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: METHODS : S - 53482 was administered dermally to rats at 30 , 100 , and 300 mg / kg during organogenesis , and S - 23121 was administered at 200 , 400 , and 800 mg / kg ( the maximum applicable dose level ) .
### Output Text:
METHODS : <span class="chemical">S - 53482</span> was administered dermally to rats at 30 , 100 , and 300 mg / kg during organogenesis , and <span class="chemical">S - 23121</span> was administered at 200 , 400 , and 800 mg / kg ( the maximum applicable dose level ) . 