Missing peak in GC-FPD

Hi there, I am using GC-FPD with a CP-Sil 5CB column (sulphur-specific) for sulphur-containing VOC detection. Initially, our purchased standard contains methyl mercaptan (CH3SH), dimethyl sulphide, carbon disulphide and dimethyl disulphide. I then further got standards for hydrogen sulphide (H2S) and sulphur dioxide (SO2). However, after a few injections of SO2 into the column, the CH3SH peak disappeared. I wondered if there was leaking in inlet or problem in liner so I checked leakage and replaced a brand new liner. But the CH3SH peak is still missing whereas the others are fine. I wonder was it the oxygens in SO2 contaminating the column or reacting with CH3SH. Could any experts comment on this or provide some suggestions on how I could clean the column? Or change the settings like changing purge flow/ time or hold time to help? 

  • HI tctsead,

    MeSH should not disappear after injections of SO2.

    • Have you tried an injection of MeSH in a high concentration?
    • Which C-Sil 5 CB column did you use?
    • What's your temperature program and injection temperature?

    Oxygen might not be the problem but moisture as H2O and SO2 form an acid that could damage the phase if the temperatures are not right.



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