Chromatography Forum

Hello,

I have a method developed in 2000 that used a Shimadzu GC17A. The method uses a 0.32 mm ID capilary column and injects a liquid sample. The method states an injection volume of 0.5 uL and the injection type as "direct inject". Can anyone explain what the injection type, "direct inject", is? Is it the same as a splitless injection? I'm thinking this might be it since the method doesn't list any split ratio. I do not have any experience with this or any Shimadzu GC.

Thanks for your help.

That's what it means.

A direct inject means the split and purge vent is closed and stays closed. A splitless injection just has the split vent closed during injection with the intention of being opened back up later during the run.

A direct inject means the split and purge vent is closed and stays closed. A splitless injection just has the split vent closed during injection with the intention of being opened back up later during the run.

Keeping the split closed all the time is poor practise with no benefits compared to a split-splitless injection with the proper splitless time.

"Direct injection" is one of those terms that has been misused so often that it has become meaningless. It originally applied to packed columns when sample was injected onto the actual column rather than into a separate injection volume. Logic transferred it to on=column injections with capillary columns, but it was then mis-used to mean splitless injections.

dlbenach, unless your GC has an on-column injection port then direct injection means splitless.

Peter