Chromatography Forum

Hi,all
I did the gas chromatography experiment. and after that, our superior asked us to finish the common questions about this experiment. However, I do not know the answer. can someone help me with that:

following questions:

why do the different peaks appear under the condition of same sample and same injection volume？
why the peaks do not appear sometimes?
I want to know the answer. thanks.

They are poorly worded questions.

1) I presume that he/she is getting at the chromatographic process. When you inject a sample that has many components, the reason you see many components at the detector as a function of time, is the chromatographic separation that occurs on the column.

2) Peaks will not appear for various reasons:
a) Analyte is not amenable to GC analysis (stays in the injector).
b) Analyte coelutes with another component of the mixture (masked under something else).
b) Analyte does not respond in the detector you're trying to use (e.g., carbon dioxide will not respond in a flame ionization detector).

Question 2) is a little more straightforward than 1) but both could be worded more strongly. Good luck.

The answer to both questions is:

Operator error

Peter