How to determine signal to noise ratio? I would like to know the experimental aspects of it.Thanks in advance for the explanation

Signal to noise ratio (S/N) has various uses in HPLC. First, by measuring the S/N one can determine the Limit of Detection (LOD) and Limit of Quantitation (LOQ). To measure the S/N, first measure the height of the peak of interest, using whatever units you want - the Y-axis of the chromatogram, measuring in millimeters with a ruler, whatever. Next, measure the height of a representative sample of your baseline (the noise), somewhere relatively close to your peak, either before or after the peak elutes. The ratio of these two values is your signal to noise ratio (S/N).

The LOD of an assay is the smallest concentration that can be detected reliably. This is usually at a S/N of approximately 3. After performing an injection, if your S/N is less than 3, you cannot confidently detect your peak of interest - it gets lost in the baseline noise.

The LOQ of an assay is the smallest concentration that can be quantitated reliably with a specified level of accuracy and precision. This is usually at a S/N of approximately 10. After performing an injection, if your S/N is less than 10, you cannot confidently quantitate your peaks - there is too much variablility which yields results which are not reproducible.

By increasing the S/N, one can provide an assay with better precision. Your software program which integrates your data can probably calculate S/N, but beware for these software results can be inaccurate. I prefer to calulate S/N by hand. I hope this helps.

The typical way of determining the signal to noise ratio is through the examination of the average heighth of the noise compared to the heighth of the signal(analyte).
Is in regards to Limit of Detection and Quantitation Limit?

Yes, it is with respect to Limit of detection and quantification

A straight forward, easy way to do it is to inject different concentration going the full range where you expected it to be and lower. Measure the highth of a typical baseline noise. Then find the analyte peak that has a peak highth corresponding to 3 times the noise for detection limit and 10 times for the quantitation limit. That is the easiest way I know that is exceptable by the FDA.

There is a formula standard deviation divided by average. is it not the right formula to calculate S/N ratio.

what is height of a typical baseline noise. ?
please explain. thanks in advance.

Dear sir,
i am not clear with this information.
Please send me the diagramatical explanation in HPLC chromatograms with an example.
Thanking you sir

Yours faithfully
J.N.Sateesh
My E-mail ID is : naga_sateesh@yahoo.com