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: Results were confirmed by determination of internucleosomal DNA fragmentation using gel electrophoresis for HL60 cell samples and terminal deoxynucleotidyl transferase assay in HBMP cells .
### Output Text:
Results were confirmed by determination of internucleosomal DNA fragmentation using gel electrophoresis for HL60 cell samples and terminal deoxynucleotidyl transferase assay in HBMP cells . 