Fabrication of Oxidized Acupuncture Needles

The fabrication of oxidized acupuncture needles was simple and straightforward. The tip of an acupuncture needle was first dipped in a mixture of nitric acid (95%) and hydrogen peroxide (30%) (75/25, v/v) solution for 20 min. Oxidation took place as evidenced by bubbles generated on the metal needle surface. The modified tip of the needle was then coated with paraffin wax and placed in a flame of 400–500 °C until it had burned red for 30 s. Cooled to room temperature, the needle was washed by water, alcohol and water, successively. The needle was finally dried under nitrogen and stored for subsequent SMPE and MS analysis. Scanning electron microscope (SEM) analysis was performed on an SU-8000 instrument (Hitachi, Tokyo, Japan) prior to and after such a surface modification.