Division 4.1.2 Determination of the resolution (see Appendix A)F1
United Kingdom
Calculate the resolution, R, of two neighbouring peaks I and II, using the formula:
R = 2 × (( d dr(II) – d r(I) )/(ω (I) + ω (II) )) or R = 2 × (( t r(II) – t r(I) )/(ω (I) + ω (II) )) (USP) (United States Pharmacopeia),
or
R = 1,18 × (( t r(II) – t r(I) )/(ω 0,5(I) + ω 0,5(II) )) (EP, BP, JP, DAB), (JP (Japanese Pharmacopeia), EP (Pharmacopée Européenne), BP (British Pharmacopeia))
where:
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d r(I) is the retention distance of peak I;
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d r(II) is the retention distance of peak II;
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t r(I) is the retention time of peak I;
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t r(II) is the retention time of peak II;
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ω (I) is the width of the base of peak I;
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ω (II) is the width of the base of peak II;
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ω 0,5 is the peak width of the specified compound, at mid-height of the peak;
If ω (I) ≈ ω (II) , calculate R using the following formulas:
R = ( d r(II) – d r(I) )/ω = ( d r(II) – d r(I) )/4σ
where:
σ is the standard deviation (see Appendix A, Figure 1).
If the distance dr between the two peaks d r(II) - d r(I) is equal to 4σ, the resolution factor R = 1.
If two peaks are not separated completely, the tangents to the inflection points of the two peaks intersect at point C. In order to completely separate the two peaks, the distance between the two peaks must be equal to:
d r(II) - d r(I) = 6 σ from where R = 1,5 (see Appendix A, Figure 3).