Chromatography Forum

Dear All
Thank you for your valuable suggestion and all.
I got some what new findings. If i will process 5 different lots of plasma and inject the interference will start from second injection onwards. There is no any inference in first injection chromatogram. I was suspecting it may be problem with injector so i changed washing from 70%methanol to 80%acetonitrile but in both times i am getting same pattern.
What will be your personal experience for this?
Is it late eluting peak but i tried for that also i gave run time up to 35 min but there was no late eluting peak also.


Kindly provide you guidance.

Thanking you
PRASHANT

You problem sound very similar to this one...

http://www.sepsci.com/chromforum/viewtopic.php?t=8193

One "quick and dirty" test for a "late eluter" is to compare the width of the interfering peak with the widths of the peaks around it (in the same region of the chromatogram). If the widths are comparable, then the interfering peak probably came from that injection. If the interfering peak is anomalously wide, then it is probably a late eluter.

If it's a late eluter, you might try ramping up the mobile phase strength at the end of the run. Be sure to allow enough time for re-equilibration afterward, and also do the same thing with your standards.

If it's contamination from the same injection, check the thread that Kostas suggested (swapping out the injector needle seals).

Also if you don't need to monitor your late eluter you can try to tap them with guard column and divert them into waste while analyzing the rest of your mixture.

Rapid HPLC Analysis of Complex Mixtures:

http://www.sielc.com/pdf/SIELC_September_2004.pdf