Botanicals contain a great diversity of compounds that exhibit wide variation in their
physicochemical properties. Although no single analytical method is available to measure
all potentially active components, HPLC with charged aerosol detection is a nearly
universal approach that nonselectively measures any non-volatile and many semi-volatile
compounds; that is, CAD does not require that analytes be ionizable (as required for
mass spectrometry) or contain a chromophore (as required for UV spectrophotometry).
A number of isocratic and gradient HPLC-charged aerosol detection methods were developed
and evaluated for the measurement of phytochemicals extracted from a variety of botanicals
including: flavonolignans from milk thistle (Silybum marianum); triterpene glycosides from black cohosh (Cimicifuga racemosa); ginkgolides and bilobalides from ginkgo (Ginkgo biloba); ginsenosides from ginseng (Panax ginseng); phytoestrogens from soy; ursane and oleanane triterpenes from gotu kola (Centella asiatica); and diterpene glycosides from stevia (Stevia rebaudiana). Analytes showed consistent response independent of chemical structure (typically
<10% variability between compounds corrected for gradient elution). All methods had
a wide dynamic range (˜four orders of magnitude), good sensitivity (typically low
ng levels of detection), and excellent reproducibility (RSDs typically <2%) even at
low detection levels. Comparative data from ELSD and UV detection will also be discussed.
