Linearity, Working Range

The linearity and working range of a method are determined by examining the samples with different analyte concentrations and determining the concentration range for which acceptable calibration linearity and measurement uncertainty can be achieved. Linearity can be assessed by visual inspection of a plot of measured responses against standard concentrations, or by statistical measures. The calibration response does not have to be perfectly linear fro a method to be effective, providing an appropriate calibration function is established. The working range is defined as that region where the results will have acceptable uncertainty. The working range can be greater than the linear range. The lower end of the working range is defined by the limit of quantitation and the upper end by the point where there is insufficient change of responses per unit change of concentration, as shown in the picture:

(Insert Linearity picture here)