Hello,
Since 2019 I determine alkylphenols (4-tetr-octylphenol and 4-nonylphenol) using GC-MS-MS (TQ8050 Shimadzu) and everthing was fine until the last few months. I have no more ideas what could be the reason, so I’m counting on your help.

https://ibb.co/x8kjzPR
First picture shows reference standards I have received so far. One day it started to look like in the second picture.
https://ibb.co/HHM7WNh

I replaced septa, liner, o-ring, ferrules, molecular sieve filter, trap filters, syringe. I cleaned inlet and ion source. I haven’t found any leaks. Conditioning, solvent flushing (hexan), and trimming column (about 1m) doesn’t help. After replacing the column for new one it was ok, but not for long.
I also analyse pesticides (on the same column) and there is everything fine.
I think the metod and reagents doesn’t matter, because we have had the same in other department for years. Only I have that kind of problem.

Kind regards
Kinga Woźnica