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### Input Text: Valproate was withdrawn soon after admission and her cognitive abilities have gradually improved over 3 months of follow - up .
### Output Text:
<span class="chemical">Valproate</span> was withdrawn soon after admission and her cognitive abilities have gradually improved over 3 months of follow - up . 