Chromatography Forum

I am doing degradation of a formulated product in NaOH and my analyste is Paracetamol. I can not get any idea about the excipients in this formulation. My purity factor fails at higher concentartionn but pass when I dilute the sample. Is there any reason behind this? I am just wondering how to justify this result. My assay concentration is 100 ppm. So, I take 10 mg equivalent of the sample and dilute to 100ml with NaOH solution. Then, the purty test fail when I inject this sample. I dilute 1 ml of sample to 10ml with Mobile phase and now the purity pass.

PDA "peak purity" test are notoriously unreliable, especially for compounds with similar chromophores. At the lower concentration, you may not have enough of the degradant to differentiate from noise.