| 1.116 | limit of detection, (LOD) | ||
| detection limit, (DL) | |||
| True quantity value for a quantity of a component present in a material for which the probability of falsely claiming the absence of the component is β, given a probability α of falsely claiming its presence based on an established criterion for detection. | |||
| Note 1: | The limit of detection is usually considered to be a performance characteristic of a measurement procedure performed in a particular laboratory. | ||
| Note 2: | The quantity is usually a mass fraction or a concentration but can also be for example, a mass or amount of substance. | ||
| Note 3: | The established criterion for detection can be, for example, a critical value which leads to a declaration that the component is present. | ||
| Note 4: | IUPAC recommends default values for α and β equal to 0.05. This corresponds to requiring a level of confidence (see coverage probability Note 2) of 95 % for a statistical test for non-zero true value of the quantity of the component, and to a statistical power of 95 % for that test applied to a material containing the component at the limit of detection. | ||
| Note 5: | The limit of detection is not a criterion for detection but indicates the true value of a quantity of the component in a material that can be detected reliably, given a separate criterion (for example critical value) for declaring the component present. | ||
| Note 6: | If the limit of detection is estimated as a multiple of the standard deviation of measured quantity values of a blank material (or one spiked with a small aliquot of the component) measured under repeatability conditions of measurement, it is important to document the multiplication factor applied so that different values stated for limits of detection can be compared. | ||
| Note 7: | The letter symbols LOD and DL should not replace the quantity symbol but may be given as subscript to the appropriate symbol for the quantity, e.g., wLOD, mDL. | ||
| Note 8: | In ISO 3534-2, ‘minimum detectable value of the net state variable’ is defined as “true value of the net state variable in the actual state that will lead, with probability, 1 − error probability, to the conclusion that the system is not in the basic state”.26 | ||
| Note 9: | According to the definition given here and in ISO 11843, LOD is a (unobservable) true value. This differs from the definition in VIM 4.18 where the concept ‘detection limit’ refers to a measured quantity value.1 | ||
| Note 10: | In some European legislations ‘detection capability’ (denoted as CCβ) is defined as “the smallest content of the substance that may be detected, identified and/or quantified in a sample with an error probability of β”.37 | ||
| Note 11: | The ISO 11843 series “Capability of detection” covers a wide field related to “the detection of a difference between an actual state of a system and its basic state”, which additionally includes cases in which the “basic state” does not correspond to absence (zero concentration) of a component.38 | ||
| Note 12: | The use of the term “sensitivity” for limit of detection is erroneous as it refers to the slope of the calibration curve. | ||
| Note 13: | The US Environmental Protection Agency defines ‘method detection limit’ (MDL) as “the minimum measured concentration of a substance that can be reported with 99 % confidence that the measured concentration is distinguishable from method blank results”.50 | ||
| See also: ref. 39, 51 and 52. | |||
| 1.116 | limit of detection, (LOD) | ||
| detection limit, (DL) | |||
| True quantity value for a quantity of a component present in a material for which the probability of falsely claiming the absence of the component is β, given a probability α of falsely claiming its presence based on an established criterion for detection. | |||
| Note 1: | The limit of detection is usually considered to be a performance characteristic of a measurement procedure performed in a particular laboratory. | ||
| Note 2: | The quantity is usually a mass fraction or a concentration but can also be for example, a mass or amount of substance. | ||
| Note 3: | The established criterion for detection can be, for example, a critical value which leads to a declaration that the component is present. | ||
| Note 4: | IUPAC recommends default values for α and β equal to 0.05. This corresponds to requiring a level of confidence (see coverage probability Note 2) of 95 % for a statistical test for non-zero true value of the quantity of the component, and to a statistical power of 95 % for that test applied to a material containing the component at the limit of detection. | ||
| Note 5: | The limit of detection is not a criterion for detection but indicates the true value of a quantity of the component in a material that can be detected reliably, given a separate criterion (for example critical value) for declaring the component present. | ||
| Note 6: | If the limit of detection is estimated as a multiple of the standard deviation of measured quantity values of a blank material (or one spiked with a small aliquot of the component) measured under repeatability conditions of measurement, it is important to document the multiplication factor applied so that different values stated for limits of detection can be compared. | ||
| Note 7: | The letter symbols LOD and DL should not replace the quantity symbol but may be given as subscript to the appropriate symbol for the quantity, e.g., wLOD, mDL. | ||
| Note 8: | In ISO 3534-2, ‘minimum detectable value of the net state variable’ is defined as “true value of the net state variable in the actual state that will lead, with probability, 1 − error probability, to the conclusion that the system is not in the basic state”.26 | ||
| Note 9: | According to the definition given here and in ISO 11843, LOD is a (unobservable) true value. This differs from the definition in VIM 4.18 where the concept ‘detection limit’ refers to a measured quantity value.1 | ||
| Note 10: | In some European legislations ‘detection capability’ (denoted as CCβ) is defined as “the smallest content of the substance that may be detected, identified and/or quantified in a sample with an error probability of β”.37 | ||
| Note 11: | The ISO 11843 series “Capability of detection” covers a wide field related to “the detection of a difference between an actual state of a system and its basic state”, which additionally includes cases in which the “basic state” does not correspond to absence (zero concentration) of a component.38 | ||
| Note 12: | The use of the term “sensitivity” for limit of detection is erroneous as it refers to the slope of the calibration curve. | ||
| Note 13: | The US Environmental Protection Agency defines ‘method detection limit’ (MDL) as “the minimum measured concentration of a substance that can be reported with 99 % confidence that the measured concentration is distinguishable from method blank results”.50 | ||
| See also: ref. 39, 51 and 52. | |||