Disregard limit in EP

[Nordlin]

Hi

I'm now analyzing chromatographic profile of the Peppermint oil using EP method, and I have some problems with understanding how to use disregard limit.

In method is told: "The area of the principal peak in the chromatogram obtained with reference solution (b) (0.05%)"

Solution (b) contain only 1 standart substance A.
On chromatogram I see only 2 peak, Standart substance A and 1 impurity, with peak area 1.5 and 1.6.

What I need to do next, and how to use this disregard limit?

[dlbenach]

You need to calculate the percent area of each peak found in your Test Soln. To do this, you divide the area of each peak by the total area of all the peaks in the chromatogram. The total area is the sum of the areas of all the peaks. When adding up the areas of all the peaks to calculate the total area, you can "disregard" any peak areas that are below the peak area of the major peak in Ref soln B.

[Nordlin]

Thank you for info.

But for what is given that 0.05%?

[dlbenach]

The isopulegol in Ref B is present at 0.01 uL/mL. Your test solution concentration is 20 uL/mL. 0.05% of 20 is 0.01. It is saying that you do not have to worry about any peaks less than 0.05% the concentration of your major peak.

[Nordlin]

Thank you!