In Signal to noise ratio, it says to calculate SNR based on blank injection. How can I calculate on blank injection if I don’t know about the analyte peak? Can anyone explain it, please?
Please refer to the below text reproduced from USP chapter <621> Chromatography- Signal to Noise Ratio calculations.
It is clearly specified that the range of the noise in a chromatogram obtained after injection of a blank (Figure 7), observed over a distance equal to 20 times the width at half-height of the peak in the chromatogram obtained with the prescribed reference solution and, if possible, situated equally around the place where this peak would be found. If a baseline of 20 times the width at half-height is not obtainable because of peaks due to the solvents
or reagents, or arising from the mobile phase or the sample matrix, or due to the gas chromatographic temperature program, a baseline of at least 5 times the width at half-height is permitted.