LOD and LOQ Calculator (ICH Q2: 3.3σ/S and 10σ/S)

Calculate detection and quantitation limits from the calibration slope and response SD.

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Calibration slope S response per unit conc.

Standard deviation σ response

σ taken from

Example: slope and residual SD from a low-level calibration curve near the expected limit.

LOD–

LOQ–

LOD = 3.3σ/S · LOQ = 10σ/S

How it works

ICH Q2 describes three ways to set detection and quantitation limits: visual evaluation, signal-to-noise, and the standard deviation of the response with the slope. The calculation approach uses σ from the residual SD of a calibration curve in the range of the limit, the SD of the y-intercepts, or the SD of blank responses.

Use a calibration curve built near the expected limit; a curve spanning the full working range overestimates σ at the bottom end. Whatever approach you use, verify the limits with real injections.