by
tlahren » Tue Aug 16, 2011 9:48 pm
Depending on the operating temperatures, water can oxidize both the column and parts of the MS. Oxidation in the MS leads to poor tuning and dramatic loss in sensitivity. If you are running a cooler oven gradient (i.e., <100°C or so) water may not damage a good methyl-silane too much. Even using a good purge-and-trap system, some water makes it through the GC and into the MS. I'm not sure how much per injection it would be on a µL scale but it's actually quite a bit. The MS (Agilent 5973) seems to do fairly well requiring a source cleaning only about every 6 months while running samples about 18 hrs a day. Columns would last about 6 months too.
If you are going to run volatile compounds (e.g., B.P. < that of napthalene) then I would just suggest using a purge and trap concentrator system for water analysis. It is far more sensitive than you will ever get by injecting a microliter of a water sample.
Hope this helps a little.
Ty
