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: OBJECTIVE : To study tremor side effects of salbutamol an easily applicable , quick and low - priced method is needed .
### Output Text:
OBJECTIVE : To study tremor side effects of <span class="chemical">salbutamol</span> an easily applicable , quick and low - priced method is needed . 