Constant Carryover

[AA]

Have you changed the injector frit??? Once it gets contaminated it is impossible to un-contaminate.

[seamoro]

Yep i have changed the injector frit....thanks for all ur replies guys so far...........i was thinking if i just ran the gradient without the injector...if no peaks appeared it would suggest the carryover is coming from the injector....right! Just have to figure out now how to turn off the injector with a waters system!...lol

[Bruce Hamilton]

The peaks that are coming off in the Blank are a carbon copy of the chromatography of the sample injection. We know this because we have injected(individual related subsatnces and active peak) them at high concentrations individually. The blank peaks (carryover/ghostpeaks) are at a much smaller level (AU 0.000-0.006) but as i said before nearly a carbon copy as if injected a sample except they are alot smaller.

With the additional information, eg appearance after injection of a blank, new columns, 4 HPLC systems, problem since development, etc., it seems as if your problem may be contamination of the mobile phase. In that case, to confirm, I would suggest performing the test outlined by mbicking above. If it show the mobile phase components/system is the problem, you need to try alternative suppliers of chemicals, and flush all parts of your solvent system.

If that doesn't show the mobile phase and/or solvent system as the source of the problem, you could reconsider some of the questions I posted above, given that the problem apparently may have existed since development.

The other option is to investigate the spectra ( mass or UV ) of the peaks to ascertain if they really are related to the beta lactam APIs.

Bruce Hamilton

[tom jupille]

It's a common problem:

http://www.lcresources.com/resources/TSWiz/hs100.htm

[seamoro]

Thanks guys for all ur help. I finally solved the problem...........just did a days cleaning of the HPLC system with Nitric acid and it got rid of all the carryover. So it was just throughout the hplc system all along

[Jade.Barker]

Just for kicks have you tried water from a different source? I've come across times when there has been peaks from my milli-Q water and not from bottled water and vise versa.

I have seen some variability with our HPLC water too. We are doing ion chromatography in our lab, so I check the pH of the water before making the mobile, and it does vary. I'm guessing it is disolved gasses because we have an inline degasser and the variation doesn't seem to effect the Chromatogram. This might be elementary, but my second guess is tech error, ie: The water jug becoming contaminated with stock solution when making the mobile.