Variation in results

[catrinaf]

The products we make are methacrylate monomers which contain an azo-based polymerization initiator. We need to determine how much initiator is present. A calibration has been set up using different concentration levels of the azo initiator, and the peak area represents a certain percentage. We don’t use an internal standard

[Peter Apps]

Please give the details of how you did the calibration - what you dissolved in what, how you did dilutions, the range and the r-squared, and the repeatability if you have determined it.

What is the signal:noise of the peak that you are interested in ? Can you post a chromatogram - instructions are in a sticky at the top of the LC forum page.

Is the initiator stable at GC temperatures ? if you add an intrnal standard with a similar MW do you also get poor repeatability for its peak area ?

Do you have to use acetone as the solvent, or could you use something with a higher boiling point and higher MW ?; the pressure pulse that you get when acetone hits the inlet at 300C could be the cause of the poor repeatability.

Peter