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: There was a prolonged elimination of the radioactivity after the injection of 14C - 41 099 to rats and dogs .
### Output Text:
There was a prolonged elimination of the radioactivity after the injection of <span class="chemical">14C - 41 099</span> to rats and dogs . 