Verification method description:
In order to prevent the abuse or excessive use of sulfur fumigation during the primary processing of Chinese medicinal materials, the National Pharmacopoeia Committee has formulated the sulfur dioxide limit standard and detection method in the 2015 edition of the Chinese Pharmacopoeia. It stipulates that the sulfur dioxide residue of 10 traditional Chinese medicinal materials and their decoction pieces that are fumigated with sulfur, such as yam, shall not exceed 400 mg/kg, and the sulfur dioxide residue of other Chinese medicinal materials and their decoction pieces shall not exceed 150 mg/kg. This limit is to prevent the abuse or excessive use of sulfur fumigation during the primary processing of Chinese medicinal materials.

The 2015 edition of the "Chinese Pharmacopoeia" stipulates three methods for detecting sulfur dioxide: acid-base titration, gas chromatography, and ion chromatography.
This report uses the first method of the pharmacopoeia: acid-base titration for method verification, and the experimental results are accurate and reliable