Grazing emission X-ray fluorescence analysis (GEXRF) is a new approach of X-ray fluorescence analysis to determine light elements by using very small take-off angles for the fluorescence radiation. The technique is in high demand in quantification procedures, since the two known theoretical ways of deduction do not cover all possible cases met in the analyses. They do not match the situations, e.g., where the samples show non-ideal flat surfaces, but have irregular, non-periodic structures. Additionally, a number of fundamental data are often not known accurately enough, or are even unknown. We have tested two empirical methods of quantification, which are already well established in classical X-ray fluorescence analysis: the calibration and the standard additions method. In particular the influence of matrix elements on the determination of the main component has been tested. Finally, for samples with large and flat surfaces (e.g., wafers), the use of the scattered lines for quantification is proposed. Topographical restructurization of the sample surface during a spin coating process seems to be confirmed by the shifts in the critical angle.