Vortex assisted-ionic liquid dispersive liquid-liquid microextraction and spectrophotometric determination of quercetin in tea, honey, fruit juice and wine samples after optimization based on response surface methodology.

The aim of our study is to develop a new vortex assisted-ionic liquid dispersive liquid-liquid microextraction (VA-IL-DLLM) method for preconcentration and determination of the quercetin in tea, honey, fruit juice and wine samples by spectrophotometry. The method is based on pH sensitive ion-pair formation between quercetin and rhodamine B at pH 6.5 by donor-acceptor mechanism, and then dispersion of the complex in the fine-drops of ionic liquid (IL). In this context, the effects of pH, concentrations of ion-pairing reagent, the IL, vortex time and dispersive solvent type on the preconcentration process of quercetin were investigated using a 2-level-5-factor central composite half fraction design (CCD) as experimental design for response surface methodology (RSM). Quantitative model was developed to determine the quercetin in food samples, and it is verified by analysis of variance (ANOVA) at a 95% confidence level (P < 0.05). Response surface plots and contour plots obtained by the model are used to determine the interactions of experimental variables. After the optimization, calibration graph was obtained between 35 and 750 µg L-1 with the detection limit of 10.2 µg L-1. The recovery and relative standard deviations (RSD%) were in range of 94-104%, and in range of 2.5-4.2%, respectively. The accuracy and precision of the method were tested by the experimental studies such as recoveries, intermediate precision, trueness and expanded uncertainty. A comparison of the current results to those reported for other studies is also presented.