Location:

Report Variable (Peak Results)

Default:

Current sample; time interval: n times the width at 50% of the peak height

Related Variables:

Height, Signal Noise

Description:

The Signal-to-Noise Ratio peak variable indicates the quantification accuracy of components.

The Signal-to-Noise Ratio is calculated as follows:

The value for PeakHeight always corresponds to the related value of the peak variable Height (‘peak.height’).

Signal noise calculation in Chromeleon is based on the ASTM method. For calculation details, also refer to Signal Noise ('chm.noise').

The following figure shows the relation of peak height and signal noise:

Parameters:

You can select the sample used for calculation. In addition, you can define the time interval used for calculating the noise.

Current Sample

(default) The noise is calculated for the current sample. The system selects a peak-free time interval to the left and/or right of the current peak as close to the peak as possible. If Chromeleon finds two suitable intervals, it calculates a value for each interval. The larger of the two values is then used to calculate the noise. If Chromeleon cannot find a peak-free time interval with a suitable width on either side of the peak, it cannot calculate the signal noise.

Blank run settings of corresponding QNT method

Select this option to use the blank run settings from the General tab page of the QNT Editor for calculating the noise. The time interval is situated equally to the left and right around the retention time where the peak of interest would be found.

Recent blank run in current sequence

Select this option to use the most recent blank run in the current sequence for calculating the noise. The time interval is situated equally to the left and right around the retention time where the peak of interest would be found.

Fixed sample:

Select this option if you want to calculate the noise for a fixed sample.

Use <nn> times the …

The time interval corresponds to n times the width at 50% of the peak height . or n times the width at the base line.

Use a fixed interval

A user-defined, fixed time interval is used for calculation.