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: The pH adjustment of standard lidocaine can be accomplished easily in the catheterization laboratory before injection and results in a reduction of the pain occurring during the infiltration of tissues .
### Output Text:
The pH adjustment of standard <span class="chemical">lidocaine</span> can be accomplished easily in the catheterization laboratory before injection and results in a reduction of the pain occurring during the infiltration of tissues . 