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compounds in end of injection, shifts and making a large diform peak together

Question asked by carolabo on Feb 23, 2017
Latest reply on Sep 12, 2018 by pwebb


We've been experiencing problems since a little while with our P&T GC/MS for VOC analysis.   We calib with 2 stds, one at conc.2 and the other at conc.20.

The one at conc 20, is as usual.  But the std 2, we lose sensibility for the lasts compounds (1,2,4-trichlorobenzene; naphtalene; 1,2,3-trichlorobenzene).  They are also shifting in retention time and making a large difform peak together in the TIC.

We already done the injector, change the ferrule, cut the column.  Done also the same thing at the interface.  No leaks have been found.

Do someone have ideas to help?