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 hydrogen peroxide ( H2O2 ) concentration and ferric reducing antioxidant power ( FRAP ) value were determined .
### Output Text:
Plasma <span class="chemical">hydrogen peroxide</span> ( <span class="chemical">H2O2</span> ) concentration and ferric reducing antioxidant power ( FRAP ) value were determined . 