When I used GCMS to analyze phthalates in tobacco, I encountered the following problems:
1.response dropping;
2.calibration curve is quadratic not linear;
I tried increase the temperature of inlet, transfer-line and ion source, but it did not work .
Maybe the phthalates is retained in the GCMS system?
How to resolve this problem?
Jiangtao,
it should be linear.
What is the concentration range of your calibration standards?
Do you use SCAN or SIM mode?
Maybe the concentration is too high and the PMT(what is the PMT voltage?) is obtaining a saturation? if the sensitivity is too high you can lower the PMT voltage (try with 100V lower value).
regards,
GB
Grzegorz Boczkaj
Hi Grzegorz,
Thank you for your answer.
The concentration range is 0.02mg/L - 20mg/L . and the split ratio is 10:1
I use SIM mode.
I can't modify the linear range and split ratio because this is what the customer wants.If I turn the PMT down, it may be less sensitive.
The standard curve is like the attachment I painted.
lower the PMT and check if you are able to detect the lowest calibration point. If you obtain reproducible results - use this settings and check the linearity.
regards,
GB
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