Internal standard mass spectrum fingerprint: A novel strategy for rapid assessing the quality of Shuang-Huang-Lian oral liquid using wooden-tip electrospray ionization mass spectrometry

In this study, an internal standard (IS) wooden-tip electrospray ionization mass spectrometry (ESI-MS) fingerprint method was developed for rapid quality assessment and control of Shuang-Huang-Lian (SHL) oral liquid, a famous herbal preparation registered by Chinese Pharmacopoeia. Sharp wooden tips with tip-end o.d. of 150–200 μm, which are similar to the diameter of commercially available ESI emitter, were used as solid substrates to extract samples and induce electrospray for mass spectrometric analysis. Various active ingredients present in SHL oral liquid, including organic acids, flavonoids, and phenylethanoid glycosides, etc., were simultaneously detected without any sample pretreatment and chromatographic separation. Perfluorooctanesulfonic acid was used as an IS compound to calculate the content fluctuations of active ingredients, and principal component analysis was applied to the obtained fingerprints to achieve systematically and comprehensively quality assessment of investigated samples. The quality stability and consistency were successfully assessed, the sources of different manufacturers were traced, and the qualified, short expired and long expired products were also distinguished unambiguously. Our experimental data demonstrated that IS ambient mass spectrum fingerprint is a simple and efficient approach for rapid quality assessment and control of herbal medicines.