scope:

This part of ISO 11843 is concerned with mathematical methodologies for estimating the minimum detectable value in case that the most predominant source of measurement uncertainty is background noise which ubiquitously exists in analytical instruments whether or not a sample is applied to the instrument. The minimum detectable value can directly and mathematically be derived from the stochastic characteristics of the background noise. It specifies basic methods to - extract the stochastic properties of the background noise, - use the stochastic properties to estimate the standard deviation (SD) or coefficient of variation (CV) of the response variable, and - calculate the minimum detectable value based on the SD or CV obtained above. The methods described in this part of ISO 11843 are useful for checking the detection of a certain substance by various types of measurement equipment in which the background noise of the instrumental output predominates over the other sources of measurement uncertainty. Feasible choices are visible and ultraviolet absorption spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, luminescence spectrometry, liquid chromatography and gas chromatography. The definition and applicability of the minimum detectable value are described in ISO 11843-1 and ISO 11843-2 and those of the precision profile are in ISO 11843-5. The precision profile expresses how the precision changes depending on the net state variable. Part 7 of ISO 11843 specifies the practical use of the fundamental concepts in ISO 11843 in case of the background noise predominance in instrumental analysis. The minimum detectable value, xd, is generally expressed in the unit of the net state variable. If the calibration function is linear, the SD or CV of the response variable estimated in this part of ISO 11843 can linearly be transformed to the SD or CV of the net state variable, which in turn can be used for the estimation of the minimum detectable value, xd. If the calibration function is non-linear, the precision profile of the response variable in this part of ISO 11843 needs to be transformed to the precision profile of the net state variable as shown in ISO 11843-5. In this situation, the contents of ISO 11843-5 can be used for this purpose without the slightest modification.