions in water and wastewater samples.