Abstract:

An online pressurized liquid microextraction-turbulent flow chromatography-high performance liquid chromatography (online PLME-TFC-HPLC) platform was configured for simultaneous determination of three phenylethanoid glycosides in Cistanche tubulosa. Micro amount powder of crude material (0.5 mg) was mixed with clean diatomaceous earth and packed into a vessel which then was put into a hollow guard column. To generate high temperature and high pressure, a long polyetheretherketone (PEEK) tube (1000 mm×0.13 mm) was linked to the end of the hollow guard column that was warmed in the column oven (70℃). The water containing 0.1% (v/v) formic acid acted as the extraction solvent and was delivered at 2.5 mL/min. Two electronic 6-port/2-channel valves were responsible for dividing the whole program into extraction and elution phases. The analytes were purified and enriched in a TurboFlow cyclone column, and back-flushed onto a Capcell PAK C₁₈ AQ column under a gradient elution program with 0.1% (v/v) aqueous formic acid-acetonitrile at the elution phase. The ultraviolet wavelength was set at 340 nm to monitor phenylethanoid glycosides. The calibration curves for the three phenylethanoid glycosides revealed good linearities in the range of 1-200 mg/L (r>0.999). The limits of quantification (LOQs) were 0.50 mg/L (echinacoside), 0.25 mg/L (acteoside) and 0.38 mg/L (isoacteoside). The spiked recoveries were in the range of 83.13%-114.00% with the relative standard deviations (RSDs) between 1.89% and 13.34%. All the results indicated that this method is facile, efficient, reliable, and advantageous at time, labor, solvent, and material savings. The method also reduces the degradation risks and is suitable for the determination of phenylethanoid glycosides in Cistanche tubulosa.

Key words: Cistanche tubulosa, high performance liquid chromatography (HPLC), online pressurized liquid microextraction (online PLME), phenylethanoid glycosides, turbulent flow chromatography (TFC)