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: The primary end point was the peak increase from base line in the creatinine concentration during the three days after angiography .
### Output Text:
The primary end point was the peak increase from base line in the <span class="chemical">creatinine</span> concentration during the three days after angiography . 