By Anonymous on Wednesday, March 12, 2003 - 03:25 am:
I am developing a method involving quantitating Degradation products and impurities. To be able to detect/quantitate the degradation products/impurities, the concentration of one of the actives is too strong, thus overloading the column and flood the detector. The baseline after that particular peak (concentrated analyte) was fine in the first run of approx. 40 injections. However in the next run, all the baselines after that peak went up and down again for approx 4mins.making integration of the small peaks in that region difficult. This did not happen in the blank and in the samples where that particular active is absent. But this also did not happen when the very same column and very same mobile phases were put on a different system (different brand)ie. the baseine was good.
Has anyone encountered this problem?
By Chempara on Wednesday, March 12, 2003 - 10:13 am:
Is this substance basic or acidic? It's possible that you have detoriated the silica in the column due to extreme high or low pH created by the substance itself
By Anonymous on Wednesday, March 12, 2003 - 01:49 pm:
If the silica were destroyed the column would not perform on the other system....
By Anonymous on Thursday, March 13, 2003 - 03:35 am:
This problem could be due to following reasons,
1. The system u r using has got more Dead volume than the other.check the plumbing and length of tubing.
2.le me know the kind of injection procedure in both the system?? is it loop ? or on-line injection?? they sometimes make difference when injecting conc solutions.
3. Check the difference in detector cell path length?/r they same?
4. R u using gaurd column??if yes the base line drift could be due to gaurd column, change it or use the sme gaurd column in other system as well to see the difference.
Good luck.
By Chris Pohl on Monday, March 17, 2003 - 12:15 pm:
Are you sure your analyte doesn't contain a late eluting impurity? Are you working in an isocratic mode? If so, it might be worth doing a quick gradient scan to see if you have a late eluting impurity with your analyte. In extreme cases, this could also cause your wondering baselines problem. Another way to check this is to simply track the baseline after the last injection to see how long the way the baseline persists (but the patient, it could take hours for everything to clear the column).