Hello,
I’m new to GC machine and I have some issues. We have GC-FID 7890A and using ChemStation G1701EA E.02.01.1177.
Method:
Method: inlet: 250°C, Split: 1:50 with a column: HP-Plot/Q (19095P-QO4) 30m x 0.530mm
Helium is carrier gas
Oven starts at 100°C with a hold time of 0.5min, goes to 200°C in 3min. I also tried isothermal at 150°C
Detector is at 350°C
Sample: 0.1 – 1 µl methanol (tried mixing with heptane as well )
First, the GC software (which I believe only control the GC machine) shows me an unusual plot whenever I run a test (Test plot) as shown in image_1. I see those almost consistent peaks all the time whenever I run a sample (in this case methanol) and even when I have no sample!!. I don’t think those peaks are related to the retention time of my sample at all.
When I tried to look at the data using “Data Analysis” software, I was able to see the response vs retention time, but again I also have a problem here. Every time I inject the sample, I’m only seeing noise. Today, I was luck to inject methanol ~1 µl using a syringe and got a peak at retention time ~ 1.2 mint as shown in image_3. After that, every time I inject the sample, I’m only getting noise (image_4).
I tried to change some of the parameters as follows:
Sample volume : 1 -5 µl (tried ethanol, methanol)
Injection temperature: 250 °C split mode (varied split ratio from 2:1 all the way to 50:1)
Overn temperature: 50 – 150 °C isothermal (tried to vary temperature from 50 to 150 °C )
Detector temperature: 350 °C (kept constant )
I don’t understand why I got one good data set (image_3) after that regardless of what I did, all what I’m getting is just noise. If you could provide some guidance, I would really apricate it.
