Combination of dispersive liquid–liquid microextraction and flame atomic absorption spectrometry for preconcentration and determination of copper in water samples

A simple and rapid dispersive liquid–liquid microextraction procedure based on an ionic liquid (IL-DLLME) was developed for the determination of trace amounts of copper (Cu2+) by flame atomic absorption spectrometry (FAAS). In this work, a small amount of an IL 1-hexyl-3-methylimmidazolium bis(trifluormethylsulfonyl)imid ([Hmim][Tf2N]) as an extraction solvent was dissolved in acetone as a disperser solvent and then the binary solution was rapidly injected by a syringe into the water sample containing Cu2+, which were complexed by 4,4′-bis(dimethylamino)thiobenzophenone (TMK). After preconcentration, the settled IL-phase was dissolved in 40 μL of ethanol and aspirated into the flame atomic absorption spectrometer (FAAS) using a home-made microsample introduction system. Injection of 50 μL volumes of analyte into an air–acetylene flame provided very sensitive spike-like and reproducible signals. Some important IL-DLLME parameters, such as amount of the ionic liquid, chelating reagent concentration, pH and salt concentration were inspected by a (24) full factorial design to identify the most important parameters and their interactions. Under optimum conditions, the calibration graph was linear in the range of 2–50 μg L−1 with a limit of detection of 0.45 μg L−1. The relative standard deviation was 3.3% (n = 5).