Ballpoint tip-protected oil-in-salt liquid-phase microextraction with high performance liquid chromatography for the determination of magnolol and honokiol from cortex Magnoliae officinalis

摘要

A ballpoint tip-protected oil-in-salt liquid-phase microextraction protocol coupled with high performance liquid chromatography with ultraviolet detection is reported for the preconcentration and determination of trace magnolol and honokiol in cortex Mangnolia officinalis. A stainless steel ballpoint tip filled with n-hexanol in cavity was immersed in sodium chloride solution to form oil-in-salt double membranes in its open tail which was used as the microextraction device. The experimental variables affecting the performance, such as the extraction solvent, sample pH, extraction time, agitation speed, salting-out location, salt concentration, and immersion time in the sodium chloride solution, were optimized in detail. Under the optimized conditions, the enrichment factors for honokiol and magnolol were 73 and 76, and the extraction efficiencies were 23.4% and 24.3%, respectively. The linear ranges were from 0.004 to 4 mu g mL(-1) for honokiol and 0.006 to 6 mu g mL(-1) for magnolol with coefficients of determination (R-2) exceeding 0.9940 for both analytes. Detection limits from 0.4 to 0.6 ng mL(-1) and quantification limits from 0.8 to 1.2 ng mL(-1) were obtained, respectively. Satisfactory precision (4.4% to 9.7%) and accuracy (84.5% to 99.8%) were obtained. In addition, the enrichment factors and extraction efficiencies of the analytes were determined. The proposed procedure, compared with ballpoint tip-protected liquid-phase microextraction or other microextraction protocols, is simple, convenient and efficient for concentrating and enriching trace magnolol and honokiol in complex matrix.