Sensitive Determination of Saponins in Radix et Rhizoma Notoginseng by Charged Aerosol Detector Coupled with HPLC

Abstract With continuous development in analytical instruments over recent years, high performance liquid chromatography (HPLC) with various detectors has become very important tools for routine analysis and quality control of TCMs and botanical medicines. As a new “mass” detector, charged aerosol detector (CAD) provides an alternative detection method, which ultraviolet (UV) is unable to achieve for components owning almost no chromophore in its chemical structures with the lower sensitivity. With the purpose of evaluating the applicability of CAD for the analysis of TCMs, an HPLC-CAD method for simultaneous determination of saponins in Radix et Rhizoma Notoginseng (“Sanqi” in chinese) was established in this contribution, which was successfully applied for quantitation of seven saponins, notoginsenoside R1, ginsenosides Rg1, Re, Rb1, Rg2, Rh1, and Rd, in thirty batches of Sanqi samples. Meanwhile, the LODs and LOQs of UV, ELSD and CAD were compared and the results showed that the CAD method exhibited a lower LOD (0.01 ∼ 0.15 µg) and LOQ (0.04 ∼ 0.41 µg) than UV and ELSD. Furthermore, the CAD exhibited a steadier baseline in gradient elution compared with UV at 203 nm. Also, the HPLC-CAD method presents many apparent advantages of high sensitivity, steady baseline in gradient elution, easy operating, and it was expected to be a sensitive and universal method for analysis of TCMs containing weak UV absorption compounds. It was demonstrated that the content of seven saponins in Radix et Rhizoma Notoginseng did not significantly correlate with the original work nor with the conventional quality standard. Keywords: Charged aerosol detectorevaporative light scattering detectorHPLC Panax notoginseng Radix et Rhizoma Notoginseng saponins ACKNOWLEDGMENTS This work was supported by the program for Distinguished Youth Science Fund of National Natural Science Foundation of China (No. 30525043). We gratefully thank Dr. Xiu-Ming Cui (Wenshan Prefecture Sanqi Research Institute, Yunnan Province, China) for kindly providing the Radix et Rhizoma Notoginseng samples. We are also thankful to Dr. Jian-Bo Wan (Institute of Chinese Medical Sciences, University of Macau, Taipa, Macau, China) for his valuable suggestion for the manuscript preparation. Notes N-: notoginsenoside G-: ginsenoside RSD (%) = (SD/mean) × 100. Recovery (%) = (observed amount − original amount)/spiked amount × 100, and RSD (%) = (SD/mean) × 100. QI: quantity of injecting sample: PA: peak area: Sc: sensitivity of CAD; Se: sensitivity of ELSD. S (sensitivity) = ΔPA/ΔQI. a Quantity (heads): the head numbers of Sanqi per 500 g. b Content: mean value of samples (n = 2). “x”: means those medicinal substances which were purchased from different drugstores or from different markets and the specification of them were not so clear in detail. T.S.: means total content of the seven saponins in Radix et Rhizoma Notoginseng.