Loss of Signal Intensity in MS after cleaning the ESI Source
I´m working with an UPLC-System coupled to a Quattro Premier XE. Everytime the ESI-source (sample cone, cone gas cone, ion block and it´s compounds) was cleaned I had problems to get better values for peak area and peak height in comparison to pre-cleaned level. This Problem is also observed on the routine MS (Quattro Micro API). Recently I cleaned just the sample cone and the cone gas cone just because it was obviously contaminated. After replacement and about 1 hour re-equilibration I performed an UPLC-run seperating two substances. The same sample was the last run before cleaning the cone. And now I found just half of the area compared to the level before cleaning. But this only apears for one of the two substances. Substance stability can be excluded as the cause. Are there any ideas?For an earlier cleaning procedure I contacted Waters and they told me to tune the MS with the set-up solution (cat. no. 700003105) before and after cleaning. I tuned the solution by direct injection with 100% MeOH at a flow rate of 0,05 ml/min. Than I cleaned the source and also the probe tip. After replacement I tuned the set-up solution and adjusted the probe tip for maximum signal intensity. The values after cleaning were 2 fold increased for the set-up solution. But the next UPLC-run gave peak areas about 50% compared to the values before cleaning. I readjusted the probe tip but that was time consuming. Is there any trick for the adjustment of the probe tip? And how is it possible to get less peak areas even though tuning with another solution gave increased signals?