Chromatography Forum

I try to use my Shimadzu GCMS to do semi-volatiles(ppm level), pesticides(ppb) and volatiles (ppb). Due to the difference requirement on sensitivity, I have 3 columns for these three applications. Currently, I switch columns to do these analysis. However, after 3 weeks, I feel it is not a very good idea since I have to turn off the instrument, change column, and condition the column (sometime take overnight to do it), all of which take me at least a day, no mention I have to redo my calibration curve and sometimes I have to re-install the column due to the bad cut or position the column. I also worry about the contamination of ion source.

Is it possible to have these 3 columns install paralleled and share MS? I can install a new injection ports which I think there are space and ports 3 more injection ports. Or anything I can do to reduce the down time for the instrument due to the switching columns and avoid the bad cut or position the column?

Any suggestion is welcome.

Thanks a lot!

I had 2, guess 3 is possible too, but sensitivity will drop as you will dilute your sample with flow/s from other column/s. So address this.

But you really need more instruments, tell your boss.

Dedicated instruments is the only (good) way. Anyway i'm sure you could use the same column for both semi-volatiles and pesticides, this is better than using the same MS for multiple columns.

You can put an interface into the MS so that you can change columns without venting. Look in the Restek or Scientific Glass Engineering catalogs.

No reason to have a separate semis and pesticides column - use a RXi-5Sil-MS or similar and you'll have more than adequate separation for everything. If you're very careful, and use low starting temps you can use the 5Sil for volatiles - takes some chromatographic skill. Normally you'd want to change columns to run vols - you'll need to change liners anyway, so it's a good time.

Hard to run vols and semis on the same system. I have done it, but you're better off with separate systems for vols and semis/pesticides.

Thanks a lot, for all suggestion. I may combine SVOC with pesticides in one column.