Chromatography Forum

I was told by our Instrument supplier that MSD Temperature should be roughly 50 °C below the final temperature of the GC program.
However I have seen several methods for GC-MS where the MSD temperature was the same as the final temperature of the GC program.

Any suggestions/ideas what the influence of the temperature on the analysis could be?

I have experimented with source and quad temps on the Agilent MS and once you start getting up to the 250C range on the source I have seen higher background noise with lower overall sensitivity. I normally run in the 200-230C range on the source temp and 150C on the quads. Hot enough to keep moisture and crud from hanging around and cool enough to keep sensitivity up and noise down.

As for the interface temp, keep it below the max isothermal temp for the column phase, otherwise you will be cooking off stationary phase onto the source which will lead to needing to clean it more often. If you need higher interface temps then you will have to run a short piece of uncoated guard column attached to the end of the analytical column to avoid problems.

If you need higher interface temps then you will have to run a short piece of uncoated guard column attached to the end of the analytical column to avoid problems.

in order to avoid extra connections close to the ms, which are not always easy to leak-check, we use a restek integra guard column http://www.restek.com/catalog/view/577 and use the 'pre-column' part as transferline from the gc to the MS. This way we avoid (minimize) having column bleeding reaching the MS

If you need higher interface temps then you will have to run a short piece of uncoated guard column attached to the end of the analytical column to avoid problems.

in order to avoid extra connections close to the ms, which are not always easy to leak-check, we use a restek integra guard column http://www.restek.com/catalog/view/577 and use the 'pre-column' part as transferline from the gc to the MS. This way we avoid (minimize) having column bleeding reaching the MS

That is a great idea!

we are using Agilent 7000b MSD and we are using the method given in Agilent pestanalyzer.In that last oven program temperature and transferline temperature is 280 Source temperature is 300 and quad temperature is 180.Is this cause this any problem in sensitivity.

A hotter source temp can result in greater fragmentation; the molecular ion may be less intense. I am not sure if it ends up being a huge loss, it likely varies by the molecule.

we are using Agilent 7000b MSD and we are using the method given in Agilent pestanalyzer.In that last oven program temperature and transferline temperature is 280 Source temperature is 300 and quad temperature is 180.Is this cause this any problem in sensitivity.

You can do a test by running the same sample with a source setting of 150C, 200C, 250C and 300C and compare the sensitivity to see what the effect of temperature is on your specific analysis. Hotter temps can keep the source cleaner, but I have also found that I see higher noise and background when running higher source temps.

Thank you for your replies

If I find some time I will test different source temps to see what's happening