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
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 mu g L-1) and excellent linearity (4-500 mu g L-1) with a regression coefficient (r(2) = 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 mu g L-1 by means of matrix-matched calibration curves. The method showed good analytical features such as LODs (1.27, 1.42 mu g L-1), LOQs (4.24, 4.73 mu g 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 mu g 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.