Purity determination and uncertainty estimation of natural products sourcing chemical reference substances by high-performance liquid chromatography and differential scanning calorimetry

Abstract

Natural products sourcing chemical reference substances (NPSCRSs) are widely used in the analysis industry to determine the content and quality of food and drug products. Chromatographic techniques have been traditionally used to determine the purity of chemical reference substances (CRSs). However, the uncertainty values of NPSCRSs purity are rarely measured due to the chemical complexity of natural products and the diversity of instrument influencing factors. Recently, differential scanning calorimetry (DSC) technique has been proved to be able to detect the purity of CRSs, but its adaptability for NPSCRSs is rarely researched. Herein, a HPLC-DSC combined method was developed for the purity calibration and uncertainty measurement of 20 NPSCRS samples. As a result, the value of “purity ± uncertainty” was suggested to represent the quantitative result for purity measurement of NPSCRSs. Among four influence factors of HPLC analysis, the influence of peak area was first proposed as the source of uncertainty, and the uncertainty caused by the wavelength was simplified to a five wavelength-based method. As for DSC method using for purity determination of NPSCRSs, it could be used as an alternative and complementary method to verify the purity of a NPSCRS that is more than 98% because of its advantage of practicality, speed, reproducibility, no corresponding reference standard requirement, and no sample preparation is required. Note that, DSC method is not appropriate if the compound lacks standard melting peak, decomposes in the defined temperature range, or exhibits other thermal event (s) which interfere with the melting point of the compound.