Description authentication methods:
In order to prevent abuse or excessive use of sulfur fumigation of Chinese herbal medicines roughing process, the State Pharmacopoeia Commission in the "Chinese Pharmacopoeia" 2015 edition developed a sulfur dioxide limits and testing methods. Predetermined yam and other 10 kinds of traditional Chinese herbal medicine and the use of sulfur fumigation Pieces, sulfur dioxide residues not more than 400mg / kg, residual sulfur dioxide and other medicines Pieces of not more than 150mg / kg. This limit is to prevent abuse of medicines primary processing or overuse sulfur fumigation.

2015 edition of "Chinese Pharmacopoeia" provides for three detecting sulfur dioxide: acid-base titration, gas chromatography, ion chromatography and the like.
This report uses a first Pharmacopoeia method: acid-base titration method of authentication, accurate and reliable results