Hi all, we should develop a HPLC method to separate the components of a formulation which consists of Solvesso, Vinylacetat, a Hydroxy-piperidin-oxyl and a mixture of methacrylate with mineral oil. We can separated these components with a Lichrospher RP 18 (5µm). The Eluent was 30 % acetonitrile, 50 % water and 20 % methanol. The sample was solved in acetonitrile. The problem is, that the mineral oil fall out in the column, because of the water. We didn’t get a separation without water in the eluent. Has anyone an idea, how we can separate the mineral oil from the other components by using RP HPLC?