Sequential determination of iron species in food samples by new task specific ionic liquid based in situ dispersive liquid–liquid microextraction prior to flame atomic absorption spectrometry

Abstract

In this work, we report the synthesis of two new task-specific ionic liquids (TSILs) of N-methyl-N-ethyl imidazolium bromide functionalized with 5-amino salicylic acid (5-ASA) and 2,2′-thiodiacetic acid (TH) as the chelating agents and extracting solvents. The in situ dispersive liquid–liquid microextraction based on the developed TSILs was employed for the sequential extractions of Fe(II) and Fe(III) from aqueous solutions prior to determination by flame atomic absorption spectrometry (FAAS). An in situ metathesis reaction using KPF₆ salt as an anion-exchange reagent was performed to form hydrophobic ionic liquid microdroplets. Some important variables that might affect the extraction efficiencies were optimized. Under the optimal conditions, linear concentration ranges of 20–120 μg L⁻¹ and 20–80 μg L⁻¹ with detection limits of 7.6 μg L⁻¹ and 8.1 μg L⁻¹ were obtained for determinations of Fe(II) and Fe(III), respectively. The relative standard deviations (RSD) for five replicate measurements of Fe(II) and Fe(III) at 50 μg L⁻¹ were 2.0% and 2.5%, respectively. No considerable interferences have been observed for the investigated co-existing ions. The method has been successfully applied to the analysis of iron species in different food samples with recoveries ranging from 99.7 to 102.5%.