Monitoring of some trace metals in honeys by flame atomic absorption spectrometry after ultrasound assisted-dispersive liquid liquid microextraction using natural deep eutectic solvent

Abstract

In the present study, a simple, low-cost and green ultrasound assisted- dispersive liquid liquid microextraction (UA-DLLME) procedure was developed for monitoring of trace copper (Cu), cadmium (Cd) and lead (Pb) in honey prior to their analysis by flame atomic absorption spectrometry (FAAS). The method is based on ion-pair formation between anionic citrate chelates of each analyte and triphenylmethane group dicationic dye, Methyl green (MeG2+) at pH 5.5, and then extraction of the formed complexes into micro-drops of extraction solvent. Natural deep eutectic solvent (NADES) as extraction solvent was easily synthesized by mixing citric acid-sucrose at mole ratio of 3:2, and used in extraction process. Some parameters affecting extraction efficiency were studied and optimized in detail. Under the optimum conditions, good linear working ranges (0.9–1050 μg kg−1 for Cu, 1.5–675 μg kg−1 for Cd, and 3–1200 μg kg−1 for Pb) was obtained when considered 0.5 g of sample and 1.5 mL of the pre-treated sample solution after dilution of 5-fold for Cd and 25-fold for Cu and Pb, and the limits of detection and quantification were in the range of 0.23–0.87 and 0.78–2.94 μg kg−1 for the analytes, respectively. From analysis results, it was observed that the accuracy (as recovery %), and intra-day/inter-day precision (as relative standard deviation%) were in the range of 90.3–98.4% and 2.0–5.2%, respectively. The method was statistically validated by analysis of a certified reference material. The method was successfully applied to the analysis of low levels of Cu, Cd and Pb in selected honey samples.