# Peak-Valley Ratio calculation

1.0 OBJECTIVE

To lay down the procedure for the Peak-Valley Ratio calculation

2.0 SCOPE

This SOP is applicable for Peak-Valley Ratio calculation

3.0 BACKGROUND

NIL

4.0 RESPONSIBILITY

4.1 QC-Chemist

4.2 QC-Executive

5.0 PROCEDURE

5.1 For measuring separation of two cinematographic peaks there are several methods and the first one is resolution and second one is Peak to valley ratio.

5.2 When to use Peak to valley ratio ?

5.2.1 The peak-to-valley ratio (p/v) may be employed as a system suitability requirement in a test for related substances when baseline separation (Resolution) between 2 peaks is not reached.

Hp = height above the extrapolated baseline of the minor peak,
Hv = height above the extrapolated baseline at the lowest point of the curve separating the minor and major peaks.
Peak to valley ratio is calculated using the following formula
H1=Peak height of the first peak
h2=Peak height of the second peak
Hv=height of the valley between the split peaks

H1≥H2, peak to valley ratio= H2/Hv

H1≤H2, peak to valley ratio= H1/Hv

5.2.3 Comparison between PV ratio and Resolution:

5.2.3.1 The valley to peak ratio is proposed as a measure for the extent of separation of two chromatographic peaks. This quantity is compared with the resolution (R). For two Gaussian curves, a mathematical relation exists between the two quantities.

5.2.3.2 The PV ratio has a larger coefficient of variation than the resolution, thus being the more sensitive quantity for measuring the separation.

5.2.3.3 In cases where there is appreciable tailing, the PV ratio is a better measure for the separation than the resolution. Optimal operation parameters are more easily found by computing the PV ratio than the resolution. When the separation is very poor, it is impossible to determine the resolution whereas the PV ratio can be determined easily.

6.0 ANNEXURES
Nil