Don't see why not, unless you were a very naughty lad at Uni! If it's been a year since graduation, you'll probably only get a general 'as far as I am aware' reference, but most ex-tutors are reasonably happy to provide one, in my experience. Are you sure that the company you're being interviewed by wouldn't be happy to accept a ref. from one or more of your interning/voluntary jobs? They're none the less valid for having been short-term placements and I would have thought that a prospective employer would be glad to see that you have been 'around' doing useful stuff. If it were me with the interview, I'd go for references from the most recent 'employer', whether I'd been there short-term or unsalaried. They'd remember me and would know what I was like as an employee, salaried or not! Good luck with the interview!