isolate vs separate off

isolate

verb
  • To self-isolate. 

  • To separate a pure strain of bacteria etc. from a mixed culture. 

  • To separate a substance in pure form from a mixture. 

  • To insulate, or make free of external influence. 

  • To insulate an electrical component from a source of electricity. 

  • To set apart or cut off from others. 

  • To place in quarantine or isolation. 

noun
  • Something that has been isolated. 

separate off

How often have the words isolate and separate off occurred in a corpus of books? (source: Google Ngram Viewer )