Eco-friendly environmental trace analysis of thorium using a new supramolecular solvent-based liquid-liquid microextraction combined with spectrophotometry

A novel green supramolecular solvent-based liquid-liquid microextraction (SsLLME) method was developed and validated for preconcentration of thorium(IV) in various environmental samples. The presented preconcentration method was based on using 1-decanol/THF as supramolecular solvent phase and quinalizarin as a chelating agent. Thorium(IV)-quinalizarin hydrophobic complex was obtained at pH 6.0, extracted into the supramolecular solvent phase, centrifuged and then the absorbance was measured spectrophotometrically at 590 nm. The impact of some variables on the efficiency of microextraction; pH, amount of quinalizarin, and supramolecular solvent type, ratio and volume, ultrasonication and centrifugation time, sample volume and influence of matrix ions; was optimized. Linearity ranged from 2.0 to 100 μg L−1 with a limit of detection (LOD) of 0.40 μg L−1. The preconcentration factor (PF) was found to be 40. The precision of the method was confirmed with its low RSD% (1.4). The developed method was applied to the analysis of real water and soil samples. The validity was checked with certified reference materials such as IAEA Lake Sediment SL-1 and IAEA-soil-7.