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: When seen at the emergency department 2 weeks later , she still had severe icterus , pruritus , and hyperbilirubinemia , formed mainly of the conjugated fraction .
### Output Text:
When seen at the emergency department 2 weeks later , she still had severe icterus , pruritus , and hyperbilirubinemia , formed mainly of the conjugated fraction . 