Developing method for Nitrosamines with single quad

[devilrejects2020]

Good afternoon

I am developing a method to determine nitrosamines using Headspace - GC - MS with single quadrupole.
I would like to know if the following conclusions I reached are correct:
- The concentration of the sample is directly proportional to the number of points obtained for a certain peak: As the concentration increases, the number of points increases and it looks more defined.
- The Dwell Time and the Split are inversely proportional to the number of points of the peak: By increasing the Dwell Time and the Split, the number of points decreases.

Also I would like to know if the Gain Factor affects the noise signal since I noticed that when trying to increase the number of points in the peak by reducing the dwell time I can only reduce it to 120 ms, a shorter dwell time provides a more defined peak with more points but with much more noise, does that mean that to reduce the dwell time to a minimum I must reduce the gain factor to a minimum? I currently use a gain factor 15.

[JMB]

You need to be very careful that you use the correct terminology with this type of question.

1) The number of data points across a chromatogram of an analyte determines how well the peak shape is defined; 6 will give an approximately gaussian ("normal") peak shape, while 16 (26, 36,... ) will give a much more well-defined peak shape. This is critical for accurate quantitation!!

2) The number of "counts" recorded by the data system is directly proportional to the mass of analyte that reaches the detector. The counts give the signal for that analyte, and it is the signal-to-noise (S/N) ratio that determines whether an analyte is (a) detectable, and (b) quantifiable.
Usually, S/N greater than or equals 3:1, for (a)
10:1, for (b).

James Ball is much more qualified than I to answer your question.

[James_Ball]

Just a little more information needed to really determine how we can help.

When you mention split, are you talking about the inlet split ratio?

If so, the higher the split ratio the lower the mass on column and the lower the sensitivity you will have.

With more modern GCMS, you can set dwell to as low as 5ms and still have about the same sensitivity as 50ms, but at 50ms you will have more samples per mass which will give a more stable signal. Longer dwell times don't really increase sensitivity or counts per second, just lets you average more replicates which averages out some of the noise and instability.

Are you working at what is the limit of detection or working with an amount on column that is able to give a strong signal? Also how many masses are you acquiring in each time segment and what is the dwell time for each mass in the time segment? These settings will determine how many times you acquire each mass within a certain amount of time which affects how many points per peak you will have at a given chromatographic peak width.