Is there anyone who has a Waters Acquity UPLC with Tandem Mass Spectrometry in his/her lab? Have you ever struggled with decreased sensitivity for your usual analytes? I want to know your experience about getting the sensitivity back to normal, how did you fix it?
It is the same instrument, the same column type, the same mobile phase combination, the same parameters used, every thing is the same. However, one day the instrument started to loss sensitivity toward my analytes, giving such a decrease response that if I compare the response to those from the day before that crazy day, they look like they are unrelated at all!
I tried a different column (similar part number), newly made mobile phase, replaced the sample cone, and replaced the inline filter. Yet, no improvement to mention.
I wonder if someone has a similar experience in the past and was able to solve it, to share with me what was the problem.
like a routine you should clean your instrument. if it doesn't work, call to the company for maintenance. I had some problems in the past because the instrument was used a lot with different compounds!
Well thank you all for the replies. Cleaning the MS is our first step. We have the sample cone, capillary, ion source and ion guide all cleaned.
We use a simple step to check the cleanliness of our MS system but not always work. Monitor a positive background ions for a minutes then switch to negatiive mode for a while and then switch back to positive mode , if the response rise significantly, an indication of dirty lens and ions guide. Negative mode will dicharge and neutralise some positve ion dirty matrix on surfaces of lens.
Another odd sensitivity issue we encountered was the contaiminated aquoeus buffer with copper ions. Copper ions form adduct with acetonnitrile and suppress normal signal. Back oxide also observed on surface of cone and heated capillary.
You may also want to look at your mobile phase (which you don't describe). Some mobile phases can create a lovely havoc with the uplc tubing, which may take days to clean. An additive may well suppress the MS signal as well.
you can give us more details about the MS parameters and then we can answer your question better. You can use reserpine to check the sensitivity and resolution of your instrument. Or you can try another compound to test your MS. Use infusion mode to see if the intensity is proper
Be careful of the Waters "critically clean" solvent inlet filters. After 4 years of struggling with sensitivity problems on our UPLC-Xevo-TQD system as well as numerous precipitations of unknown white powders at various positions in the system I eventually found that those filters are contaminated brand new from the box. Never got a reply from Waters on my findings and all the money and effort put in. Now things are looking better since I switched to Agilent glass filters but to tell the truth I wouldn't be surprised if other parts of the system is not very chemically inert either. There is no real way of knowing since Waters cannot supply me with data on expected background noise. At least things are looking better and I am looking forward to working again. Don't know if your problem is related to this but perhaps this info might help someone else not to struggle so much.
By the way after 4 years we had checked all our mobile phases and additives, etc. The problem was not there...
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