Free Detection Limit Calculator
Calculate the limit of detection (LOD) and limit of quantitation (LOQ) from blank standard deviation and calibration sensitivity.
Limit of Detection (LOD, 3sigma)
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Limit of Detection (LOD, 3sigma) vs Standard Deviation of Blank (sigma)
Limit of Detection and Quantitation
LOD is the lowest analyte concentration that can be reliably detected (S/N ≈ 3). LOQ is the lowest concentration that can be quantified with acceptable precision (S/N ≈ 10).
Formulas (ICH Method)
LOD = 3.3 × sigma / S (often simplified to 3 × sigma / S)
LOQ = 10 × sigma / S
where sigma is the standard deviation of the blank response and S is the slope of the calibration curve. This is the most common approach in pharmaceutical and environmental analysis.
Example Calculation
Blank standard deviation = 0.005, calibration slope = 2500 signal/M.
- 01LOD = 3 × 0.005 / 2500 = 0.015 / 2500 = 6.0 × 10⁻⁶ M = 6.0 uM
- 02LOQ = 10 × 0.005 / 2500 = 0.05 / 2500 = 2.0 × 10⁻⁵ M = 20 uM
Frequently Asked Questions
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