The demand to measure electric interfacial potentials in order to characterize the solid solution interface lead to the development of various apparatus. Those differ from each other in the used electrokinetic phenomena, which are electrophoresis, streaming potential, electroosmosis and migration potential. Electrokinetic measurements on quartz on the basis of streaming potentials have been done with the Electrokinetic Analyzer EKA (A. Paar KG, Graz, Austria). The determined zeta potentials are very variable, non reproducible and differ partially strong from results in the literature.Thus the main variables have been found out in a systematic way. Investigations on the influence of different sample preparation and varying physical measurement conditions on the zeta potential are an integral part of this dissertation. Systematic errors of the apparatus have been detected. For example the with a piezosensitive sensor measured pressure has to be corrected. A further source of error are the used filter membranes, which have a pH depending zeta potential themselves. Thus they influence the measured zeta potential of the sample negatively.