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 recently identified Delta22 - isomer of beta - muricholate contributed for 5 . 4 % and 18 . 3 % ( P < 0 . 01 ) to the pool in control and EE - treated rats , respectively , but could not be detected in bile after exhaustion of the pool .
### Output Text:
The recently identified Delta22 - isomer of beta - muricholate contributed for 5 . 4 % and 18 . 3 % ( P < 0 . 01 ) to the pool in control and <span class="chemical">EE</span> - treated rats , respectively , but could not be detected in bile after exhaustion of the pool . 