Ion pair vortex assisted-ionic liquid based dispersive liquid-liquid microextraction for selective separation and preconcentration of 4-methylimidazole from caramel colour drinks and foodstuffs prior to its spectrophotometric determination

Abstract

In the study, a simple, fast, easy to use, cost-effective and green analytical method was developed for the selective extraction and determination of 4-methylimidazole (4-MeI) from caramel colored drinks and foods by using vortex assisted-ionic liquid-based dispersive liquid liquid microextraction (VA-IL-DLLM) followed by spectrophotometry. The method is based on ion-pairing of the formed anionic chelate complex, AgIm(ImH)(H2N-C(CH2OH)2(CH2O)− (in fact, where the charged chelate formation and concentration dependent charge transfer proceeds together in aqueous IL medium), between soft Ag+ ions and 4-MeI with cationic soft IL, trihexyl(tetradecyl)phosphonium chloride, Cyphos IL 101 in presence of chelating and redox sensitive biological tris buffer at pH 7.0, and then extraction of the formed ion-pair into the micro-droplets of the IL by help of vortex. Greener IL, Cyphos IL 101 as both extractant and ion-pairing was effectively used together with the dispersive solvent (ethanol) for separation of analyte from sample matrix in extraction process. The important factors influencing extractable ion-pair formation and extraction efficiency were evaluated and optimized in detail. The method has shown a low limit of detection and quantification, LOD and LOQ (1.15 and 3.82 μg L−1) and excellent linearity (4–500 μg L−1) with a regression coefficient (r2 = 0.9917) via calibration based on aqueous standard solutions of 4-MeI in solvent. Also, a validation study was performed on the spiked two quality control samples (honey and tea) at levels of 25, 100 and 300 μg L−1 by means of matrix-matched calibration curves. The method showed good analytical features such as LODs (1.27, 1.42 μg L−1), LOQs (4.24, 4.73 μg L−1), recovery% (91.5–96.3%), repeatability (3.5–6.2%) and reproducibility (4.1–7.6%) without a significant matrix effect in linear working ranges of 5–350 and 4–400 μg L−1 respectively as a measure of accuracy and precision with a sensitivity enhancement factor of 115-fold. After the validation, the method was successfully applied to the determination of low levels of 4-MeI in caramel colour drinks and foodstuffs. The findings have shown that the method is promising for accurate and reproducible detection of 4-MeI in the selected samples with acceptable analytical results.