Hello! I am working with derivatized samples on GCMS, running external standard solutions (2-200 ug/mL) to build a calibration curve. Each standard and sample also has the same amount of internal standard. I would like to split my calibration curve into two sections (2-20 ug/mL and 20-200 ug/mL) to have two linear regressions for each segment. Thus far non-linear fits are working better, but standard practice from colleagues was manually splitting at the 20 ug concentration with two seperate linear regressions to account for the different response behaviours at low/high concentrations.
Is there a way to do this? I've tried different level names but can't figure out if this is supported. Thank you!