Ionic liquid mediated extraction, assisted by ultrasound energy, of available/mobilizable metals from sediment samples

A new extraction method for metals from sediment samples was developed. In this procedure, the chelating agent EDTA was combined with a minimal amount of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim[BF4]), assisted by ultrasound energy. The available analytes -Cd, Cr, Cu, Ni, Pb and Zn- were extracted under optimal conditions for a 12.5 ratio (extractant volume/sample mass) with 0.005 mol L−1 EDTA solution, 0.1 mol L−1 NaHCO3, 5.0 mmol L−1 Bmim[BF4] and 7.0 min of sonication time, using an ultrasonic bath (output power of 160 W). The best extractions were obtained with 100 W (power dissipated in the liquid). These conditions were obtained applying the univariate method. It is important to highlight that the conventional method (extraction with 0.05 mol L−1 EDTA solution only) consumes 6 h to extract available metals from sediment samples selectively, and with the proposed procedure the extraction time is noticeable reduced to 7.0 min. Extractable metal concentrations obtained were measured by flame atomic absorption spectrometry. The results showed good agreement with those obtained by the conventional method using a Student's paired t-test.