ABSTRACT
In this work, an automated surfactant-assisted dispersive liquid-liquid microextraction approach based on in-a-syringe concept was developed for the first time. The procedure assumed mixing aqueous sample phase and hydrophilic emulsion containing hexanoic acid and sodium hexanoate in a syringe of flow system. Sodium hexanoate acted as an emulsifier in dispersive liquid-liquid microextraction process and it was required for the formation of supramolecular solvent phase. After spontaneous separation of phases in the syringe, the upper supramolecular solvent phase containing target analytes was withdrawn and analyzed. The procedure was applied to the determination of 13 polycyclic aromatic hydrocarbons in tea infusion by high performance liquid chromatography with fluorescence detection. It was shown that the supramolecular solvent provided effective extraction of polycyclic aromatic hydrocarbons and fast phase separation in the syringe without centrifugation. The enrichment factors were in the range of 38-46. The automated microextraction procedure lasted 4 min including syringe cleaning. Under optimal experimental conditions the linear detection ranges were found to be 0.05-50.00 µg L-1 with limits of detection calculated from a blank test, based on 3σ, 0.02-0.04 µg L-1. Recovery values in the range of 85-105% were achieved for tea infusion with a reproducibility expressed as RSD less than 4.1%.
ABSTRACT
A simple and highly-available air-assisted dispersive liquid-liquid microextraction procedure with organic phase solidiï¬cation (AA-DLLME-OPS) was developed as new approach for pretreatment of complex sample matrix. Menthol was investigated as novel extractant for the AA-DLLME-OPS. In this procedure, a cloudy solution of ï¬ne molten menthol droplets is formed when a mixture of molten menthol and aqueous sample is rapidly aspirated into a dispenser and injected into an extraction vial. In the AA-DLLME-OPS, air bubbles promote molten menthol dispersion into aqueous sample phase. Finally, the obtained mixture is cooled and menthol phase is solidified because of the low melting point, which facilitates collection for analysis. To demonstrate the efficiency of the suggested approach, the AA-DLLME-OPS procedure was applied for the HPLC-UV determination of benzoic and sorbic acids as proof-of-concept analytes in beverages and soy sauce samples. The procedure developed provides microextraction of benzoic and sorbic acids from samples with recovery from 93 to 105% and from 96 to 101%, respectively. Under optimal experimental conditions the linear detection ranges were found to be 0.1-150 mg L-1 for benzoic acid and 0.05-100 mg L-1 for sorbic acid with LODs calculated from a blank test, based on 3σ, 0.03 mg L-1 and 0.02 mg L-1, respectively.
