At the beginning, my method was good and I was able to analyze Liraglutide effectively (peak area of Liraglutide 500 ng/mL was 2364616). But, these days, I have been facing problem of decrease in peak area of liraglutide (peak area of liraglutide of 500 ng/mL is 127143).
The dissolving solvents was 50% ACN, since it enhanced more ionization of liraglutide than in water.
[Mobile phase: 0.1% formic acid in water, 0.1% formic acid in ACN)
Still after MS tuning, I could increase the peak area to some extend (intensity during MS tuning was only 2.06e6) but peak area was low still low compared to previous (as that of beginning).
However, there is no problem while analyzing any other samples or reference samples of UPLCMSMS, indicating the instrument status is well.
To confirm, the liraglutide samples that we purchased is causing problem or not, we had checked reference liraglutide also, but the peak area was still low.
Some paper that I have referred for method setup were:
1. An ultrasensitive UPLC-MS/MS assay for the quantification of the therapeutic peptide liraglutide in plasma to assess the oral and nasal bioavailability in beagle dogs
2. UPLC-MS/MS Determination of GLP-1 Analogue, Liraglutide A Bioactive Peptide in Human Plasma
3. Pharmacokinetics and brain distribution of the therapeutic peptide liraglutide by a novel LC–MS/MS analysis
It can give multi-charge ions, so it is important to observe MS spectrum first to see which charge give better signal. Also it is important to check that the compound does not cause a pollution of the autosampler and column, as it has long molecule and may get the surface activity at protonation. In this situation UPLC system will be polluted by compound and peak intensity will be low with high background. Changing of pH may solve the problem in last case.
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