Chromatography Forum

What is the typical of %RSD of three triplicate injections from the same sample vial? I am using a Thermo TSQ Quantum LC/MS instrument. I tried to make a standard curve using internal standard. However, the peak area ratio of three replicate (from the same vial, just injected three times successively) was not consistent, the %RSD was 3% to 5%. What is the typical %RSD in similar cases? What are the possible reasons for this? Thanks a lot.

It's quite dependent from your injection and pumping system.
We work with a Waters UPLC and we'd obtain reproducibility around 0.5-1%.

thanks for your reply. Do you think the reproducibility has anything to do with the quality of tuning?

I would say that the HPLC should perform in the <1-2% RSD range of injection reproducibilty. I would calculate this from an n=6 injections though. You should probably take into consideration you're using an LC-MS, so I would not expect to get the exact same reproducibility. This is based on a neat sample too. I don't know if your samples are extracted from something or analyzed neat. If your samples are extracted, I would not be concerned with 3-5% RSD. I can't tell if your issues are from tuning since I don't know enough information on your method.

Do you notice a trend with your sample injections? Does your peak area continue to increase, or decrease? How about retention time? Is the ratio of internal standard area to analyte area proportional?

for HPLC it is 2 or less than 2 % but in case of LCMS/MS it depends on your QA department I mean the STP it can vary from 5 to even 15 %.