I am writing a research proposal in art history. I had a studio visit to the local artist and had a chance to ask her some questions. Unfortunately, I have not recorded it because, well, I was not even planning to interview her this time. However, in my research proposal, I want to state her personal opinion. Am I even allowed to refer to our personal conversation? Of course, for the research itself, I consider conducting a conventional interview with her once again. But for now, can this be considered as an okay source?
I think it would be dangerous to source an unrecorded interview with a prominent person that involves opinion. Actually, it seems dangerous to do it if it is unrecorded and the rest of the first sentence just adds additional reasons.
If the person, at some point, objects to your characterization of their words you will have some troubles.
However, you can refer to personal communication in general if you have a record of it. One way to obtain the record is to send them a message (mail or email) in which you state your interpretation of their words and ask "(a) did I get it right, and (b) can I use that in a paper I'm writing?"
But a recorded and transcribed interview would also do the trick.
However, don't use things that could possibly be disputed without any agreed upon record, or without permission.
Yes, you are allowed to cite personal conversations. Example.
For a research proposal, if you collected some ideas or concepts from a private discussion, you might see the expert as an educator. Therefore a possibility is to just explain them with your own words without quoting, but crediting the advice you got in the acknowledgement section. Of course make sure of not stealing or diffuse sensitive information or stepping on people feet.
On the contrary in a paper you need stronger citations. I think that a private communication can be an acceptable source only if we are talking of an extremely narrow field and you are quoting detailed explanations from a globally recognized expert on the topic. For instance I have a background in physics of particle accelerators and in my field it is relatively common to cite private communications with project leaders or other main contributors when discussing pretty obscure details which are relevant to the specific study, but are omitted in published reports.