I have encountered the problem while standardizing the method on HPLC for rifampicin from human plasma. The recovery of rifampicin from plasma exceeds 100%, which could be because of drug degradation in standard concentration samples. I tried different solvents to prepare standard concentration samples, like methanol, mobile phase, ACN, even at different pHs from 5-8.5.
Mobile phase (MP) used ACN: KH2PO4 (0.6M) (60:40)
PH of MP -5-8.5
How was the standard curve prepared? I have not quantified rif myself, but it sounds like this could be a matrix effect, which can sometimes increase the signal compared to pure standard spiked directly into mobile phase. You might want to extract blank plasma and then spike in the standard after to check if that is true. compare that against the pure standard in mobile phase.
Dear Janice,
Thanks for the response. The same has been done and we could not found any difference, for matrix effect, we are getting two peaks with good resolution
Rifampicin=3.317
Matrix-2.15
I think this could not be a matrix effect
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