I need to do trace level analysis of BTEX with a GC/FID down to 1 ppm. The problem I keep running into is that my samples are all in 40% n-Butyl acetate (can't change that since they come into the lab this way). Since n-BAc is so volatile to the point that when I use 1 mL of sample in a 20 mL HS vial heated to 80 for 15 min the n-Butyl acetate I believe over saturates headspace suppressing my BTEX. Any suggestions would be appreciated.
You can extract it from n-BAc matrix by dispersive liq-liq micro extraction or solid phase then analyze it with gcfid to remove media. Also, can I ask that if you tried direct analysis or not (direct injection; without headspace or thermal desorption etc).
A few crucial informations are missing in your request: what's constituting the 60% of your sample? which column and chromatographic parameters are you using?
Classical headspace is almost impossible with such an amount of volatile solvent, I suggest you to try to inject your sample directly (split injection).
The other 60% consists of polyester polyol. Currently I am using a RT-1701 column. The high viscosity and sticky nature of my samples would lead me to diluting the sample for injection lowering my concentration even lower. I was under the impression that a direct injection method would be less sensitive and unable to see 1ppm. Any suggestion on extraction methods?
When you mentioned the concentration is app 1ppm I assume it was the final concentration. If your sample has a high viscosity and you need to dilute it, seems like you need first an extraction then direct injection. I am not sure but you can do a literature scan what other scientist employ to extract BTEX from the similar matrices. Liquid-liquid micro-extraction can do the job. You can determine the extractant according the affinity between your sample and the nBAc matrix.
regards
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