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- Posts: 5
- Joined: Wed Mar 29, 2017 12:45 pm
I have been struggling with trying to finish an AR method on GCMS, I was hoping for some advice or suggestions.
I am having several problems:
1. When I run a check standard the area counts have an RSD>5%.
2. The area counts decrease each consecutive run (i.e.: if I prep the std once and run it 3 times from the same vial the area counts for a given compound look like this: 14,707 13,680 12,833).
3. I just changed the gold seal & liner prior to this set of data and had a loss in area counts. For the same compound listed above prior to gold seal & liner change: 18,545 18,115 15,900.
Any help at all would be greatly appreciated, I am pretty new to this type of work. I have included the specs and run conditions below. Thank you in advance!
I am running an Agilent 7890A gc coupled to a 5975C MSD, it has a 2 way CFT with active pressure control splitting between an MSD and an FPD. I just cleaned the source at the beginning of the month and changed the column in September. The column is an agilent DB5 30x0.25x0.25. I am using a splitless liner, running the method pulsed splitless. I am letting the std come to room temp and there is no significant temp fluctuations in the lab.
Oven Program:
45 °C for 1 min
then 20 °C/min to 150 °C for 6 min
then 10 °C/min to 200 °C for 1 min
then 10 °C/min to 260 °C for 2 min
then 10 °C/min to 300 °C for 10 min
inlet:
Pulsed Splitless
Heater On 200 °C
Pressure On 28.55 psi
Total Flow On 63.899 mL/min
Septum Purge Flow On 3 mL/min
Gas Saver On 20 mL/min After 3 min
Injection Pulse Pressure 30 psi Until 1 min
Purge Flow to Split Vent 60 mL/min at 0.8 min