Supramolecular dispersive liquid–liquid microextraction based solidification of floating organic drops for speciation and spectrophotometric determination of chromium in real samples

Abstract

A novel, sensitive and inexpensive supramolecular dispersive liquid–liquid microextraction method based on the solidification of floating organic drops (SM-DLLME-SFO) has been proposed for the speciation and preconcentration of trace quantities of chromium as a precursor to its determination by UV-Vis spectrophotometery for the first time. The chromium ions are micro-extracted with coacervates composed of reverse micelles formed using decanoic acid and dispersed in tetrahydrofuran–water mixtures. THF plays a double role, as a dispersing solvent and also in the self-assembly of decanoic acid. The method involves the partitioning of the metal chelates, produced from the reaction of Cr(VI) with diphenylcarbazide and sodium dodecyl sulfate in an acidic medium and a combination of SM-DLLME with the solidification of floating organic drops. It combines the advantages of dispersive liquid–liquid microextraction with those based on coacervation and reverse micelles and solidification. All the critical parameters affecting the analytical performance were studied. Under the optimum conditions, the enhancement factor was 50. The detection limit and precision (RSD) were 0.23 μg L⁻¹ and 3.8% (n = 6), respectively. The accuracy of the developed method was evaluated by analyzing a certified reference material and applied successfully to the analysis of several water samples.