Chromatography Forum

Now I need to use CLND as a detector to determine impurites in a chemical compound. Initially we have established a HPLC-ELSD method using TEA-OAC as buffer and pH 7.0 is very important for chromatographic separation. So we want to find a buffer that can replace TEA as it is not applicable for CLND. Do you have any suggestions? I appreciate any replys.

Google found this for me...

http://www.expotechusa.com/Catalogs/Ant ... 200701.pdf

Skimmed the article, looks like they used tridecafluoroheptanoic acid (TDFHA) or pentadecafluorooctanoic acid (PDFOA) with CLND.

This article may help as welll...

http://chromatographyonline.findanalyti ... ryId=48336

Thank you for the reply. But it can not be adjusted to pH 7, right?

You're right, sorry about that...

How about a phosphate buffer? Or a carbonate buffer?

This has been the challenge with the CLND detection... finding a volatile base that does not contain nitrogen... Before ANTEK got bought, some money got spent by the company trying to identify or synthesize such bases but without much success... If you need to buffer your mobile phase at pH 7 that would be a problem...

I think I remember people using the second pKa(~6.2) of maleic acid for volatile buffers. Also the carbonate would be a good choice as well.

I think we all agree that finding volatile nitrogen-free acids is not a problem. Finding a volatile nitrogen-free base (which is needed in order to make a buffer at around 7) is the problem...

I am using both ELS and CLND detectors for my work. Most time I am using ammonium acetate. But I always thought these two detectors shared the same mobile phase requirements. I would assume the HPLC-ELSD method using TEA-OAC as buffer and pH 7.0 can be trnasferred to CLND detector without changing anything. It reads in the original post that "TEA as it is not applicable for CLND." Is this information from the product manual or demonstrated experimentally? Thanks for the information.

In my opinion and experience any nitrogen containing additive in the mobile phase will create a huge background. Even additives that can contain some nitrogen impurities can create background. ANTEK used to recommend to dedicate a new HPLC to the detector because once the HPLC have seen ACN or any nitrogen containing additives you will continue to see it for really long time...

Old relevant post: viewtopic.php?t=3559&sid=0bf47d315dad53 ... 176d1e3add

All the detector sees is nitrogen (with the exception of atmospheric nitrogen which is not getting pyrolized at the temperatures used), so I do not see how you would be able to use any nitrogen containing compounds without severely affecting the sensitivity of the instrument.

What is CLND? Are XL and Kostas talking about the same device?

CLND stands for Chemiluminescence Nitrogen Detector for me...

Thanks HW and Petritis for the clarification. I was thinking about something else for CLND.