If any [ one] of you is at the office is correct.

It needs a bit more context to give you an answer. For example, if I were addressing a group of work colleagues, I might say, "If any of you are at the office this weekend, remember to lock your desks when you leave" alternatively, "If anyone is at the office this weekend, remember to lock your desk when you leave". If you use the singular verb form - "is" , it sounds much better to say "anyone"