I am Using Sciex Qtrap 4500 for quantification of nitrosamines (NDMA&NDBA). I am facing issue with higher baseline intensity. When developed the method in APCI the basline was at about 5e4. but now even after cleaning the source (i.e. Changed capillary to new, Curtain plate & Corona needle cleaning, given blank injection overnight ), my base line decreased from 1e6 to 4 e5, but settled at 4 e5 from past 24 hours. can you suggest me how decrease my baseline intensity further to below 1e5. My standard peaks are like noise now.