Using the Calibration Function:
The main aim of deriving a calibration equation is obviously to determine the concentration of analyte in various samples (our ‘unknowns’) from the corresponding mesaured value of the instrument response. Mathematically, this requires an interpolation of the measurement (signal or response) through the calibration function. This obviously involves substituting the measured response (y0) into the regression line and solving for the concentration (x0).
The problem now is that we have uncertainty in both the measured value y0 and the parameters of our calibration function (i.e. the slope and intercept of the regression line.) As with any other experimental measurement, the uncertainty in the measured value can be reduced by performing replicate determinations; we therefore additionally need to take into account the number of such replicates in determining the uncertainty in the interpolated sample concentration.