[Determination of phenylethyl alcohol in rose dew by micellar capillary electrochromatography]

Rose dew has emerged as one of the superior products in the field of skin care after rose essential oil. However, at present, there is no quality control standard for rose dew. To this end, a micellar capillary electrochromatography (MEKC) method was developed to determine the amount of phenylethyl alcohol, one of the characteristic components of rose dew. The factors affecting the MEKC performance, including the concentrations of borax and sodium dodecyl sulfate (SDS), separation voltage, injection conditions, and detection conditions, were optimized. The capillary length was selected as 48.5 cm, and the effective capillary length was 40 cm. The new capillary was treated successively with methanol, sodium hydroxide (NaOH) solution, and deionized water for 10 min, 60 min, and 30 min when it was used for the first time. Under the running process, the capillary was flushed with 0.5 mol/L NaOH, deionized water, and running buffer solution (10 mmol/L Na₂B₂O₇+15 mmol/L SDS) for 2 min, 2 min, and 3 min each. Between two runs, the capillary was balanced with the running buffer solution for 5 min. Sample injection was performed under a pressure of 5 kPa for 5 s. The separation voltage was set at a positive value of 20 kV. The capillary was maintained at a constant temperature of 20 ℃ using an air refrigeration system. A photo-diode array (PDA) detector with a detection wavelength range of 190-600 nm was coupled to the capillary for monitoring the target molecule, and the optimum wavelength was fixed at 208 nm. Under the optimized conditions, the rose dew samples could be separated and detected within 7 min. The linearity for phenylethyl alcohol detection was found to be 0.50 to 1000 mg/L, with a correlation coefficient (r²) of 0.9990. The limit of detection (LOD, S/N=3) and limit of quantification (LOQ, S/N=10) of the method were calculated to be 0.091 mg/L and 0.35 mg/L, respectively. The accuracy was tested by spiking phenylethyl alcohol into the rose dew samples at mass concentrations of 10, 100, and 500 g/L. The recoveries ranged from 98.1% to 102.7%, and the relative standard deviations (RSD; n=3) were less than 2.8%. This MEKC method is fast, sensitive, inexpensive, and highly effective for the determination of phenylethyl alcohol in rose dew. With the advantages of good stability, anti-matrix interference ability, and high sensitivity, this method represents a simple, sensitive, accurate, and robust strategy for the quality control of rose dew and related products.