Loosing C35-C40 standards sensitivity over time



I have a question. I loose the sensitivity of C35-C40 standards. I usually inject a standard mix (C21-C40) but over the time I loose the high chain length carbons. Either I see very little peaks or I see nothing. If I inject the low carbon chain standard mix (C8-C20) I have no problem at all, I have the same sensitivity over the time. Could anyone help me what to do?


Thanks a lot



  • Hi Zsolt,

    have you solved the problem in the meantime?
    If not, discrimination of higher boiling compounds usually point towards contamination from polar compounds probably contained in your samples that over time accumulate either in the liner of your GC injector or at the column entrance. Have you tried to exchange the liner and/or trimming the column (cut of 30cm) to solve this issue?



  • Hi Jens,


    Thanks a lot for your answer. I already solved the problem. I cleaned the ion source and it is much much more sensitive. The ion source had black contaminations. I also changed the liner but didn't help. I didn't cut from the column. 

    Anyway thanks again. It is always good to discuss things. Actually, after 1 month again the sensitivity dropped down. Now I clean again the ion source. It is change though. 





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