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In the present study, the simultaneous preconcentration of copper, cobalt and zinc based on ultrasound-assisted ionic liquid-based dispersive liquid–liquid microextraction as a prior step to their determination by flame atomic absorption spectrometry was developed. Some effective parameters such as type and volume of extraction and dispersive solvents, concentration of complexing agent, pH of sample solution, salting out effect, and sonication time were studied and optimized. Under the optimal conditions (including extraction solvent: 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], 90 mg; dispersive solvent: acetone, 220 μL; complexing agent: N,N′-bis(2-salicylaldiminato)-1,8-diamino-3,6-dioxaoctane, 4.0 × 10^− 2 mol L^− 1; pH of sample: 6.5; without salt addition; and sonication time: 2 min), limits of detection (LODs), linear ranges (LRs), preconcentration factor (PF), enhancement factor (EF …