Calibration standards are used to establish the relationship between the measured response and the concentration of an analyte. For this, a set of standards with known analyte concentration are used. The number of standards used, and the concentration range they cover, depends on what the calibration is to be used for. For quantification, a 7-point calibration is common, spread out evenly over the concentration range covered and always covering the expected concentration of the samples that will be measured.