I am assuming that you have made this arrangement fairly recently. Both of my children went to nursery at around the same age, and initially had the same problem (to be fair, my daughter (nearly 2) still cries if I drop her off, but not if daddy does). I know it is really upsetting, but if you need to work and provided you are content that the nursery is excellent and is doing everything you need it to, from my experience you just need to get through it. She's been used to having you 24-7 for a good while now, will be a bit strange for her to get used to initially.
After a couple of weeks, I expect she will still cry when you drop her off, but will stop almost as soon as you've gone - and be perfectly happy right up until home time. She will also get used to the fact that you do return to collect her and so this will lessen her anxiety at the end of the day too. Hope all works out xx