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: Urinary sodium , potassium and calcium were elevated in lithium - fed WT but not in lithium - fed PKCa KO mice .
### Output Text:
Urinary <span class="chemical">sodium</span> , <span class="chemical">potassium</span> and <span class="chemical">calcium</span> were elevated in <span class="chemical">lithium</span> - fed WT but not in <span class="chemical">lithium</span> - fed PKCa KO mice . 