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: In one patient , enflurane administered during a donor nephrectomy resulted in unexpected partial motor seizures .
### Output Text:
In one patient , <span class="chemical">enflurane</span> administered during a donor nephrectomy resulted in unexpected partial motor seizures . 