Investigation of the processing of calcined and vinegar-quenched ochre samples using 2T2D correlation Raman spectroscopy.

The application of mineral medicine has a long history of thousands of years, and the processing of traditional Chinese medicine (TCM) is a unique pharmaceutical technology. However, the processing of most mineral medicines is still unclear and requires in-depth and systematic research. To achieve accurate identification of mineral medicines and elucidate their variation from a chemical perspective, two-trace two-dimensional (2T2D) correlation Raman spectroscopy was used. This is the first time that 2T2D correlation analysis has been used to elucidate the processing for TCM. Since the properties of mineral medicines change with processing (e.g., calcined and vinegar-quenched ochre), X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy were used as auxiliary tools to investigate and validate the Raman spectroscopy findings. Comparative analysis of the Raman spectra of ochre and its processed products revealed that the crystal structure and composition of the calcined ochre and vinegar-quenched ochre changed and that their purity improved. Based on these results, 2T2D correlation Raman spectroscopy method has excellent analytical performance, enables the rapid identification of mineral drugs and a deeper understanding of their processing. Our study also provides new concepts and methods for the quality detection of mineral drugs.