Estrone, also known at oestrone and E1 is a naturally occurring estrogen which is the predominant estrogen in postmenopausal women. It can be found in its long-lived form estrone sulfate. In certain scenarios estrone can be a carcinogen and causes breast pain, nausea, headaches and leg cramps. It was separated on both Obelisc R and Primesep 100 which have unique modes of retention. Method is LC/MS compatible and useful for separating a number of pesticides.