Which properties define the sensitivity during the measurement?

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sensitivity

Sensitivity is an indicator for assessing a measuring method and is defined as follows:

definition
The change in the response of a measurement signal divided by the corresponding change in the triggering variable.

The sensitivity of a linear measurement function with as a signal value and as a sample value is given by its slope:

.

The (differential) sensitivity of a non-linear function such as is

,

where,, are constants.

The sensitivity of an analytical method corresponds to the slope of the calibration curve (calibration).

If the calibration curve is not linear, the sensitivity varies depending on the concentration of the measured variable.

If the sensitivity depends on the matrix, calibration using the pure substances is inadequate. In this case the standard addition method can be used to allow an accurate determination of the analyte concentration. The standard addition method can only be used if there is a linear relationship between the measurement signal and the concentration of the analyte. This is necessary because the extrapolation is linear. Despite the disturbance of the matrix, the standard addition method should only be used to correct effects that only lead to changes in sensitivity.

Lead can be determined by the optical emission spectrometry with inductively coupled high frequency plasma (Inductively Coupled Plasma Optical Emission Spectrometry ICP-OES).

example

A two-point calibration for the determination of in water using ICP-OES gives the following values ​​(arbitrary units w.E. for the signal).

Tab. 1
in /Signal in w.E.
12,515,4
23,519,5

The slope of the calibration line is 0.373. This is the sensitivity of the lead determination. If possible, a multi-point calibration should be carried out.