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: Myoclonic movements are evaluated , which were observed and graded according to clinical severity during the 2 minutes after etomidate injection .
### Output Text:
Myoclonic movements are evaluated , which were observed and graded according to clinical severity during the 2 minutes after <span class="chemical">etomidate</span> injection . 