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: Pharmacokinetic analyses in 21 patients revealed Pirarubicin plasma T 1 / 2 alpha ( + / - SE ) of 2 . 5 + / - 0 . 85 minutes , T beta 1 / 2 of 25 . 6 + / - 6 . 5 minutes , and T 1 / 2 gamma of 23 . 6 + / - 7 . 6 hours .
### Output Text:
Pharmacokinetic analyses in 21 patients revealed <span class="chemical">Pirarubicin</span> plasma T 1 / 2 alpha ( + / - SE ) of 2 . 5 + / - 0 . 85 minutes , T beta 1 / 2 of 25 . 6 + / - 6 . 5 minutes , and T 1 / 2 gamma of 23 . 6 + / - 7 . 6 hours . 