Objective: To find the steps where problems may occur easily by the method and point out the notes when determining sulfur dioxide in traditional Chinese medicine

thus the operations can be improved and the results can be more accurate. Understanding SO2 pollution of medicinal Codonopsis Radix and Codonopsis Radix samples. Method: The methods for determining sulfur dioxide according to Chinese Pharmacopoeia and European Pharmacopoeia were used to determine sulfur dioxide in Chrysanthemi Flos and Codonopsis Radix. The results and operations were compared

and then the causes of error were analysed. Result: According to the results of Chinese Pharmacopoeia method

6 of 20 samples of Codonopsis Radix over 400 mg · kg-1

10 Chrysanthemi Flos samples were under 30 mg · kg-1

it is up to the grade of 150 mg · kg-1. Conclusion: The experimental results show that the starting point of titration

sulfur dioxide absorption process

the titration end point judgment will affect the results

should be strictly controlled. Chrysanthemi Flos of sulfur dioxide pollution less

Codonopsis Radix pollution is relatively serious

we should strengthen supervision and management the market to provide qualified drugs to ensure drug safety.