Hi everyone,

I have a discrepancy with some data I've retrieved using Empower 3. Maybe someone can enlighten me on a more logical approach to this. Note this might be an issue with Empower 3 and not so much my GC, but I've checked calculations manually and they match Empower's. Sorry if this is posted in the wrong forum.

My task was to calculate the weight percent of acetonitrile in a solution via GC. I went about doing this as I usually do:

I made a standard of 0.01% (v/v) acetonitrile in DMAC. This was done through a serial dilution, 1 ml acetonitrile in 100 ml solvent, then 1 ml of this solution into another 100 ml of solvent. I enter the standard amount as 0.0786 mg/ml into Empower under components. Acetonitrile is 786 mg/ml, so divide that by 10,000 due to the dilution.

My sample had a density of around 880 mg/ml. I prepared this very similarly to the standard, although only a 1,000x dilution. This was done by taking 1 ml, diluting to 100, and taking 1 ml of this solution and diluting to 10. This information was entered into Empower as sample weight = 880, dilution 1,000.

The thing is I'm seeing about 20% wt. acetonitrile when there should only be 10% or less. I re-prepared both the sample and standard, all numbers are nearly identical each time for multiple injections, i.e. area counts, retention times, etc. The integration looks fine.

The area count for the standard is about 10, the sample is around 22. As far as I can tell I have entered all my numbers correctly, and the preparations are very consistently returning the same values. I know I've done the preparations properly so you can take that for granted.

Is this an instrument issue? I can provide more specifics as I'm sure I'm leaving things out. It's just that the chromatography looks absolutely fine, and my data entry seems correct. It would be very unlikely that this sample is in fact 20% wt. acetonitrile. Thanks for any input.