Chromatography Forum

Hi to everyone ,

I’ m not an experienced gas chromatographer and want to test PEG 400 according to USP 34 official method. One of the items is the limit of EG & DEG.
Method use a packed GC column with sorbitol as stationary phase. My GC is Shimadzu 17A ver.3 and I only worked with cap columns. In the past when I faced a method that used a packed column, switched to capillary equivalent. I’d be grateful to help me about these questions.

-Why there is no cap equivalent in this case?
-How can I find a similar phase like sorbitol (polarity; etc) in capillary columns?
-What is difference between split/splitless injector and WBI injectors?

-Why there is no cap equivalent in this case?

Because the packed column does not contain a liquid phase. Therefore it is impossible to coat the hollow tube with the dry powder used in the packed column and get it to stay put inside the tube.

-How can I find a similar phase like sorbitol (polarity; etc) in capillary columns?

Because it is not a liquid phase you cannot find a phase in capillary columns like it. It is possible to make something comparable. But I doubt it will be easy and I expect you will have to make it yourself, as no one will want to expend manpower and overhead to make an experimental column of which they will only sell ONE copy to you.

-What is difference between split/splitless injector and WBI injectors?

The WBI injector is an injector where there is no outlet other than the column itself. The split/splitless injector has an outlet which is programmable which allows the sample to leave the injector without exiting through the column. With the WBI the sample may ONLY exit through the column.

best wishes,

Rod