A new CE method with fluorescence detection is reported on the determination of ofloxacin in milk samples using graphene quantum dots (GQDs) for sensitivity enhancement. Injection of GQDs prior the standards/sample is crucial to increase the antibiotic fluorescence response. Clean‐up and preconcentration steps allowed for a good linear correlation in a concentration range between 50 and 1000 ng/mL for the ofloxacin, detection and quantification limits being 10.7 and 35.5 ng/mL, respectively. Optimal CE conditions for the seven‐fluoroquinolone separation method were assessed in terms of buffer type, pH, and voltage. The selective interaction of GQDs with ofloxacin as model analyte was subsequently studied finding a significant sensitivity improvement; therefore, the analytes would be detected at low concentrations by means of a commercial CE device equipped with a multi‐wavelength photoluminescence detector. Due to the different maximum emission wavelengths of the target compounds and the limitations shown by the single‐wavelength photoluminescence detector coupled to the CE system, we demonstrated the usefulness of the GQD‐assisted sensitivity‐enhanced CE method to determine ofloxacin in milk samples. This work opens an interesting possibility of using GQDs in separation techniques combined with photoluminescence detectors for lowering sensitivity levels typically provided by the mere device.

A capillary electrophoresis method was developed for the determination of coumarin (COUM), ethyl vanillin (EVA), p-hydroxybenzaldehyde (PHB), p-hydroxybenzoic acid (PHBA), vanillin (VAN), vanillic acid (VANA) and vanillic alcohol (VOH) in vanilla products. The measured concentrations are compared to values obtained by liquid chromatography (LC) method. Analytical results, method precision, and accuracy data are presented and limits of detection for the method ranged from 2 to 5 μg/mL. The results obtained are used in monitoring the composition of vanilla flavorings, as well as for confirmation of natural or non-natural origin of vanilla in samples using four selected food samples containing this flavor.