Chromatography Forum

I am thinking about moving from a .25mm column to a .18. Would I have to actually change anything other than the column info in the method? Will the EPC simply work out the pressure differential on its own? Also, any ideas on the increased likelihood of overloading the column?

What the gas controls can and will do depends a lot on what kind of GC you have.

The "loadability" of a column depends on the cube of the diameter; the 0.18 mm column will overload with between a third and a half of what you can put onto the 0,25 mm.

Peter

My instinct response is that column loadability depends on the amount of stationary phase of the column. If you keep the phase ratio the same for a 0.25 mm i.d. column and a 0.18 mm i.d. column, then the overlaod limit of a 0.18 mm i.d. column is about 52% of 0.25 mm i.d. column.

If you don't keep the phase ratio the same, it is possible for the 0.25 mm i.d. column and 0.18 mm i.d. column to have same loadability by increasing the thickness of the stationary phase for the 0.18 mm i.d. column.

As always use Agilent method teanslator software to figure out the parameters for the new column. EPC doesn't do it for you.

There are a few other aspects to consider.

Upside is less flow into you mass-spec.

Downside, if you're using a pulse-type injection, for an equivalent transfer from the inlet to the column, you'll need more head pressure during the pulse. Verify that you have sufficient line pressure for the pulse.

Greg