property of a measuring system, used with a specified measurement procedure, whereby it provides measured quantity values for one or more measurands such that the values of each measurand are independent of other measurands or other quantities in the phenomenon, body, or substance being investigated
EXAMPLE 1 Capability of a measuring system including a mass spectrometer to measure the ion current ratio generated by two specified compounds without disturbance by other specified sources of electric current.
EXAMPLE 2 Capability of a measuring system to measure the power of a signal component at a given frequency without being disturbed by signal components or other signals at other frequencies.
EXAMPLE 3 Capability of a receiver to discriminate between a wanted signal and unwanted signals, often having frequencies slightly different from the frequency of the wanted signal.
EXAMPLE 4 Capability of a measuring system for ionizing radiation to respond to a given radiation to be measured in the presence of concomitant radiation.
EXAMPLE 5 Capability of a measuring system to measure the amount-of-substance concentration of creatininium in blood plasma by a Jaffé procedure without being influenced by the glucose, urate, ketone, and protein concentrations.
EXAMPLE 6 Capability of a mass spectrometer to measure the amount-of-substance abundance of the 28Si isotope and of the 30Si isotope in silicon from a geological deposit without influence between the two, or from the 29Si isotope.
NOTE 1 In physics, there is often only one measurand; the other quantities are of the same kind as the measurand, and they are input quantities to the measuring system.
NOTE 2 In chemistry, the measured quantities often involve different components in the system undergoing measurement and these quantities are not necessarily of the same kind.
NOTE 3 In chemistry, selectivity of a measuring system is usually obtained for quantities with selected components in concentrations within stated intervals.
NOTE 4 Selectivity as used in physics (see Note 1) is a concept close to specificity as it is sometimes used in chemistry.
ANNOTATION (informative) [2 December 2014] Here "quantity values" can be replaced by "values" without ambiguity: "property of a measuring system, used with a specified measurement procedure, whereby it provides measured values for one or more measurands such that the values of each measurand are independent of other measurands or other quantities in the phenomenon, body, or substance being investigated".