Chromatography Forum

I have a silly question about area counts:

i am using SIM mode and I am searching for two ions in one group (Benzene group with m/z 77 and m/z 78 becasue they are most aboundant fragments). In the chromatography, time is my X-axis and aboundance is my Y-axis. And I have two peaks there at different time. When I right click the peaks, the m/z spectra showed 77 and 78 for both peaks with different heights of 77 and 78.
Why do I have two peaks? What are they?
And how do I know what area counts I have for this sample? Do I need to add up the area counts from both peaks or just take the biggest one?
Also, I found that, one of the peaks diminishes when the smple concentration increases. Why is that?

Thank you so much! Have a good one!

Hong

A more extensive explanation of your analysis would be preferable to give you a more precise answer (i.e. are the fragments used to discriminate between different substances? Two masses in one group, what do you mean? Or any other valuable info) but I'll try to guess something:

1) if you're acquiring in SIM for both the masses all the time, it's correct you see both the masses in your peaks;
2) if you're acquiring both the masses to reach a better sensitivity, you need to sum their intensity;
3) if you're acquiring them as a discriminant between substances, you need to separate the peak areas.

And so on.