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: Due to the risk of this tachycardia inducing myocardial ischemia , we would not recommend the use in elderly patients of any of the ephedrine / propofol / mixtures studied .
### Output Text:
Due to the risk of this tachycardia inducing myocardial ischemia , we would not recommend the use in elderly patients of any of the <span class="chemical">ephedrine</span> / <span class="chemical">propofol</span> / mixtures studied . 