wf.callahan wrote:
I'm actually pondering the same question today. We frequently use a guard column as the "transfer column" from the capillary to the MS. It does save us time when switching between columns for different analyses. Does it matter what size ID the columns are? If I'm using a .25mm capillary column with a .32mm transfer column, will I encounter any chromatographic problems?
Shouldn't be any problems, especially with larger transfer lines. I was using a metal Y connector to join two columns to a transfer line into the MS, but was having trouble getting the proper flows through the column. For that I had to use a 0.53mm transfer line with the two 0.18mm analytical columns, this allowed the end of each column to operate under vacuum instead of at an elevated pressure do to restrictions into the MS. With a single column it shouldn't matter.
The Restek adapter listed previously uses a 0.1mm transfer line to cause a restriction so that you can change a column without venting because it creates enough restriction that the flow into the MS is low when the column is removed, but I would still cool the source before using that method just in case.
I have also installed transfer lines before when I wanted the temperature of the interface to be higher than what the maximum temperature of the column phase was, to prevent the phase from bleeding into the source, that works good also.