# MassHunter S/N

Question asked by plfaria on Aug 11, 2020
Latest reply on Sep 9, 2020 by howard_sanford

Hello,

On company that I work, in Portugal we have a GC-MS with MassHunter software.

Since the implementation of the software for the GC-MS we are manually using the formula below for the calculation of the EP signal to noise:

S/N = 2 * ( Noise of Raw Signal LOQ / Noise of Raw Signal Blank)

For the Noise of raw signal we use values given by the software and it is used the same region of noise both for blank and standard/sample injection.
When we compare this approach with other software’s it is not clear some points and we could not find the answers in the Agilent manual.

Can you please give us support on the questions below?

1. By default the software uses a noise SD multiplier with a value equal to 5. (It is possible to change at least between 1 and 5). This factor does a direct multiplication to the NRS value calculated. Why the default value is 5? What means?

2. What is the difference between the peak height and the NRS?

We are considering about changing the approach from NRS to use Peak height instead, however, we still need to know which value of noise SD multiplier we should use because it will make a big difference on blank noise, and doing that, we are considering to use this formula:

S/N = ( 2 * Peak Height ) / Noise of Raw Signal Blank

It seems logical to you, doing this "change" and update the way that we calculate S/N?