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: It is postulated that her death was caused by hypersensitivity to suxamethonium , associated with her 5 - day immobilization .
### Output Text:
It is postulated that her death was caused by hypersensitivity to <span class="chemical">suxamethonium</span> , associated with her 5 - day immobilization . 