Calibration functions for CE can be calculated by using peak heights or areas. The relationship between peak heights and concentrations is non-linear, but can well be approximated by a parabolic function. The precision of peak heights is often better than of areas. However, the sensitivity of the calibration function decreases at higher concentrations. Thus calibration functions calculated by using areas lead to a better precision of the analytical result, which is estimated by the slope-normalized standard deviation.