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: At 1 - minute intervals during the procedural sedation , until the patient regained baseline mental status at the end of the procedure , a word from a standardized list was read aloud , and the patient was asked to immediately repeat the word to the investigator .
### Output Text:
At 1 - minute intervals during the procedural sedation , until the patient regained baseline mental status at the end of the procedure , a word from a standardized list was read aloud , and the patient was asked to immediately repeat the word to the investigator . 