Using this method, the application calculates the S/N as follows:
The following figure shows the relationship between peak height (H) and signal noise (h).
The application calculates the time range for the noise determination based on the peak width at half height (w) and a user-defined factor (n). By using these values, you can find ranges free of peaks and inhibit integration regions before and after the current peak in the chromatogram; the inhibited regions have total lengths of at least length w to length n × w.
The application determines a potential noise range with one end point being the main peak and the other end point being one of the following:
- The start point of the next peak
- The start of the next inhibit integration region
- The end point of the chromatogram
- The point where the upper limit for the noise range of n × w is reached.
If the length of this noise range is greater than the width (w) of this noise, the length is used to estimate the noise on the right side of the peak; otherwise, the previous step is repeated at the end of either the next peak or the next unresolved peak group until a sufficient noise range is found or until the end of the chromatogram is reached.
A mirrored version of this search is used to estimate the noise range on the left side of the peak.
Of these two estimated noise ranges, the application uses the larger range to continue the S/N calculation. If the application only calculates one noise range, it uses that range for further S/N calculation. If the application does not calculate either noise range, it returns this message: NA.