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: However , in a similar experiment l - dopa ( 80 - 160 mg / kg ) was without effect .
### Output Text:
However , in a similar experiment <span class="chemical">l - dopa</span> ( 80 - 160 mg / kg ) was without effect . 