Chromatography Forum

Hi everyone, we are now working on bioequivalence and bioavailability of drug using system TSQ vantage. So we have some question for someone who have experiences :
1. Everyday it takes about 3-4h to get a stable retention time and reponse for the system suitable test, it's normal or we got a trouble ? (presure of the column get stable fast in about 30min)
2. When we injected the system suitable test, the first inject gave a strange reponse 2-4 times more or less, and all others (5-11 injections) were passed, RSD less than 5% ?

Thanks advance.

This sounds more like an issue with your LC parameteres and equilibration there than an issue with the Vantage..

Thanks Leadazide, we tested reponse on vantage (using syringe with loop on vantage), it seems to be stable, so the thing come from LC. SO we cleaned the sample loop, needle/autosampler, the column overnight. We tested in some differents volume inject (form 5-25) but the reponse was always unstable, especially the first injection (with half of twice reponse with anothers). And the trouble has continued for more than 1 week. So anyone has experience on this trouble ?

kankoc,

what is your LC model?

LC: Dionex Ultimate 3000
A technical of thermo have just done a full test on our systeme, so there are some problems
- RF Ram Q3 test failed, so we have to wait for a new coli box Q3
- Fore pump pressure was to low 1.10 Torr (required 1.4-1.8 Torr) -> we'll change mechanical pump oil to see

The issues you mention here can not affect retention times..

Regarding the fore vacuum try exchanging the ion transfer tube first.. if that starts clogging it will give a low fore vacuum.. a faulty fore pump will give a bad vacuum not a too good vacuum..

Thanks guys, we have changed the main board (AM board) of TSQ (the sample transfer line in ion source blocked was changed ) and the suiable systeme test ok RSD about 2.5% so it seems to be ok.