This letter presents a microelectrode cell dedicated to direct assessment of the solid-liquid interface noise without recourse to a reference electrode. In the present design, two identical TiN electrodes of various sizes are used for differential measurements in KCl-based electrolytes. Measured noise of the TiN vertical bar electrolyte system is found to be of thermal nature. Scaling inversely with electrode area, the noise is concluded to mainly arise from the solid-liquid interface. This noise is comparable to or larger than that of the state-of-the-art MOSFETs. Therefore, its influence cannot be overlooked for the design of future ion sensors.