Analysis of Nicardipine and it's impurity

[Provetech]

Hi,
We want to analyse batchs of Nicardipine by LC/MS, the impurity are about ten and less the 0.1% each. The nicardipine peak has a big tailing and last more than 1 min. The mobile phase is ACN-Aq. TFA 0.05% (gradient), an the stationnary phase is Kromasil C18- 150-4.6-5µm. Do you have any advises to reduce the tailing because some other products are supposed to be under the main peak (nicardipine).
Thanks

[Rick Jagielski]

There are a few things you can do to improve peak symmetry:

Decrease the total amount of analyte injected onto the column.
Increase the flow rate/pressure
Increase the temperature of the column
Change the mobile phase such that it will more strongly elute the analyte.

Hope this helps.
Thanks
Rick

[Provetech]

Thanks Rick, but the problem is that i must inject 10µL of the solution 1mg/mL to detect enough the impurity, so the loading on the column is quite big but can't be reduced.

[MG]

Increasing the amount of TFA, up to 0.2%, might reduce the tailing, but might also hurt your MS sensitivity.

You could also try a different brand of endcapped column.

Since you have MS, it might be okay if your impurities elute in the tail of the major component. You will still be able to tell them apart from the major component.

[Uwe Neue]

10 microgram does not overload a column. Your issue is silanols on the Kromasil. My recommendation is to go to a mor modern packing. The technologies have improved several times sine Kromasil was made.

I recommend the Sunfire C18 column for your purpose. I also want to tell you that I represent the manufacturer, Waters. Of course, you may not believe me, but indeed technology is progressing....

[james little]

I have had a lot of luck with Varian Metachem Monochrom C18 columns (3 u, 50 x 2). They have excellent peak shape for amines. See their website at:

http://www.metachem.com/order.html

I usually use their 20 x 2 Metaguard precolumn which screws directly onto their analytical column.

For a lot of separations, I run at 40C with a flow of 0.4 ml/min. Solvent A is 10 mmolar ammonium acetate, pH between 3.5 to 4.5 (pH makes a big difference in the separation of component, usually use pH 3.5 to start). Solvent B is 50/50 methanol/acetonitrile. Add 30 ml of solvent B to solvent A to slow microbial growth.

Start at 20-30% Solvent B, take to 85% B in 3-10 minutes depending on complexity of sample. Can go to 100%B if need to "clean" column, return to 70% with no reverse gradient hold 1.5 minutes or so..

Good luck.

[Provetech]

Thanks everyone,
the problem seems to be solved, i tryed an Agilent Eclipse XDB C18 and phosphate buffer and the results are good but i can't use MS with the phosphate, i must use two methods, one to get a good analysis, the other to get th MS signal...