Ultrasound-assisted liquid-liquid microextraction based on solidification of floating organic droplet using deep eutectic solvent as disperser for preconcentration of Ni and Co

An ultrasonic-assisted demulsified dispersive liquid-liquid microextraction based on solidification of floating organic droplet (UA-DE-DLLME-SFO) technique was considered for the preconcentration of Co and Ni before their determination by micro sampling flame atomic absorption spectrometry (FAAS). In this method, the sample solution was mixed with 1-dodecanol as an extractant and a deep eutectic solvent (tetrabutylammonium bromide: acetic acid) as a dispersive solvent. The dispersion of extraction solvent was performed through the decomposition of deep eutectic solvent in the sample solution. Ultrasonication promoted the dispersion of the extraction solvent into the sample solution. After dispersing, acetonitrile as a demulsifier was introduced to break down the emulsion quickly without centrifugation. The influence of the experimental variables on the extraction recoveries was optimised. The limits of detection were found to be 0.2 mu g L-1 and 0.4 mu g L-1 with the preconcentration factors of100 for Co and Ni, respectively. The relative standard deviations (RSDs, %) (50 mu g L-1, n = 10) were 2.5% and 3.4%, for Co and Ni, respectively. The accuracy of the method was checked through the analysis of certified reference materials namely NIST SRM 1643bof water sample, SRM 1568aof rice flour, and FAPAS QC material of brown rice (T07370 QC). The recoveries of Co and Ni added in water and food samples were obtained in the range of 92.6-98.5% and 92.9-101.5% respectively.