 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.^[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.