Green and simple microextraction method based on deep eutectic solvent-assisted smartphone digital imaging colorimetry (SDIC) for Rhodamine B analysis in food products.

This study employed a deep eutectic solvent-based liquid-liquid microextraction method and smartphone digital image colorimetry to detect and quantify Rhodamine B in foods. The deep eutectic solvent, a green solvent, was prepared by mixing tetrabutylammonium bromide and octanol in a 1:2 ratio. It was observed that Rhodamine B dyestuff readily transitioned to the DES phase, eliminating the need for additional reagents. The impact of various parameters, including DES type, molar ratio, volume, solution pH, ultrasonic time, centrifugation time, and sample volume, on extraction efficiency was examined, and the most effective conditions were determined. Additionally, the diameter of the prepared colorimetric box and the distance between the detector and the sample were investigated, leading to the identification of optimal conditions. The developed method's limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.0054 μg/mL and 0.018 μg/mL, respectively, for the measurements taken using seven parallel blank solutions at 554 nm. The relative standard deviations intraday and interday were 1.29% and 2.03%, respectively. The calibration graph demonstrated good linearity, with a coefficient of determination of 0.9996. The developed method's intraday and interday relative standard deviation values were 2.03% and 1.29%, respectively. Rhodamine B was detected in food samples using the developed method, obtaining extraction recoveries ranging from 95.16 to 103.88%.