## ASTM E2677 Limit of Detection Web Portal

Definitions and Descriptions

**Limit of Detection (LOD90)**
Expressed in the mass domain, the **LOD90** is the lowest
amount of a particular substance for which there is 90% confidence that
a single measurement will have a true detection probability of at least
90% while the true non-detection probability of a process blank is at
least 90%. The true **LOD90** is difficult to measure
accurately and must be estimated from the data provided. The data
are assumed to be generated from the fully specified ASTM Test Method
under a state of statistical control.

The **LOD90** value is based on a confidence limit of 0.10. Other
confidence limits can be used. Typical values for the confidence limit
are 0.10, 0.05, and 0.01 corresponding to **LOD90**, **LOD95** and
**LOD99**, respectively. For convenience, the documentation will
simply refer to **LOD90**.

**Upper Confidence Limit for LOD90**

At 90% confidence, the possible upper value for the true
**LOD90** given uncertainties in the assumptions of the
predictive model and the limitations in the data provided. This measure of
uncertainty does not include uncertainty in the inputted mass values.

**Critical Value (CV90)**

Expressed in the signal domain, the **CV90** is the lowest instrument
response for which there is 90% confidence that the response signifies the
true detection of a particular analyte. The **CV90** value is somewhat
below the average response value expected for sample replicates prepared at
the **LOD90** mass level, and should relate to the value of the peak
detection (or alarm) threshold that is set in the trace detector assuming
process blank data are realistic.

As with the **LOD**, different confidence limits can be used. The
typical confidence limits of 0.10, 0.05 and 0.01 correspond to
**CV90**, **CV95** and **CV99**, respectively.

**90%-90% Upper Tolerance Limit**

There are two significance levels given for a tolerance limit. The first
level is referred to as the confidence and the second level as the coverage.
The 90%-90% upper tolerance limit is interpreted as the value for
**LOD90** where, at 90% confidence, at least 90% of the possible estimates
of the true **LOD90** lie below. Further information may be found in the
NIST/SEMATECH
Engineering Statistics Handbook.

**Grubbs Outlier Test**

A statistical test used to detect dubious response data (outliers) from a
normally distributed population of data. Further information may be found
in the NIST/SEMATECH
Engineering Statistics Handbook.

**Scalable Vector Graphics (SVG) format**