Chromatography Forum

Hi sample loop size is the lenghth of the loop or diameter? what size of sample loop should be chosen when using a small syringe (25ul)? thanks

Sample loop size refers to its volume and its chosen mainly in relation to the internal diameter of the separation column used, but also sample concentration, sensitivity requirements etc...

Sample loop size refers to its volume and its chosen mainly in relation to the internal diameter of the separation column used, but also sample concentration, sensitivity requirements etc...

when using a 25ul syringe, is a 100ul loop size better to use than a 250ul loop size?

It's always best to use a syringe that is 4 times or so bigger than your loop, so it looks like it is time to invest to a new syringe. Maybe you should give more info on your experiment and what you really trying to achieve...

The idea behind this is that you don´t get injection volume variation due to laminar flow or syringe filling variation. The extraordinarily skilled still may manage to get an injection variation in there, via air in the syringe. If it is important to inject the same amount each time, one should check that.

In the ancient past when I did manual injections, I was always more comforable using a sample loop of the volume I wanted to inject (e.g. 10 microliters) and just flushed through, the theory being that it would be impossible to overload and inject more than 10 microliters. So I always did full loop volume injections. Yes, changing the loop size was a hassle.

Hi chromochat

Simple question - what volume of sample do you want to inject onto the column ?

Peter

Here is a link to the instruction manual for Rheodyne injectors. It explains partial-loop and full-loop injections.

http://www.idex-hs.com/support/rheodyne ... 20157D.pdf

I also suggest that you search for injection techniques on the LC.GC web site. I'm sure that there is an article on manual HPLC injection technique.