An ultrasound assisted modified solid phase micro-extraction technique for enrichment of cadmium and lead in aqueous extract of coal gangue soil samples

Abstract

The present study was carried out to develop a green and novel ultrasonically modified solid phase micro-extraction method (Um-SPµE) to quantify the cadmium (Cd2+) and lead (Pb2+) in acidic water extract (pH < 6.5) of coal gangue soil (CGS) samples collected from the block II of Thar coal field Sindh Pakistan. The 8-hydroxyquinoline (8-HQ) embedded benzophenone allows quantitative enrichment of the Cd2+ and Pb2+ at pH ∼ 6.0. The ultrasonic energy applied to enhance the dissolution/extraction of hydrophobic complex of Cd2+ and Pb2+ in deep eutectic solvent (DES), which synthesized by mixing of zinc chloride and acetamide at 1:2 mol ratios. The extraction capability of DES was enhanced by addition of a nonionic surfactant (Triton X-114) to improve the phase transfer ratio, to notably enhance the recovery of hydrophobic complex of Cd2+ and lead Pb2+. There were various factors (pH, concentration of ligand, adsorbent quantity, volume of DES and nonionic surfactant, and sonication time), effecting the enrichment factor, preconcentration and % recoveries of both metals; were optimized. The certified reference materials and spiking recovery test were applied to real samples in order to check precision and validity of the developed methodology. The % recoveries of both selected metals were found to be > 98% by applying developed method (p < 0.05).