Engineering and Process Optimization of a Novel Ag-Assisted Separation System Using a Naphthalene-Based Functional Ionic Liquid for the Removal of Organic Dyes

A novel Ag-assisted microextraction system based on the naphthalene-functionalized ionic liquid 1-hexyl-3-methylimidazolium 6-hydroxynaphthalene-2-sulfonate ([Hmim][HNS]) was developed for the quantitative determination and selective removal of the food colorant Ponceau 4R from real pharmaceutical and environmental samples, including ibuprofen tablets, acetaminophen tablets, cough syrup, and tap water. The ionic liquid was rationally designed and comprehensively characterized by using FTIR, UV–Vis spectroscopy, and elemental analysis to ensure strong and selective interactions with the target dye. Key process parameters─including ionic liquid dosage, extraction time, pH, temperature, and sample-to-extractant phase ratio─were systematically investigated and optimized through a combination of single-factor screening and Central Composite Design (CCD) to maximize extraction efficiency, analytical sensitivity, and reproducibility. The optimized system demonstrated a high extraction efficiency (92–93%), a remarkable preconcentration factor (∼120), ultrasensitive detection (LOD 0.11 μg/L; LOQ 0.24 μg/L), and excellent recoveries (97.8–99.3%) across pharmaceutical and environmental samples, highlighting the robustness, reproducibility, and potential scalability of the method. This study presents a green and efficient engineering platform for the selective extraction of synthetic dyes, offering a practical tool for quality control, process optimization, and environmental monitoring in industrial and pharmaceutical contexts.