Selectivity
Definition
The ability of a method to measure the target analyte specifically, even when other substances that might plausibly appear in a real sample are present. Tested by spiking samples with known interferents and confirming the target signal is not distorted.
- Domain
- Analytical method validation
- Definition attribute
- Ability to measure the target analyte specifically amid interferents
- Test method
- Spiking samples with known interferents
Common questions
How is selectivity different from sensitivity in method validation?+
Sensitivity is about how small a concentration the method can detect, while selectivity is about whether the signal it detects is genuinely from the target analyte and not distorted by something else present in the sample.
What does a selectivity failure look like in practice?+
A common sign is that the target signal shifts, broadens or gains unexpected shoulders when a known interferent is spiked in, indicating the method cannot cleanly separate the analyte's response from that of the interfering substance.
Related terms
- Limit of Detection (LOD)
- The lowest concentration of analyte that produces a signal reliably distinguishable from the instrument noise, conventionally three times the standard deviation of...
- Limit of Quantitation (LOQ)
- The lowest concentration at which the assay can produce a quantitative measurement with acceptable precision and accuracy, typically defined as the concentration...
- Repeatability
- The agreement between successive measurements of the same specimen made by the same analyst, on the same instrument, in the same laboratory,...
- Reproducibility
- The closeness of agreement between measurements obtained under changed conditions: different analysts, different instruments, different laboratories, or different times. A wider measure...
- Robustness
- The capacity of a method to remain unaffected by small, deliberate variations in its operating parameters, such as slight changes in temperature,...