Due to increased surveillance, continuous monitoring, and rapid diagnostic standards, one must comply with the new standards. Current analytical methods are expensive, require highly qualified staff, and barely keep pace with growing industry demands. That’s especially true for ion-selective electrodes. Even the most expensive of them needs to be calibrated regularly, sometimes after only a few hours of use, and they frequently get clogged, sometimes even irreversibly.
We are currently developing a technological platform for the low-cost mass production of highly selective/sensitive ion-selective optical fibers that meet the needs of industry and comply with current standards. The main advantages of these ion optodes are that they are precalibrated, unaffected by electromagnetic interference or transmission loss, and can be easily and inexpensively replaced. Light does not penetrate the solution, which means the optical fiber can function in opaque solutions. As with standard electrodes, the concentration range depends on pH level (see PDF document).
How does an ion-selective optical fiber work?
An ion-selective optical fiber is an optical fiber with a coating that is sensitive to a specific ion, making it possible to determine concentrations of that ion in a given solution. This polymer fiber (optode) is made by replacing the standard cladding with a membrane composed of a polymer matrix, an ionophore specific to the target ion, and a dye indicator. The color (absorption) of the dye indicator depends on the presence of the specific ion bonded to the ionophore in the membrane. It is the variation of the spectrum of the light signal transmitted through the fiber that allows us to determine the amount of ions present in the membrane. When the ionic equilibrium is reached, a simple calculation based on the dye concentration in the membrane provides the concentration of ions in the solution into which the fiber has been placed.
We have developed ion-selective optical fibers for positive ions like calcium and sodium. It could be possible ion-selective fibers for any ion for which there exists a specific ionophore. We are presently working on a pH sensor.