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: MATERIALS AND METHODS : Our study included patients who were administered 30 - 60 mL of iodinated contrast agent for percutaneous coronary angiography ( PCAG ) , all with creatinine values between 1 . 1 and 3 . 1 mg / dL .
### Output Text:
MATERIALS AND METHODS : Our study included patients who were administered 30 - 60 mL of iodinated <span class="chemical">contrast</span> agent for percutaneous coronary angiography ( PCAG ) , all with <span class="chemical">creatinine</span> values between 1 . 1 and 3 . 1 mg / dL . 