PIXE investigations in Heidelberg utilize very different target types for which analogous standards are very rarely available. Standardless quantitative measurements are therefore the preferred method. This asks for precise beam monitoring and accurate calibration of the setup for the conversion from X-ray counts to concentrations. It will be shown that our beam monitor enables us to measure beam currents down to 1 pA with a precision of ≈ 0.5%. The computer code GUPIX which we use to quantify our results offers the possibility to use a calibration function H( E) rather than one constant only. H( E) has been measured, leading to an overall accuracy for quantification of 5% even for trace elements.