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- Posts: 3
- Joined: Tue Jul 31, 2018 4:43 pm
I'm new here, and I have an issue with GC.
I'm working on an alcoholic beverage, and I need to have a standard curve to determine how much ethanol and methanol is in the beverage.
Well, I prepared standard as follow;
45% ethanol, 0.05% methanol and the rest is water.
40% ethanol, 0.1% methanol and the rest is water.
35% ethanol, 0.15% methanol and the rest is water
(ethanol is 100%, methanol is 99.99% pure)
Agilent 6890 GC with an autosampler.
HP-5 column, 30m.
Inlet temp: 175C
Oven temp: 40C for 3 mins, then to 80C by 10C increase, wait 3mins, then to 120C by 10C increase, wait 1min.
Split ratio: 40:1
Injection volume: 1 ul
I have irreproducible areas even from the same vial. Let's say, I have 4500 area, then 15000. and vice versa.
What would be the problem having such fluctuation?
Thank you.