It might be expected that the variance of each data
point in the calibration curve might be statistically heterogeneous:
in this case, a simple and effective way to counteract the greater
influence of higher concentrations on the regression is to use the
so called Weighted Least Squares Linear Regression (WLSLR)
(Raffo, D’Aloise, Magri, & Leclercq, 2013)