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: We also demonstrated that OSCS can be identified in heparin products using a simple , inexpensive , commercially available heparin enzyme immunoassay ( EIA ) kit that has a limit of detection of approximately 0 . 1 % , well below the NOEL .
### Output Text:
We also demonstrated that OSCS can be identified in <span class="chemical">heparin</span> products using a simple , inexpensive , commercially available <span class="chemical">heparin</span> enzyme immunoassay ( EIA ) kit that has a limit of detection of approximately 0 . 1 % , well below the NOEL . 