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: Recently , p - aminophenol ( PAP ) , a known potent nephrotoxicant , was identified as a metabolite of APAP in F344 rats .
### Output Text:
Recently , <span class="chemical">p - aminophenol</span> ( <span class="chemical">PAP</span> ) , a known potent nephrotoxicant , was identified as a metabolite of <span class="chemical">APAP</span> in F344 rats . 