How can i set up a safe method for direct injection of aqueous samples in gcms using a DB-WAX column?

Hello everyone,

I have to inject aqueous samples (mostly hydrolats) in my GC-MS using a DB-WAX column as part of a study on hydrolats composition. 

From my research, I have found conflicting opinions, and I am unable to understand what the correct injection parameters are to avoid backflush or mass detector issues.

Is anyone so kind to try to give me the right hint to follow the correct way to perform this injection safely?



  • Injecting water is rarely a good idea and requires a bit of extra consideration.  1 µL injected is approximately 1000 µL of vapor and most liners are only about 800 to 1000 µL.  This means that the reproducibility is suspect and the injection port plumbing gets contaminated by sample residue in the tubing away from the heated zone.

    In MassHunter Acquisition on the GC parameter screen is GC Calculators. Use the Vapor Volume calculator, enter the necessary parameters, and see the results.  Do not exceed the available volume in the liner - the box will turn green if the sample vapor will fit.

    You will either need to inject maybe 0.5 µL or less, change to a pressure pulsed injection mode, or change your solvent to one with a lower expansion coefficient.

    Upload the acqmeth.txt file that is located in Windows underneath your run method subdirectory (xxxxxxx.M)  so that further recommendations can be made.

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