How can you identify unknown radioisotopes in a substance?

at work we use 18F. we get it from radioactive water. it is ped through a seppak and the waste is 18O. however when this 18O is yzed with a gamma counter there are several other peaks in front of it. how can i identify these? the gamma counter requires standards and for one to know what is in the solution. is there a device that measures unknown samples?