Chromatography Forum

Is it possible for a 100% pure compound to produce a peak purity <100%? What could cause this? Could operating at the pKa of one of the substituent groups cause lower than expected peak purity due to the compound existing is 2 different ionized states? Is PP a useful parameter?

thx

AFAI see ideal peal purity at Agilent 1260 is always ≥ 99.9 % but I can't remember 100 %…

Hi Mike H.,

Mike H. asked:

Is it possible for a 100% pure compound to produce a peak purity <100%? What could cause this? Could operating at the pKa of one of the substituent groups cause lower than expected peak purity due to the compound existing is 2 different ionized states? Is PP a useful parameter?

Yes, it is certainly possible for a "100% pure" compound that, when chromatographed, affords data that indicates that its chromatographic peak is not spectrally homogeneous. I'll add that it is also possible for a "<100%" pure compound that, when chromatographed, affords data that indicates that its chromatographic peak Is spectrally homogeneous.

By spectrally homogeneous, I mean that, within the noise of the HPLC/photodiode array measurement system, that all acquired spectra over the selected range of spectral acquisition for the analyte concentration and at the given separation conditions at that time are indistinguishable from each other.

What could cause the "100% pure" compound to not afford data for a given separation that indicates spectral homogeneity? Mike, you note one cause above, incorrect software settings could also lead to a similar result (particularly with gradient separations and the peak tails vs. the peak apex). Each software package has its own idiosyncrasies, it seems to me.

Is Peak Homogeneity a useful parameter? I'd say yes if it is properly applied, executed and its limitations understood.

Mark Stahl wrote this (Agilent .pdf): 5988-8647EN

Arvind Mittal did a nice YouTube video:

https://www.youtube.com/watch?v=E-Whxm398BE

CHROMacademy wrote this, you'll have to sign up for a Lite membership to view the entire document, sign up is Free.

http://www.chromacademy.com/chromatogra ... ctors.html

Thx. this is extremely helpful.