On-colulmn injectors

Chromatography Forum: GC Archives: On-colulmn injectors
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Steve on Friday, February 11, 2000 - 03:06 am:

Hi all. We have recently installed an on-column injector on one of our GCs (HP5890). The injector installed is for capillary columns. We now have a method that specifies on-column injection with a packed column. Is it possible to use a packed column on the on-column injector? Is there an adapter that can be used? My first thought is no. Can anyone prove me wrong?

Thanks for the help

Steve


Top of pagePrevious messageNext messageBottom of pageLink to this message  By David McCalley on Friday, February 11, 2000 - 04:03 am:

Steve,
You do not tell us what the original injector installed on the HP5890 was, or whether it is still there? If it is a split/splitless injector, then the best way to do packed column on-column injections is to purchase a packed column with a long injection inlet (this is different from the standard HP packed column). The long injection end of the column replaces the glass liner used for capillary injections. It feeds right up into the injection port allowing on-column injections. If I remember rightly, all the nuts you need to do this are in the kit supplied originally with the 5890. The HP 5890 was actually designed to allow you to do this. I could see that it might be possible to bodge some adaptor, but the capillary on-column injector was never designed for use with packed columns.
I am not an HP engineer and you should verify this information with them.

David McCalley


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Beppe on Friday, February 11, 2000 - 08:53 am:

David is right; moreover, if your 5890 has (had) a packed/megabore inlet, it is simpler, you just have to remove the steel inlet (in the oven) and to fit the long end of the glass column with a Vespel or graphite/Vespel ferrule and a 1/4 nut; if it is a split/splitless inlet, you will also have to plug the split line.
The initial question is : what do you call "on column injection" ? It generally considered as depositing a liquid sample directly on the inner walls of the colum and then vaporizing it later; to do this, the needle must fit closely the column diameter; this is why it is only possible with a capillary column.
Injecting "directly" in a packed column can only be a traditional heated injection; the only advantadge is that it avoids contact with metal parts for very senssitive compounds


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Scott Fredrickson on Friday, February 11, 2000 - 12:11 pm:

This sounds like a method that was developed on old equipment and needs updating. Unless you MUST follow it, I'd suggest adapting it to a split/splitless or megabore system. More than likely it will work just fine on a standard modern system.

More details, such as compounds, levels, column type, detector, etc. would be helpful in evaluating the odds and time required for upgrading.


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