Dual-Phase Microextraction Strategy Combining Electromembrane Extraction and Magnetic Solid-Phase Adsorption with High-Performance Liquid Chromatography with Fluorescence Detection (HPLC-FLD) for the Efficient Determination of Rhodamine Dyes in Processed Foods

This study presents an efficient and highly sensitive method for detecting Rhodamine B and 6 G in complex food matrices. A dual microextraction approach combining electromembrane extraction (EME) and magnetic solid-phase extraction (MSPE) was applied, followed by analysis using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Critical parameters—such as donor and acceptor phase pH, applied voltage, membrane solvent, extraction time, sorbent dosage, adsorption duration, and elution conditions—were systematically optimized to ensure reliable and reproducible performance. The method showed excellent linearity (1.0–200 ng/mL; R2 = 0.9987 for Rhodamine B and 0.9983 for Rhodamine 6 G), with detection limits of 0.9 ng/mL and 1.2 ng/mL, respectively. Recoveries ranged from 92.1% to 101.9% with relative standard deviations (RSDs) below 5%. Application to real food samples—including spicy strips, candies, and chili oil-based bean snacks—confirmed the method’s accuracy and strong matrix tolerance. Compared to conventional microextraction-chromatographic techniques, this method offers notable advantages in speed, sensitivity, and broad applicability. It is a powerful tool for rapid screening and regulatory monitoring of illicit synthetic dyes in food.