Unknown peak co eluting with main peak ( pka 2.0)

[Lakshimohan]

hi,

Am facing a problem of co elution of unknown peak along the main peak , which has a high concentration of ion pair reagents in mobile phase & the unknown peak is not coming repeatedly it comes some time & some time not, it's an upload method , any suggestion ?

[tom jupille]

Not without a lot more information.

What is the k' value of your main peak? and what is the k' value of the unknown peak when it occurs?
How wide is the unknown peak compared to the main peak?
Do you see the unknown peak if you inject a mobile phase blank?

[Lakshimohan]

Hi ,

The k' value of main peak is 6.3 and the main peak is 6.1 . The unknown peak is not wide as the main peak. In the blank injection there is no unknown peak.

Thanks

[Vlad Orlovsky]

What is the nature of your analytes? You can try to play with pH, if they are ionizable, in order to explore the difference in ionic properties

[Lakshimohan]

What is the nature of your analytes? You can try to play with pH, if they are ionizable, in order to explore the difference in ionic properties

The analyte is an amino aromatic carboxylic acid, the mobile phase is with two different pH according to the dual pka of the analyte,

[Vlad Orlovsky]

you need to use mixed-mode where ion-pairing is attached to the surface of the silica:
http://www.sielc.com/Compound-4-Aminobenzoic-Acid.html
http://www.sielc.com/Compound-4-Aminosa ... -Acid.html
http://www.sielc.com/Compound-Phenylalanine.html


Here how it works, you employ 2-D approach :
http://www.sielc.com/Technology_2D_Properties.html

Contact me if you have questions.