Deep eutectic solvent-liquid–liquid microextraction followed by thin-layer chromatography and smartphone digital image colorimetry for the determination of acrylamide in food samples

Background: Acrylamide (AA) is a common food processing contaminant that forms during high-temperature food processing, necessitating sensitive and reliable analytical methods for its determination in complex food matrices. Conventional techniques require costly instrumentation, significant sample preparation, and expert operation. As a result, there is an increasing demand for simple, cost-effective, and environmentally friendly analytical methods that allow for rapid and accurate AA monitoring in food samples. In this study, deep eutectic solvent-based liquid–liquid microextraction (DES-LLME) combined with thin-layer chromatography (TLC) and smartphone digital image colorimetry (SDIC) was developed for the determination of AA in food samples. Results: The final extract, obtained after DES-LLME, was applied onto a TLC plate positioned inside a custom-made colorimetric box and images were captured and split into their red, green, and blue channels; the blue channel intensity exhibiting the highest sensitivity was used for AA quantification after being derivatized with 4-fluoro-2-nitro-5-(piperazin-1-yl) aniline within a reaction time of 5.0 min. Optimum DES-LLME performance was achieved using 300 µL of a choline chloride/phenol (1:4 molar ratio) DES as the extraction solvent, 400 µL of acetonitrile as the demulsification solvent, and a 1.0-min extraction time. Optimum SDIC conditions included an 8.0-cm distance between the TLC plate and the detection camera, illumination at a wavelength of 405 nm with 100.0% brightness from a top-mounted light source. Limits of detection and quantitation were 0.40 and 1.33 µg mg^{− 1}, respectively, with coefficients of determination (R²) exceeding 0.9951 and relative standard deviation below 7.4%. The proposed DES-LLME-TLC-SDIC method was successfully applied to quantify AA in various food matrices, including baby food, biscuits, coffee, dark chocolate, and potato chips, yielding relative recoveries between 87.5% and 106.3%. Conclusions: The proposed DES-LLME-TLC-SDIC method provides a reliable, cost-effective and practical technique for the determination of AA in food samples. Its successful application to diverse food matrices and satisfactory analytical performance highlight its potential for routine food analysis.