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: Tri - ortho - tolyl phosphate ( TOTP ) , 360 mg / kg , po , and 0 , 0 ' - diisopropyl phosphorofluoridate ( DFP ) , 1 mg / kg sc , were administered to adult White Leghorn chickens 24 hr after they were placed on diets containing 0 to 300 ppm corticosterone .
### Output Text:
<span class="chemical">Tri - ortho - tolyl phosphate</span> ( <span class="chemical">TOTP</span> ) , 360 mg / kg , po , and <span class="chemical">0 , 0 ' - diisopropyl phosphorofluoridate</span> ( <span class="chemical">DFP</span> ) , 1 mg / kg sc , were administered to adult White Leghorn chickens 24 hr after they were placed on diets containing 0 to 300 ppm <span class="chemical">corticosterone</span> . 