Microsphere-based ion-selective bulk optodes for the determination of clinical electrolytes and the evaluation of closo-dodecacarborane anions as ion exchangers in potentiometric and optical cation-selective chemical sensors

In the attempt to create an ion-sensing strategy that could streamline all available clinical diagnostic assays into one platform, ionophore-based polymeric microspheres were developed that function in complete analogy to traditional hydrophobic bulk optode thin films. Several fabrication methods including solvent casting and heterogeneous polymerization techniques were employed to produce the ion-sensitive particles.; A more convenient method used to prepare monodisperse particles is described based on an automated particle casting technique. This approach produces uniform spheres at a rate of 20,000 particles per second. The casting process is based on a reproducible polymer drop formation and precipitation process, and the particles are formed under very mild, non-reactive conditions. This allows one to conveniently incorporate known amounts of different active components into the polymers. With a RSD of 1.6%, sensing reproducibility from particle-to-particle was excellent. This made it possible to characterize the microspheres using a flow cytometer, which is capable of high-throughput analyses. Separate solution analysis of sodium and potassium-selective microspheres resulted in the generation of functional response curves using peak channel fluorescence intensities. The selectivity observed for both types of particles is sufficient for the clinical determination of Na+ and K+. Furthermore, sodium and potassium-selective microspheres were analyzed in parallel using sodium sample solutions, resulting in the successful determination of sodium ion concentrations and providing important information about the selectivity of the potassium-selective sensors over sodium.; It is quite evident that the lifetime of the miniaturized sensors described in this dissertation will ultimately be dictated by the retention of the sensing components. Several attempts have been made to potentially improve sensor lifetime by designing new polymeric materials that will function without the addition of an external plasticizer. Hexanedioldiacrylate (HDDA) cross-linked dodecyl acrylate (DDA) microspheres ranging from approximately 1–10 μm in diameter were prepared via photoinitiated dispersion polymerization and incorporated with ETH 5294, producing independent self-referencing optodes capable of measuring the activities of H+ and NO ₃− in aqueous media. In order to be used with the particle fabricating apparatus described above, a polymer must be readily soluble in common organic solvents therefore another polymer was developed that did not contain cross-linking units. Plasticizer-free methyl methacrylatedecyl methaerylate (MMA-DMA) microspheres were characterized that contained either ETH 5294 only or ETH 5294, a K+-selective ionophore (BME-44), and anionic sites (NaTFPB). Both sensor formulations functioned in analogy to their plasticized PVC counterparts described above.; In addition to eliminating plasticizer leaching, halogenated carba- closo-dodecacarborane monoanions were evaluated in both ISEs and thin-film optodes for their suitability as ion-exchangers in cation-selective chemical sensors. (Abstract shortened by UMI.)...