The following tutorial describes how signal to noise (S/N) ratios can be estimated from acquired data. Read through the following explanation and then practice the calculations at the end of this tutorial with a partner.
Tutorial: Part 1 – Estimating S/N from a spectrum or chromatogram.
- Find a section of the data that contains a representative baseline (see Figure 1 below). Notice that on the chart, the representative baseline does not contain any signal from an analyte.
- If the data is on a piece of paper, draw two lines that are parallel with the baseline and tangential to the edges of the baseline (see Figure 1). This is the noise.
- Estimate the noise by calculating the difference between maximum and minimum noise signal (e.g., the difference between the tangential lines).
- Estimate the signal by measuring the peak height from the middle of the noise to the top of the peak.
- Calculate S/N.
- Calculate the noise in the chromatogram in Figure 1.
- What is the value of the signal exhibited by the analyte?
- What is the S/N?
- Based on the estimated S/N, can the analyte be reliably detected? Explain.
- Based on the estimated S/N, can the analyte be reliable quantified? Explain.