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: METHOD : FS containing aprotinin or different concentrations of tAMCA ( 0 . 5 - 47 . 5 mg / ml ) were applied to the pial surface of the cortex of anaesthetized rats .
### Output Text:
METHOD : FS containing aprotinin or different concentrations of <span class="chemical">tAMCA</span> ( 0 . 5 - 47 . 5 mg / ml ) were applied to the pial surface of the cortex of anaesthetized rats . 