Chromatography Forum

Hello,

I have had some repeatability issues and higher than expected quantitative results as of late. I am running a splitless injection method on Agilent GC-MS single quad. This method has only three peaks of interest. Tautomers allyl-isothiocyanate and allyl thiocyanate with 2-undecanone IS. There is no sign of column bleed. I have significant peak fronting and have been told that the counts I'm seeing are high/consistent with overload by tech support.

I have clipped the column quite a few times, so I am wondering if shortening a 30mm column by a few meters (maybe 2) would cause a significant change in capacity. Inlet maintenance has been done. I don't want to throw away a perfectly useable column if I can avoid it. I am currently injecting at 10% of the syringe volume, so decreasing the injection volume is not an option without buying a new syringe.

Any ideas?

In the past, were you able to run those compounds at the same concentration without the fronting?

Does it go away if you run your standards / samples at a low concentration?

I am running a splitless injection method

I have significant peak fronting and have been told that the counts I'm seeing are high/consistent with overload by tech support.

I am currently injecting at 10% of the syringe volume, so decreasing the injection volume is not an option without buying a new syringe.

Any ideas?

Girl - here's my initial thoughts:

1. I would look into split injection instead of splitless.

2. I would get my pointy-haired boss to spring for some smaller-capacity syringes.