Hi all! I am using a Waters-TQS micro (LC/MS/MS) in negative ionization mode (MRM) to analyse a few compounds. When doing QC injections (i.e., repeated injections from same vial of standards at a certain concentration) the area response keeps going up with each subsequent injection. Now, my method is 20 minutes long. I do recall that negative mode can take some time to stabilize, hence this might be the reason why I see increasing area responses. But, question is how long would you wait for it to stabilize? Or.... is there something else at play?
Thanks for reading and potentially contributing!
Best!
T
Dear Vasiljevic,
Could you let me know your column conditions? Is it clean? If no, please wash the column with appropriate washing solutions and again try.
Best wishes
To me it seems like an accumulation problem. As already said make sure the conditions of the column are able to wash out your compounds. Also, make sure there is no contamination in the mobile phases that is behind this accumulation.
You can try changing the needle wash solvent, or check the injector precision and report it.
In negative ionization, Method stabilized minimum 2hrs, and what are the diluent using, if diluent using methanol: water, Diluent stabilized at least 1 hr
Other than this please check the gradient programmed in your method
- Badges
- Science method