Which column for basic analytes

[fdrca]

Dear all, we are trying to develop an LC-ESI-MS bioanalytical method for a NCE which presents two piperidine rings and a lipophilic biphenyl moiety. With conventional C18 (Ascentis, Supelco) we have tried any possible gradient and modifier without avoiding peak tailing. Can anyone suggest us a column particularly suitable for basic analytes. I was thinking about Waters Symmetry or XTerraMS. Thanks in advance

[Bryan Evans]

For difficult basic drug compounds - we recommend Unison UK-C8
or Unison UK-Phenyl.

Below is an application for Minoxidil (chelating compound) and metabolite using NH4AcOH buffer:
http://www.silvertonesciences.com/files/TI303E.pdf

The C8 and phenyl get the best peak shape. The partially end-capped
column (Cadenza CL-C18) gets the worst peak shape due to silanol activity.

[oscarBAL]

Dear Fdrca.

For analysis of Basic compound I think that Sunfire form Waters is a good option; the reasons are:
These colums have high endcaping so there are low free silanols, remember these silanols can form Hydrogen Bridges with amines and produce tailing.

Also you can use these columns to a very low pH and this is usefull if you want to elute basics.

My other options are Xbridge (better than Xterra) can work too, thanks too the purity of the hybrid particule

Regards.

Oscar

[Uwe Neue]

Without question, the best option for peak shape of basic compounds is a column with an embedded polar group such as XBridge RP18 or SymmetryShield RP18. If you do not want to use a column with an embedded polar group, I would go for the most modern deactivated hybrid packing, XBridge C18.

[danko]

Try lowering pH.
For MS detection you can use formic acid (e.g. 0.1 – 0.2 %)
BTW - why MS detection?

Best regards

[mbicking]

I agree with the last post. Adding simple acids to the mobile phase will protonate the basic functional groups and reduce some (or maybe all) of the tailing problems. You still have enough hydrophobic parts in the molecule, so you should still get some retention.

Also, as others suggested, get a stationary phase with very low silanol activity. To find a partial list of phases, read the "Mac-Mod Comparison Guide to C18 Columns." (www.mac-mod.com). There are several phases listed as "Very Low" activity (Figure 16).

[Stryder08]

Without question, the best option for peak shape of basic compounds is a column with an embedded polar group such as XBridge RP18 or SymmetryShield RP18. If you do not want to use a column with an embedded polar group, I would go for the most modern deactivated hybrid packing, XBridge C18.

In my opinion, the best column ever made is the XTerra RP 18, along with the XTerra MS C18.

[AdrianF]

Uwe may be a little biased as a Waters employee!

I am impressed by the the spec of Gemini-NX from Phenomenex which uses a polymer/silica technology, in some cases it appears to be an improvement on Xbridge.

I have not used the columns - I have just studied their brochure.

[danko]

In my opinion, the best column ever made is the XTerra RP 18, along with the XTerra MS C18.

Stryder08, in which way is the XTerra column the best ever made?

Best Regards

[mbicking]

Just to add in another name:

The ACE C18 also seems to score well for very low silanol activity and peak shape for amitriptylene.

I have never used it, but the data indicate that it is similar to the Xterra series.

[MaryCarson]

Stryder, you're not a Waters employee, too, are you?

[Stryder08]

Stryder, you're not a Waters employee, too, are you?

No. I work at a forensic toxicology laboratory. We are mainly a Waters instrumentation lab as we have four UPLC/TQDs, 2 UPLC/LCT Premier XEs, 1 UPLC/Quattro Premier XE, 1 HPLC/ZQ, 1 HPLC/Quattro Micro, 6 2695 Alliance HPLCs...

We do have a couple of ABI QTraps and a 3200.

I find Waters instruments to be more reliable and easier to use.

[Stryder08]

In my opinion, the best column ever made is the XTerra RP 18, along with the XTerra MS C18.

Stryder08, in which way is the XTerra column the best ever made?

Best Regards

I find/found it to be the most robust column we have ever tried in our lab. Gets the most injections too.

[Uwe Neue]

I think that we are getting a bit off the question posed initially.

There is absolutely no question whatsoever that a column with an embedded polar group gives the best peak shape for basic analytes under any circumstances. You can take the best standard C18 column at low pH, and you will be lucky if you meet the peak shape of an EPG column at any pH, even at pH 7.

There is the issue in LC/MS that you can see the bleed of the EPG ligand, while you do not see a C18. But this is happening at one particular m/c ratio and can be ignored. There is also the issue that not all EPG columns are created equal, but I want to stay out of this at this time to avoid any suspicion of commercialism.

[adam]

Uwe

We also use the polar embedded Xterra columns quite a bit in our lab. Do I understand right that you would advocate your Xbridge and symmetry shield columns as better than the Xterra line - for peak symmetry.

Maybe you could provide one or two sentences on what circumstances you would recommend each of these three columns.

Thanks