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- Posts: 2
- Joined: Wed Oct 18, 2017 4:46 pm
A calibration curve is prepared using Accustandard M-525-REF-EA-5x, lot#220101139 by preparing a 20 ppm stock and then using this to prepare a 9 point calibration curve ranging from 0.02 - 5.00 ppb.
GC-MS maintenance has just been performed (sources was cleaned with Al powder+MeOH mixtures and then rinsed with water, acetone, acetonitrile, then MeOH). A new Restek column was installed (RXI-5ms, 30m, 0.25mm ID, 0.50um DF) and tune check came back looking great.
Injection parameters are 1uL @275C, pulsed splitless, pulse pressure 30psi for 1min. Oven ramp is 70C for 1 min, ramp 25C/min till 200C then 10C/min till 320 then hold for 3 min.
All analytes in the absolute spike are coming back at 1ppb except simazine with is doubled. My only explanation is one of the standards I am using (accustandard or absolute) may not have the correct simazine concentration or has degraded. We are keeping both products away from light as much as possible and sonicating as suggested by the manufacturer prior to use.
If anyone has suggestions on why only simazine differs I would appreciate the discussion. Thank you.