Large Volume Sample Stacking (LVSS) in Capillary Electrophoresis (CE) with Response Surface Methodology (RSM) for the Determination of Phenolics in Food Samples

Abstract

A capillary electrophoresis method with large volume sample stacking (CE-LVSS) has been developed and validated for the simultaneous determination of seven phenolic compounds: naringin, rutin, carnosic acid, apigenin, quercetin, morin, and chichoric acid. Optimization was carried out by response surface methodology and a set of 20 experiments helped to optimize the parameters such as the concentration of buffer, buffer pH, and applied voltage. Analytes were separated using a 50 µm diameter capillary with 56 cm effective length and an extended light path using 20 mM borate buffer at pH 9.2. The LVSS method was optimized and a three- to fivefold improvement in detectability was achieved with injection at 100 mbar for 20 s followed by polarity switching at –20 kV for 6 s. The linearity values of all seven analytes were observed in the concentration ranges from 0.5 to 50 µg/mL for CE and 0.1 to 25 µg/mL for LVSS. The limits of detection were from 0.012 to 0.241 and 0.003 to 0.086 µg/mL for CE and LVSS. The obtained limits of quantitation were within 0.041 to 0.802 for CE and 0.012 to 0.286 µg/mL for LVSS. The recoveries were between 91.1 and 109.8% and 96.3 and 108.4% for CE and LVSS, respectively. The developed method has been successfully applied for the quantitative determination of analyzed components from food samples that are important sources of these compounds.