SBIR Phase II: Nanofluidic Reference Electrode with an Invariant Liquid Junction Potential

This Small Business Innovative Research (SBIR) Phase II is for the development of nanofluidic-flowing liquid junction (NFLJ) reference electrodes using nanochannel glass arrays developed by the Naval Research Laboratory. While consuming electrolyte at less than 2 ml/yr, the NFLJ reference electrodes will allow a flow at velocities of over 0.1 cm/sec to impede back diffusion of sample solution into the electrode. A variety of challenging test sample solutions, potentiometric measurements made with NFLJ references varied < 0.5 mV with response times of less than 60 seconds while measurements made with conventional reference electrodes varied up to 20 mV with response times of over one hour have already been completed. The NFLJ reference electrode's exceedingly small electrolyte consumption makes possible handheld NFLJ pH sensors with significantly higher precision and longer operational life. The high impedance of NFLJ reference electrodes, when using modern commercial pH electrodes, has no measurable effect on the precision, response time, or span of the pH measurement. The nanochannel glass nanofluidic-flowing liquid junction (NFLJ) adds a new dimension to the design and construction of reference electrodes. The unique ability of the NFLJ design to separate flow volume and flow velocity will provide scientists with a tool for investigating reference electrode behavior as a function of flow, velocity, and resistance. It should help to develop a more fundamental understanding of mass transfer effect on liquid junction potentials. Initial results indicate that velocity is the critical parameter in stabilizing the potential.