scopolamine and metamizole

[marciaspuri]

Please,
I´m trying to develop a method to be used in the routine in order to determine scopolamine in association with metamizole. I´ve found a method for metamizole ( HPLC) wich is performed by using Zorbax SB C18 column (5 μm particle size, 4.6 ID x 250 mm) column and a mobile phase composed of Methanol:Water (80:20). The injection volumeis 100 μL. 25 oC was column temperature. DAD wavelength is 254 nm.All samples were prepared in water.
Do you have any suggestions that could help me to develop the method for both substances?

[Gerhard Kratz]

You already have a very good column material. But I would add a buffer to your mobile phase. Scopolamine is a very basic compound and you will get tailing, less with a well adjusted buffer. There should be a monograph minimum in the EP for Scopolamine.