ion-pairing agents ???

[rick1112]

Hi
Could anyone provide me the available ion-pairing agents used in RP-HPLC?
And if there are special use for certain ion-pairing agents..please provide me the information regarding it..?
I am planning to try out various ion-pairing agent as a part of method development process..any help regarding the above mentioned query will be useful..

Thanks a lot,

Abhilash

[zokitano]

Dear Abhilash

There are two types of ion-pair reagents: cationic (like tetra-alkyl-ammonium reagents e.g tetrabutylammonium hydroxyde) which are used for separation of anions and acids and anionic (alkyl-sulfonic acids like for e.g pentane sulfonic acid) which are used for separation of cations and bases.

Which type of the ion-pair reagents you'll use depends on the acid-base characteristics of the analyte(s).

Best wishes

[rick1112]

hi
presently we are using TFA for most of our analysis?
would like to any other choices available?

[zokitano]

Please tell us more about your sample(s)/standard(s). Which substance(s) / analyte(s) is(are) considered here.

Regards

[Kostas Petritis]

There are several other anionic ion pairing reagents.

Of the same family as TFA you can find longer perfluoro chain ion pairing reagents (i.e. heptafluorobutyric acid (HFBA) NFPA, TDFHA, PDFOA etc). You can also use alkyl sulfonic acids from hexa to dodecyl...

The longer the ion pairing reagent the longer the equilibration time so keep that in mind...

Here are a couple of publications that use different perfluorocarboxylic acids for the separation of underivatized amino acids and small peptides (but in theory they should work for any ionizable cationic analyte).

Ion-pair reversed-phase liquid chromatography for the determination of polar underivatized amino acids using pefluorinated carboxylic acids as ion pairing agent
K. Petritis, P. Chaimbault, C. Elfakir, M. Dreux
J. Chromatogr. A 833 (1999), 147-155.

Ion-pair reversed phase liquid chromatography electrospray mass spectrometry for the analysis of underivatized small peptides
K. Petritis, S. Brussaux, S. Guenu, C. Elfakir, M. Dreux
J. Chromatogr. A 957 (2002) 173-185