Reliable, bench-top measurements of charge density in the active layers of thin-film composite and nanocomposite membranes using quartz crystal microbalance technology

► A method was developed to measure charge density in thin-film membranes. ► Charged sites in active layers are probed with cesium ion. ► The cesium mass in the active layer is measured with a quartz crystal microbalance. ► The method is a reliable, user-friendly, bench-top method. ► Thin-film composites and nanocomposites tested had similar ionization behaviors.