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: Zyban , a sustained - release formulation of bupropion hydrochloride , was recently released in Ireland , as a smoking cessation aid .
### Output Text:
<span class="chemical">Zyban</span> , a sustained - release formulation of <span class="chemical">bupropion hydrochloride</span> , was recently released in Ireland , as a smoking cessation aid . 