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 aim of this study was to evaluate changes in the regulation of lipid metabolism , ERK and LDLr expression in the liver of rats exposed to subacute diazinon .
### Output Text:
The aim of this study was to evaluate changes in the regulation of lipid metabolism , ERK and LDLr expression in the liver of rats exposed to subacute <span class="chemical">diazinon</span> . 