Split it into ten groups of ten with a mouse per group. One mouse dies. Split that mouse's group into ten groups of one with one mouse for each group. There is

Split it into ten groups of ten with a mouse per group. One mouse dies. Split that mouse's group into ten groups of one with one mouse for each group. There is a leftover group since one of your mice died, but it doesn't matter. If none of the other mice die you can deduce that the untested bottle contains the poison. Two poison applications to find the right answer, so it only takes ten minutes. Lock the door and tell the guests who arrive you will be there in a minute so you have a bit of breathing room in which to prepare your bottles.