Summary form only given. RF-Glow Discharge Optical Emission Spectrometry is a well established technique for direct compositional depth profiling (CDP) analysis of solid, conducting and non-conducting samples. The technique is based on sputtering surface atoms and their subsequent excitation in the discharge. The separation of sputtering and excitation makes the technique very little prone to matrix effects. The quantification procedure is based on the observation that emission yields depend strongly on the source impedance, which varies with the carrier gas density and the secondary electron emission yield of successively sputtered layers. Despite the apparent success, it lacks theoretical back-up and its extension to non-conductive materials is difficult.