Chromatography Forum

Hello,
i was performing dissolution test on 7 tablets then wrote a sequence:
medium
st1 (sst 5x)
st2
st1
sample1
.
.
sample7
st1

sst was less then 2% but one of that sample was too high (170%). I purged injector and HPLC system, after that the result was corresponding. What could be wrong? What could be a reason for too high area?

What could be a reason for too high area?

Since a repeat injection of that sample gave consistent results, you must look "upstream" to find the problem. A couple of possibilities:
that tablet was actually bad?
a dlution error (especially if manual prep)?

Thanks for advice but tablets are ok. I injected the same vials once again and got expected results about 100%. It was an error on HPLC system. Samples arent diluted.

Iam looking for a reason for too high area. In the past we have some problems with
bubbles in hplc, problems with a needle... but I have never got that high difference in injections before.

Sometimes you get results that are wrong for no reason than anyone can work out. That is why you have a procedure for re-injections and re-analysis in response to an out of specification result. Only repeated wrong results are both a cause for concern and possible to troubleshoot.

Peter

7???

Its true, sometimes get unexpected results for no reason. But i have no idea what kind of mistake could be in hplc system to get so higher area. Air in hplc or air in needle....?