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: Carbachol concentrations in serum and urine on day 1 and 2 of hospital admission were analysed by HPLC - mass spectrometry .
### Output Text:
<span class="chemical">Carbachol</span> concentrations in serum and urine on day 1 and 2 of hospital admission were analysed by HPLC - mass spectrometry . 