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: Data were collected on adult cancer patients receiving single - agent cisplatin as an outpatient from January 2011 to September 2012 .
### Output Text:
Data were collected on adult cancer patients receiving single - agent <span class="chemical">cisplatin</span> as an outpatient from January 2011 to September 2012 . 