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: GNC92H2 was delivered 30 min before , concomitantly or 3 min after cocaine treatment .
### Output Text:
<span class="chemical">GNC92H2</span> was delivered 30 min before , concomitantly or 3 min after <span class="chemical">cocaine</span> treatment . 