IUPAC Technical Report on Measurement and Interpretation of Electrokinetic Phenomena This report reviews the current state of electrokinetics and provides practical guidelines for performing electrokinetic measurements and interpreting results in terms of well-defined quantities, such as the zeta-potential. The zeta-potential is a property of charged interfaces and should be independent of the measurement technique. However, the excess conductivity of the stagnant layer is an additional parameter. The report discusses basic theories and their application ranges, and provides a thorough description of main electrokinetic methods, emphasizing their applicability and the validity of underlying models. Electrokinetic consistency tests are proposed to assess the validity of zeta-potentials obtained. The recommendations apply mainly to smooth and homogeneous solid particles and plugs in aqueous systems, with some attention given to non-aqueous media and less ideal surfaces. The report defines electrokinetic phenomena as those involving tangential fluid motion adjacent to a charged surface. It describes key concepts such as electrophoresis, electro-osmosis, streaming potential, and streaming current. It also discusses dielectric dispersion, electroacoustics, and other electrokinetic methods. The report addresses the role of surface conductivity, the Dukhin number, and the effects of surface curvature and chemical heterogeneity on electrokinetic behavior. The report outlines the basic problem of evaluating zeta-potentials, emphasizing the importance of accurate measurement and interpretation. It discusses the theoretical basis of electrokinetic phenomena, including the Smoluchowski equation for electro-osmotic slip velocity and the Helmholtz-Smoluchowski equation for electrophoresis. The report also addresses the influence of surface conductivity on electrokinetic behavior, and provides guidelines for converting electrophoretic mobility into zeta-potential. It discusses the validity of different models for various conditions and the importance of considering surface conductivity in electrokinetic measurements. The report also addresses the effects of surface curvature, chemical heterogeneity, and other factors on electrokinetic behavior. Finally, it provides recommendations for experimental techniques and the interpretation of electrokinetic data.IUPAC Technical Report on Measurement and Interpretation of Electrokinetic Phenomena This report reviews the current state of electrokinetics and provides practical guidelines for performing electrokinetic measurements and interpreting results in terms of well-defined quantities, such as the zeta-potential. The zeta-potential is a property of charged interfaces and should be independent of the measurement technique. However, the excess conductivity of the stagnant layer is an additional parameter. The report discusses basic theories and their application ranges, and provides a thorough description of main electrokinetic methods, emphasizing their applicability and the validity of underlying models. Electrokinetic consistency tests are proposed to assess the validity of zeta-potentials obtained. The recommendations apply mainly to smooth and homogeneous solid particles and plugs in aqueous systems, with some attention given to non-aqueous media and less ideal surfaces. The report defines electrokinetic phenomena as those involving tangential fluid motion adjacent to a charged surface. It describes key concepts such as electrophoresis, electro-osmosis, streaming potential, and streaming current. It also discusses dielectric dispersion, electroacoustics, and other electrokinetic methods. The report addresses the role of surface conductivity, the Dukhin number, and the effects of surface curvature and chemical heterogeneity on electrokinetic behavior. The report outlines the basic problem of evaluating zeta-potentials, emphasizing the importance of accurate measurement and interpretation. It discusses the theoretical basis of electrokinetic phenomena, including the Smoluchowski equation for electro-osmotic slip velocity and the Helmholtz-Smoluchowski equation for electrophoresis. The report also addresses the influence of surface conductivity on electrokinetic behavior, and provides guidelines for converting electrophoretic mobility into zeta-potential. It discusses the validity of different models for various conditions and the importance of considering surface conductivity in electrokinetic measurements. The report also addresses the effects of surface curvature, chemical heterogeneity, and other factors on electrokinetic behavior. Finally, it provides recommendations for experimental techniques and the interpretation of electrokinetic data.