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 FDA - recommended dose during PCI is 25 microg / kg / min ( 350 microg / kg initial bolus ) , adjusted to achieve activated clotting times ( ACTs ) of 300 - 450 sec .
### Output Text:
The FDA - recommended dose during PCI is 25 microg / kg / min ( 350 microg / kg initial bolus ) , adjusted to achieve activated clotting times ( ACTs ) of 300 - 450 sec . 