Chromatography Forum

Dear all ,
lately my lab have received a new method for tobramycin determination, this new method don't use derivatization as USP did , its mobile phase is 100% buffer solution of pH 10 , on C18 column , and wavelength , 210 nm , so my questions if you can help me , did anyone experienced a 100% aqueous mobile phase ?!! i have read that it may cause column collapse , secondly what is your opinion in injecting tobramycin as is without derivatization ?
regarding that USP method for determination of tobramycin uses derivatization with 4-floro,2,4-dinitro benzene

Many C18 columns nowadays can handle 100% aqueous mobile phase. pH 10 is a bigger problem, but i'm quite sure columns are available for that.

Which particular column does the method mention?

Hi Rndirk,
it is X-Bridge (waters)

I agree with the previous post. There are columns out there that can def handle 100% aqueous. Not sure about the ph though. Also not sure the xbridge can handle 100% aqueous. It is a pretty tough column but what you want is a t3 c18 column from waters or anything that says aquasil from other manufacturers. I believe phenomenex also has Luna c18 columns but I forget the name of their 100% aqueous line of columns. Just note that the xbridge and other c18 columns will seem fine for a little while if you try 100% aqueous but over time you will experience dewetting and column collapse of the stationary phase. So I would highly recommend looking into the columns that can handle 100% aw for long periods of time

Many methods use 100% aqueous mobile phases and conventional ODS columns (non-"aqua-ODS"):
https://extranet.edqm.eu/4DLink1/4DCGI/ ... w/mono/611
https://extranet.edqm.eu/4DLink1/4DCGI/ ... w/mono/685

In order to prevent the stationary phase dewetting, often it is enough to pre-wash the ODS column with a water/organic eluent, then switch to the 100% aqueous mobile phase without stopping the flow, and then proceed with the analysis without stopping the flow.