We are using three Agilent Qtof's (6550) and all shows annoying, significant contaminants and the nuisances are usually started to be detected after a gradient hits 50%MeCN until the end. Their m/z values are ~200.2386 and 270.3172 as shown below. Is there any group who has experienced to resolve such an issue? Where are they coming from?
Thank you and be safe!