8E Figures of merit for analytical methods
Analytical procedures are characterized by a number of figures of merit such as:
- accuracy, precision, sensitivity, detection limit, and dynamic range.
8E-1 Sensitivity and Detection Limit
The definition of sensitivity most often used is the calibration sensitivity, or the change in
the response signal per unit change in analyte concentration.
The calibration sensitivity is thus the slope of the calibration curve. The calibration sensitivity
does not indicate what concentration differences can be detected. Noise in the response
signals must be taken into account in order to be quantitative about what differences can be
detected. For this reason, the term analytical sensitivity is sometimes used.
Figure 8-14 Calibration curve of response R versus concentration c. The slope of the calibration curve is
called the calibration sensitivity m. The detection limit, DL, designates the lowest concentration that can be
measured at a specified confidence level
The analytical sensitivity is the ratio of the
calibration curve slope to the standard
deviation of the analytical signal at a given
analyte concentration. The analytical
sensitivity is usually a strong function of
concentration.
The detection limit, DL, is the smallest
concentration that can be reported with a
certain level of confidence.