Direct Aqueous Injection

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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Hello everyone,
I'm quite new about this GC world but I need to measure Tetrachloroethylene (PCE) and Trichloroethylene (TCE) mixture (or one by one) in GC. I tried several times with MS and FID but I got meaningless results, I still do not have a calibration curve. Samples for MS were prepared with hexane extraction from aqueous solutions and aqueous samples diluted from stock solution directly injected to GC/FID. We have headspace unit but out of use and I should immediately measure them with what we have. Am I wrong about sampling of these chlorinated solvents if yes could you please inform me about sample preparation of PCE,TCE for MS and FID or I use wrong column type with wrong method ?
The FID column is Elite-FFAP (30m,0.32mm,0.25um)-(40 to 250 degree C) and
MS column is DB-5MS (30m,0.250mm,0.25um)-(-60 to 325/350 degree C) also Elite-5MS column we have.
thank you in advance
Chlorinated solvents won't have much response on an FID, they don't burn well.
For your extraction solvent try dichloromethane, it boils at a lower temperature than hexane.
For a quick reference on MS analytical conditions try: ... 3-2017.pdf

A DB-5MS column won't have good retention for those compounds so it's good you can cryo cool your oven.
The 5ms column will work if you start with an oven temperature of about 30-35C with a 1-2 minute initial hold time. A 624 phase column would work better and also need a thick film 1um for a 0.25ID column. If 0.25ID I prefer a 40m column for separating the volatile compounds, 0.18ID is even better, since it gives you more initial head pressure to contain the solvent expansion.

Definitely use Methylene Chloride(Dichloromethane) instead of Hexane as hexane will co-elute with a large solvent peak closer to the targets, and if using FID will be very large compared to response of the chlorinated analytes.
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