In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: We concluded that this patient had quinidine hepatotoxicity and believe that this is the first case reported with liver biopsy documentation .
### Output Text:
We concluded that this patient had <span class="chemical">quinidine</span> hepatotoxicity and believe that this is the first case reported with liver biopsy documentation . 