Chromatography Forum

I´m having problems with Desloratadine assay. I cannot reproduce what BP says, retention time 21 minutes. Mobile phase contains SDS and TFA : ACN ratio 57:43. It describes a C18, 4 um, 250 x 4.6 mm column. I tried a lot of columns and nothing, rt like 40 min or more, even with shorter 150 mm columns, and peak shape better not to talk about.... So I start a quick research, and found that column used is a YMC J´spehere ODS-M80. I do not have that column. Carbon load is about 14 % and has a great superficial área, about 500. I do not have similar columns in my lab, and YMC is expensive. Did anyone tried a different column and succeeded? I tried different types, like Hypersil ODS and BDS, Gemini, Luna all 5 um and a Nova-Pak 4 um.

Some vendors have a column comparability table on their website. It may not give you an exact match - you'll need to test your method to prove it - but it might get you on the right path.

I'd be remiss if I didn't also ask the following: which is more expensive, the time you've spent on a bunch of other columns or buying the column you know will work?

Yes, I´ve been looking in waters page before my post. They have a selectivity chart, but this time didn´t help me. And try to convince an accountant to give you a thousand dollars! Not always work.

I think the problem is SDS. The variations between the SDS in different manufacturers are be pretty big. The are even differences between batches in the same manufacturer.
This problem comes in dissolution when you have dissolution media with SDS. Could be the same problem here. Try SDS from different manufacturer as see if there is any changes.
Best of luck

It is true what you are saying. I had that problem with Levotiroxine dissolution, exactly the same. Now, I´m trying with a Gemini and kind of solving my problem.

Yes, I´ve been looking in waters page before my post. They have a selectivity chart, but this time didn´t help me. And try to convince an accountant to give you a thousand dollars! Not always work.

Looking at the YMC column, the closest matches that I can find (from the vendors I typically use) are the Waters Spherisorb ODSB and the Phenomenex SphereClone ODS. You'll have to be careful about the particle size since 4um may be uncommon for these column types and could drive the cost up a bit. If you want to stick with the common particle sizes for these columns, I would first consult the BP. I presume it has a similar chapter to USP <621> that discusses what changes you are allowed to make to particle size for isocratic separations. Make sure you're in compliance with this.

I appreciate that you're on a tight budget. Goodness knows that I've worked at places like that before in my career. But if your accountant is only concerned with the bottom line, you should be able to quickly demonstrate that purchasing the proper column which will work for the monograph will be cheaper in the long run than you buying and trying other columns that might work.