Bioequivalence and Bioavailability Forum

Range for calibration is given by the maximum concentrations you expect (upper limit) and the reasonably achievable LLOQ, determined by the LLOD as well as the clinical need to determine such low concentrations. So it depends on your study design (dose, population etc.) and the goal you want to achieve (preclinical, pilot, screening, or pivotal study).

The larger the range you cover, the more likely you will NOT find your data set to be homoscedastic (i.e. equal variance over the concentration range), which is a necessary prerequisite for simple linear regression to be used. Normally you will find a rather constant CV% over a large part of your calibration range. Here you use weighted linear regression. This will massively improve accuracy of your calculated concentrations at the lower end of your calibration curve.

Non-linear methods are not regularly necessary for typical instrumental analytics. These come more into play with stuff like ELISA, radio-receptor assays and stuff like that.

Hope that help.