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: Plasma and liver 15 - F ( 2t ) - IsoP were elevated and reached a plateau after day 2 of VPA treatment compared to control .
### Output Text:
Plasma and liver <span class="chemical">15 - F ( 2t ) - IsoP</span> were elevated and reached a plateau after day 2 of <span class="chemical">VPA</span> treatment compared to control . 