= Blank value
A <blank value> is the measured quantity value obtained by applying an appropriate conversion function to a <blank indication>. The <analytical blank> is the material, the <blank indication> is the observed response, and the <blank value> expresses that response on the scale used for the measured quantity. Keeping those stages distinct prevents treating detector units as an <analyte> <concentration> without <instrument calibration>.<Compendium of Terminology in Analytical Chemistry by IUPAC>[Chapter1, printed page4, §§1.13–1.15]{ref}
An invented additive model makes the conversion explicit. Let a response be $Y=4(c_A+c_B)+2$, where concentrations are in micromolar, $c_A$ is the sample contribution and $c_B$ the process background. The 2-unit offset is electronic. If $c_B=1$, the blank indication is 6 units and the function $f(Y)=(Y-2)/4$ gives a <blank value> of 1 micromolar. A sample with $c_A=2$ gives 14 units and a converted value of 3 micromolar.
Under this stated model, subtracting the converted <blank value> gives $3-1=2$micromolar. Equivalently, $(14-6)/4=2$. Applying the full offset-containing function to the already-subtracted response instead gives $f(8)=1.5$, subtracting the offset again. Thus conversion and <blank correction> must be placed consistently within the measurement model. A nonlinear conversion or nonadditive background can require different reasoning; the numerical example does not select a universal correction rule.
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