Noninvasive Analysis of Skin Emanations during Cupping Therapy by Thin-Film Solid-Phase Microextraction and...

Cupping therapy is a widely used therapeutic procedure in traditional Chinese medicine, yet its mechanism remains unclear. Some of the literature on the mechanism of cupping relates its beneficial effects to chemical detoxification. Currently, however, there is a lack of rapid, in-situ, and noninvasive analytical approaches for verifying this theory. Here, we developed a method to analyze compounds inside the cupping jar during cupping. After sampling and upconcentration with a thin-film solid-phase microextraction (TF-SPME) membrane during cupping, analytes on the membrane were released via thermal desorption (TD) and then entered a dielectric barrier discharge ionization (DBDI) source mass spectrometer for analysis. Pork skin was first used as surrogate, and we were able to detect five volatile organic compounds that had previously been reported in the literature on the skin surface. Under optimized conditions, the limits of detection (LOD) ranged from 0.003 to 0.063 μg/cm², and a good reproducibility (relative standard deviation ≤8.7%) was achieved. In subsequent cupping experiments on human volunteers, we employed statistical analysis methods to analyze changes in the levels of compounds emanating from the human skin surface before and after cupping, correlated these changes with the clearance of chemicals as described by the detoxification theory. Compared to most previous studies, the method in this work is more convenient, more rapid, noninvasive and can be performed directly on the skin surface.