Objective: To establish a rapid method for determination of sulfur dioxide residue in Chinese herbal medicines. Method: By the principle of in dilute hydrochloric acid

the active metal zinc could restore the sulfurous acid or sulfite to produce hydrogen sulfide

while hydrogen sulfide could lead acetate test paper strips black.We had determined sulfur dioxide residue in 18 batches(3 categories

6 varieties) of Chinese herbal medicines

and then used the 'Chinese Pharmacopoeia' method to verify this experimental method. Result: PbS spots of each batch of Chinese herbal medicines was clear

then compared with standard color card

you could determine the range of sulfur dioxide residue. Conclusion: This method was simple with short measurement time and simple device

it could be applied to rapid qualitative or semiquantitative determination of sulfur dioxide residues in Chinese herbal medicines.