Ultrasonic-assisted supramolecular solvent-based liquid phase microextraction of mercury as 1-(2-pyridylazo)-2-naphthol complexes from water samples

A separation-preconcentration method based on supramolecular solvent ultrasonic-assisted liquid-phase microextraction (Ss-USA-LPME) for spectrophotometric determination of mercury as 1-(2-pyridylazo)-2-naphthol (PAN) chelates has been established. Red coloured Hg(II)-PAN hydrophobic complex was extracted into the supramolecular phase (1-decanol/THF) at pH 9.5. The extract was separated from aqueous phase by centrifugation, diluted with ethanol and determined by UV-Vis spectrophotometer at lambda(max) = 560 nm. The influences of important analytical parameters such as pH, amount of PAN, 1-decanol and THF, sample volume and matrix effects for the quantitative recoveries were examined and optimised. Under the optimised experimental conditions, the amount of ligand, 1-decanol and THF were 1.0 x 10(-4) M, 200 mu L and 300 mu L, respectively. The optimum time of ultrasonic bath and centrifugation were found as 2 min and 5 min. A linear calibration graph was obtained linearly in the concentration ranges of 8.31000 mu g L-1. The preconcentration factor was obtained as 20. The limit of detection (LOD) was 2.6 mu g L-1 with the relative standard deviation (RSD) of 2.4% for mercury (C = 100 mu g L-1, n = 7). The validity of the developed Ss-USA-LPME technique was checked with a certified reference material of NIST 1641d. The presented method has been successfully applied to the determination of mercury in water samples.