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: Forearm [ 3H ] - L - arginine extraction was calculated after infusion of [ 3H ] - L - arginine into the brachial artery at a rate of 100 nCi / min for 80 minutes .
### Output Text:
Forearm <span class="chemical">[ 3H ] - L - arginine</span> extraction was calculated after infusion of <span class="chemical">[ 3H ] - L - arginine</span> into the brachial artery at a rate of 100 nCi / min for 80 minutes . 