Chromatography Forum

I am running a headspace GC-MS method similar to USP <467> for the analysis of volatile solvents in a polymer. When processing the data I get very different results depending on whether I use the RIC (reconstructed ion current) versus the Quant. Ion (m/z=73 for Methylethylketone). I am using external calibration with 3 calibrants. The results are 73 ppm MEK with RIC and 205 ppm with Quan. Ion m/z=73. Does anyone know how to explain this? Is there any guidelines for using RIC versus Quan. Ion for quantitative results?

Thanks in advance.

Regards,

Chris

In the RIC mode the detector acts as a universal detector. It is possible that something is co-eluting with your analyte which will affect the results. In the SIM mode it is possible that this co-eluting substance becomes invisible to the detector, so you may get different results.

One more thing- I don't understand why you are looking at 73- is this a typing error? The MW of your analyte is 72, which means you would be looking at the carbon 13 isotope peak of the analyte!!!!