Air blank vs solvent blank.  Can anyone tell me if there is a difference in shooting an air blank vs a solvent blank on an Agilent 7890 or newer GC.  We shoot solvent blanks to ensure that our solvent used in extractions is not contaminated, but was wonde

Air blank vs solvent blank.  Can anyone tell me if there is a difference in shooting an air blank vs a solvent blank on an Agilent 7890 or newer GC.  We shoot solvent blanks to ensure that our solvent used in extractions is not contaminated, but was wondering if it is analytically incorrect or physically hard on syringes, columns, etc. to shoot an air blank in between samples as opposed to an actual solvent blank. The air blank would be an empty autosampler vial. This air blank would be injected on the instrument to ensure there is not carryover between samples.  Since the solvent blank (generally MeOH) is mostly volatilized and there is no actual liquid going through the column, it seems to me that it would be reasonable to use an air blank in between samples, but wanted to get an expert opinion.

  • I can't see a problem with doing an air blank, although if you're just wanting to check the instrument is free of contamination then you could do a "non-injection" blank - if you just leave the vial position empty then the method will run without the autosampler doing anything.

     

    It's worth pointing out that most methods specify a solvent blank - this is a better assessment of whether there's contamination in any part of the process.

  • jerrysmith - performing an air blank does put more stress on the syringe as solvents will lubricate the inside surface of the glass and plunger.  Also injecting air will introduce oxygen into the column, if the column is hot this can degrade the stationary phase.  But the volume of oxygen in a few microliters is very small and will not be significant enough to cause enough column damage to notice in the short term.  If you are going to inject an air blank, make sure the sample pumps in the method are set to zero to avoid unnecessary plunger strokes.

  • I will mark this as assumed answered due to its age, feel free to update us with what you found or post again if this is still an issue.

    Regards

    James

  • This question has been marked as assumed answered.

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