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Chemistry LibreTexts

Signals-to-Noise Ratio

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  • 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.

    1. 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.
    2. 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.
    3. Estimate the noise by calculating the difference between maximum and minimum noise signal (e.g., the difference between the tangential lines).
    4. Estimate the signal by measuring the peak height from the middle of the noise to the top of the peak.
    5. Calculate S/N.
    Figure 1. LC-DAD chromatogram.


    1. Calculate the noise in the chromatogram in Figure 1.                                    
    2. What is the value of the signal exhibited by the analyte?                                    
    3. What is the S/N?                                    


    1. Based on the estimated S/N, can the analyte be reliably detected? Explain.


    1. Based on the estimated S/N, can the analyte be reliable quantified? Explain.


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