A public official who is conducting official business with a member of the public should not have an expectation of an inherent right to privacy with regards to the things the official says or does in so far as those things said and done reflect on that public official and their office. To clarify, if you are discussing with the Police Chief something to do with a minor child, the expectation is that the information about the minor child will remain confidential but any speech or action by the Police Chief that is out of line would not carry an expectation under color of law that it is in any way protected as confidential.
The fact that you are vague and unclear about the subject matter you may be recording makes it hard to discuss/advise...but if their is no law that states it is a violation to record then you most likely can without the need to inform...whether you should is an entirely different matter based on the nature of what would be recorded. Whether what you record could be used as evidence against those you record is also another discussion.
Again the above is just opinion.