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: Blood collection and echocardiography were performed at baseline , 1 day after the third cycle , and 1 day after completion of chemotherapy .
### Output Text:
Blood collection and echocardiography were performed at baseline , 1 day after the third cycle , and 1 day after completion of chemotherapy . 