Specificity
The ability of a method to measure the analyte accurately in the presence of everything else in the sample.
Unit
Dimensionless
In depth
A perfectly specific method responds to one substance alone. Since few methods achieve this, interferences must be removed by separation, masked by complexing agents, or corrected for mathematically. Coupled techniques gain specificity by combining two independent measurements.
Examples in the real world
GC-MS identifying a compound by both retention time and mass spectrum, making false positives very unlikely.