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: Following a 12 - hour exposure of L1210 cells to 50 microM [ 3H ] CB 3717 , 30 % of the extractable radioactivity could be accounted for as CB 3717 tetra - and pentaglutamate , as determined by high - pressure liquid chromatography ( HPLC ) analyses .
### Output Text:
Following a 12 - hour exposure of L1210 cells to 50 microM [ 3H ] <span class="chemical">CB 3717</span> , 30 % of the extractable radioactivity could be accounted for as <span class="chemical">CB 3717</span> tetra - and pentaglutamate , as determined by high - pressure liquid chromatography ( HPLC ) analyses . 