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: RESULTS : Fourteen of 248 ( 5 . 6 % , 95 % CI 2 . 7 % - 8 . 5 % ) plasma samples were positive by immunoassay testing for benzoylecgonine and no samples ( 0 % , 95 % CI 0 - 1 . 2 % ) were positive for amphetamine .
### Output Text:
RESULTS : Fourteen of 248 ( 5 . 6 % , 95 % CI 2 . 7 % - 8 . 5 % ) plasma samples were positive by immunoassay testing for <span class="chemical">benzoylecgonine</span> and no samples ( 0 % , 95 % CI 0 - 1 . 2 % ) were positive for <span class="chemical">amphetamine</span> . 