Type of GC Injection to use

[Hanna]

What is the different between these injection method:

On Column injection
Direct injection
Split/Splitless injection
Split injection

How do you decide which one to use or do you just follow literature?

[skunked_once]

What is the different between these injection method:

You will have to do some reading on the various types of injection techniques. You can start here.

http://www.dsbscience.com/freepubs/fore ... ode34.html

Also search the LC.GC web site for good information.

http://chromatographyonline.findanalytichem.com/

Perhaps others will suggest some of the excellent GC reference books available.

[skunked_once]

How do you decide which one to use or do you just follow literature?

It depends. If you are just following a specific application, you can follow the details of their method. If you are developing a new method or trying to improve an existing method, you will need to understand the different techniques. Even if you are using an existing method, it is important to understand why a certain injection technique is used and to be able to troubleshoot when problems arise. Learn what you can and ask more questions

[Consumer Products Guy]

We use split injection 95% of the time, for both GC and GCMS.

[chromatonewbie]

Split injection is not appropriate for samples containing mixtures of widely different compounds, or unknowns or natural/complex samples. Unless you are doing a lot of routine analysis of known compounds it is often better to dilute a sample and inject it splitless. Especially if you want quantitative results.

There are two quite good books you should look at:

Handbook of GC/MS fundamentals and applications (Hans-Joachim Hübschmann) 2009, and
The troubleshooting and maintenance guide for gas chromatographers (Dean Rood) 2007

cheers
Liz

[Don_Hilton]

And just to add to the collection of replies - I use amost exclulsively splitless injection because I do trace analysis.

Hanna,
Do you have a specific problem you are working on. Injection techniques and methods cover a lot of territory.

[Hanna]

I am using direct injection, split, and on column injection using our current method for different analytes.
I wanted to know the purpose of using these different type of injection.

Maybe it is because of the type of analyte and the instrument use.

Thank you everyone for your respond.

I will look into those literatures.

Hanna