Measurement uncertainty for total ash and acid-insoluble ash determination of Chinese materia medica

The total ash and acid-insoluble ash contents of Chinese materia medica (CMM) have been widely used as one of the indices to illustrate the quality as well as purity of herbal medicines. Such an approach has also been adopted by many official organizations in writing monographs for pharmacopoeia worldwide. In the present study, a full validation on the methodology was conducted with the inclusion of various commonly encountered matrices in herbs, namely, leaf, flower, fruit, stem and root. The practice ensures method suitability for a wider scope of matrix variation in CMM. Moreover, in order to comply with the technical requirement of International Organization of Standardization 17025 quality assurance system, the concept of measurement uncertainty has also been incorporated in the present study. Measurement uncertainties for total ash and acid-insoluble ash contents have been estimated.