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: Pronounced changes in the surface ECG ( cycle length , QT , and QTc ) in relation to the dose of oral d , l - sotalol might identify a subgroup of patients with an increased risk for torsades de pointes .
### Output Text:
Pronounced changes in the surface ECG ( cycle length , QT , and QTc ) in relation to the dose of oral <span class="chemical">d , l - sotalol</span> might identify a subgroup of patients with an increased risk for torsades de pointes . 