Chromatography Forum

I am trying to set up a headspace evaporation residual solvent method using a GC/MS but I an trying to figure out how to calculate the final concentration of the cannabis residual solvent. For starters, I am using 200 mg (0.200 g) of plant material and adding 1 mL of 2,2-dimethylacetamide (DMA). From that mixture, I take 5 uL and add it to a 20 mL headspace vial and analyze it. Is the final calculation the instrument value in ug/mL multiplied by 0.005 mL (5 uL) divided by the 0.200 g weight if I want the units in ug/g?

For starters, I am using 200 mg (0.200 g) of plant material and adding 1 mL of 2,2-dimethylacetamide (DMA). From that mixture, I take 5 uL and add it to a 20 mL headspace vial and analyze it.

Are you dissolving your analyte? It's not flower, because there's no reason to look for solvents in vegetable material. So you must be looking at concentrates.

1 mL of DMA + 200 mg of dissolved concentrates is going to give you a different volume, increasing your error substantially.