I am trying to add a question to ask personal information (email address) as a contact info for future survey. Is there way this kind of personal information is saved separate from the rest of the survey data so while the survey remains anonymous but I get to collect a list of email addresses?
Agreed with @Kate answer.
If you want the second survey ( where you are redirecting to ask other questions except email address ) to be only accessed by people who took first survey then check "HTTP Referer Verification" option in the survey option of second survey.