Ultrasound-Assisted Ionic Liquid Dispersive Liquid–Liquid Microextraction for Trace Copper Determination by GFAAS in Environmental and Biological Matrices

Accurate determination of trace copper (Cu) in complex environmental and biological matrices remains analytically challenging due to matrix interferences and the limited compatibility of many preconcentration approaches with routine instrumentation. In this study, a practical ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (IL-UA-DLLME) procedure was developed as a sample pretreatment strategy for Cu determination by graphite furnace atomic absorption spectrometry (GFAAS). 1-(2-Pyridylazo)-2-naphthol (PAN) was employed as the chelating agent, and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]) served as the extraction solvent. Key experimental parameters affecting extraction performance, including solution pH, concentrations of PAN and [HMIM][PF6], and ultrasonication time, were systematically optimized. Under the optimized conditions, the complete analytical procedure exhibited linearity over the concentration range of 0.5–50 µg L−1 with a correlation coefficient of 0.9997. The detection limit was 0.1 µg L−1, and an extraction recovery of 83.4% was achieved under the optimized conditions. The relative standard deviations were 2.5% (intra-assay) and 4.2% (inter-assay). The applicability of the proposed IL-UA-DLLME–GFAAS workflow was demonstrated through the analysis of environmental water samples and a urine standard reference material, yielding recoveries of 94.8%–106.2% and 96.4%–97.2%, respectively, with satisfactory precision. Overall, the developed approach offers an analytically robust and instrument-compatible pretreatment strategy for routine determination of trace Cu in diverse environmental and biological matrices.