HPLC and Benzaldehyde=> 2 peaks?

[demi_lune]

Hello all,

I observe a double peak well resolved for an injection of benzaldehyde with my HPLC, i use phoshate buffer ph=2.5 with THF 80/20 (isocratic).

Do you think that my second peak could be benzoic acid because benzaldehyde oxidize with O2?

Or is it two forms of benzaldehyde (ionized and neutral form)?

Thank you.

Julien

[zokitano]

Julien,

What kind of detection do you use? If you use UV/VIS PDA detector,
you can record the UV spectra of your peaks. Your first step could be comparing the UV spectra of the peaks and see wether they're similar or different. If they are similar (similar chromophore) you're probably dealing with benzaldehyde and its oxidizing product or chemically similar compound (impurity), but if they're different then one of them probably does not origin from your analyte (benzaldehyde) and is rather contaminant, another compound in your sample or maybe solvent peak.

Hope this helps,
Regards

[shaun78]

This is normal.

Funny this thread is here. I just developed an impurity assay for a product at the company I work at. Amoungst others, there are two potential degradation impurities: Benzaldehyde and Benzoic Acid.

The second, smaller peak you observe in your benzaldehyde injections is benzoic acid, which is caused by the oxidation of benzaldehyde.

Cheers!