CH 11 · notes
How it works
Relative response factor (RRF) compares how strongly an impurity and the API respond per unit concentration. The default is RRF = (A_imp ÷ C_imp) ÷ (A_api ÷ C_api). Slope mode uses RRF = slope_imp ÷ slope_api. The correction factor shown with those modes is CF = 1 ÷ RRF. Some pharmacopoeias define CF that way; some labs invert the RRF definition itself—use the convention control to match your method.
Impurity mode estimates impurity percent from peak areas and an entered RRF. The concentration form is impurity % = (A_imp ÷ A_api) × (1 ÷ RRF) × (C_api,std ÷ C_sample) × 100. Area-% mode drops the concentration ratio and still uses CF = 1 ÷ RRF.
Worked example
Invented peak areas 12000 (impurity at concentration 0.05) and 100000 (API at concentration 1) give RRF 2.400 and CF 0.4167. Load example fills the same numbers.
Related tools
For single-step dilutions see the C1V1 calculator. Solution preparation is on the Molarity calculator.
FAQ
What is relative response factor?
Relative response factor (RRF) compares the detector response of an impurity to that of the API on a per-concentration basis. The default here is RRF = (A_imp ÷ C_imp) ÷ (A_api ÷ C_api).
How is the correction factor related to RRF?
This page shows CF = 1 ÷ RRF under the selected convention. Some pharmacopoeias use that CF definition. Some laboratories invert the RRF definition itself; choose Inverted when your method writes RRF as API response over impurity response.
When should I use area-% instead of the concentration form?
Use area-% when impurity percent is reported from peak areas with CF = 1 ÷ RRF and no separate standard-to-sample concentration ratio. Use the concentration form when C_api,std and C_sample are part of the calculation.
Does the page upload my peak areas?
No. The calculation stays in the browser. The panel notice is the data statement for this page.