Raman mapping as quantitative tool for visual analysis of mineral Chinese medicine

Abstract

To facilitate reliable analysis of inorganic ingredients in mineral Chinese medicine, a validated Raman mapping strategy for assaying aluminum potassium sulfate dodecahydrate (KAl(SO4)2·12H2O) in alumen was reported. In this strategy, the internal standard quantitation and simple pellet method were introduced to minimize the interference from undesirable background. The impact of physical properties (including particle size and compactness) of the as-prepared tablets on Raman signals was also systematically evaluated. Compared with the dramatic signal fluctuation (RSD>25%) observed in random single-point Raman measurement, Raman mapping measurement exhibits significantly higher repeatability (RSD<5%). The entire process can be completed within 30 min. Meanwhile, the spatial visualization distribution of the multiple compounds from the as-prepared tablets was achieved by assigning different colors using Raman mapping with Matlab imaging algorithms. Compared to the titration method commonly used in mineral medicine quantification, the validated Raman mapping strategy for non-destructively analyzing KAl(SO4)2·12H2O greatly simplified the complicated operating steps, and improved the reproducibility of experiment results. This could provide a new window for inorganic sample analysis, particularly in the quantification of mineral medicine.