Method Validation Parameters
Definition
The numbers a forensic method must hit before it is considered fit for routine use: linearity R² > 0.999 over the working range, LOD and LOQ at signal-to-noise of 3 and 10, intra-day and inter-day precision RSD below 2 to 5 percent, accuracy or recovery of 90 to 110 percent, and robustness against small mobile-phase or temperature changes. The Indian Pharmacopoeia and the FSSAI manuals codify these acceptance criteria.
- Linearity target
- R² > 0.999 over working range
- LOD/LOQ basis
- Signal-to-noise of 3 and 10
- Precision target
- RSD below 2 to 5 percent
- Accuracy target
- 90 to 110 percent recovery
- Reference codes
- Indian Pharmacopoeia, FSSAI manuals
Common questions
Why does a lab need to validate a method before using it for casework, rather than just running the instrument?+
Validation demonstrates the method reliably measures what it claims to measure within stated error bounds, which is what makes a quantitative result defensible in court. An unvalidated method can produce numbers that look precise but carry undocumented, potentially large systematic error.
What is the practical difference between LOD and LOQ in a validated method?+
LOD, at signal-to-noise of 3, is the lowest amount that can be reliably distinguished from background noise and detected, while LOQ, at signal-to-noise of 10, is the lowest amount that can be quantified with acceptable precision and accuracy. A substance can be detected below the LOQ but not reliably quantified there.
Related terms
- Densitometric Scanning
- The HPTLC quantitation step. After the developed plate dries, a Camag TLC Scanner 4 sweeps a narrow slit of UV or visible...
- Diode Array Detector (DAD)
- A UV-Vis detector that records the full 190 to 800 nm absorbance spectrum of every peak as it elutes, instead of a...
- Isocratic vs Gradient Elution
- Isocratic means the mobile-phase composition stays constant through the run; simple, reproducible, but limited resolving power for wide-polarity mixtures. Gradient means the...
- Reverse-Phase Chromatography
- Liquid chromatography with a non-polar stationary phase (most commonly octadecyl-bonded silica, called C18) and a polar mobile phase (water mixed with methanol...
- Sub-2 µM Particle Column
- A UHPLC column packed with 1.6 to 1.8 µm silica particles instead of the conventional 5 µm. Smaller particles give sharper peaks...