Phenolic compounds determination in stingless bee by dispersive liquid-liquid microextraction coupled with capillary electrophoresis - diode array detection

A dispersive liquid-liquid microextraction (DLLME) coupled to capillary electrophoresis with diode array detection (CE-DAD) for determination of sixteen phenolic compounds (PCs) is described. DLLME conditions that affect extraction performance were investigated using single-factor variable experiments. The PCs were extracted using ethyl acetate as extraction solvent and acetonitrile as dispersive solvent. The separation was achieved using fused-silica capillary with buffer constituted of 40 mmol L-1 borax (pH 9.3) and 10 % (v/v) ethanol. Voltage of 20 kV, cassette temperature of 25 °C, hydrodynamic injection (30 mbar for 6 s) and variable UV detection wavelengths were applied. The PCs were separated in < 32 min. Calibration curves were linear (r2 > 0.998) within 1-20 mg L-1 for naringin and catechin hydrate, and 0.3-20 mg L-1 for other PCs. Detection limits were 0.01-0.52 mg L-1, relative standard deviations of ≤ 2.39 % (migration times) and ≤ 5.66 % (peak areas) were obtained. The method exhibited good recoveries (85.2-110.7 %), with enrichment factors of 1.79-13.94 and greenness score of 0.35 (AGREEprep) and 0.54 (AGREE). The validated method was applied for determination of PCs in Tualang and stingless bee honey. These results demonstrated the potential of DLLME-CE-DAD as a simple, and environmentally friendly method to quantify PCs in SBH.