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: During oral loading with d , l - sotalol , continuous electrocardiographic ( ECG ) monitoring was performed .
### Output Text:
During oral loading with <span class="chemical">d , l - sotalol</span> , continuous electrocardiographic ( ECG ) monitoring was performed . 