GPC Manual Injection Technique

AnnaB

Hello, 

I am rather new to GPC, and most of my career experience has dealt with HPLC's and GC's that have had autosamplers. However, in my current workplace, our HPLC pump for our GPC setup has a Rheodyne manual injector with a 50uL size loop. 

We have been struggling with inconsistent results on this instrument, and after reading some articles about complete, partial, and over-filling loop filling technique, I found myself wondering if I should try to vary our injection volume in order to achieve better results. 

We are currently using a 100uL injection, which puts us in the complete-filling category.

Any input or personal experience with these varying techniques would be greatly appreciated. 


(Waters 1515 pump, Waters 2414 RID, and Rheodyne 7725i injector)

Thank you very much!

Neil

Hello
Since the manual injector has a fixed loop size, full loop injections will be more reproducible than partial loop injections  I am confused - you say you have a 50ul loop but you make a 100ul injection.  Can you please clarify that point.  Injection should volume should be determined from sample concentration and the number of columns connected in series.  I have attached a slide from a presentation that will give you some guidance.
I hope this helps!
Neil

Neil

Here is the attachment.