rb6banjo wrote:
That is CO2. You'll see it be quite variable. It just doesn't condense well at the head of the column after injection so it's just a blob. It's going to be very depended on the vapor pressure of the CO2 in the sample. That's probably why you see variability.
A quick look at 8260 (I'm not an environmental-sample analysis guy) it looks like it's for solids - like soils? Is that what you're analyzing ultimately?
CO2 adsorbs to different surfaces/materials quite differently. When you hit it with water, you'll liberate it from those surfaces to various degrees. If you're analyzing soils, this could explain why the CO2 is different from sample to sample.
8260 is a method in SW824 and even though the EPA section is Solid Waste the method is for multi matrix samples (water, soil, solid, sludge, hazardous waste, ect.).
CO2 will definitely be in everything and at varying levels. The only way to ignore it would be to start scanning at 46m/z if using 45m/z you will have a very noisy baseline since it will be hit or miss if the MS detects it at 44 or 45m/z.
CO2 may be a little less evident in Purge and Trap if you are using a dry purge time since it can bleed through the trap unless you are running sub ambient trap temperatures.