Spatial and spectral imaging of single micrometer sized solvent cast fluorescent plasticized poly(vinyl chloride) sensing particles

Microscale plasticized PVC particles doped with hydrophobic ionophores are prepared by solvent evaporation of aqueous suspensions of sensing cocktails (poly(vinyl chloride), plasticizer, active sensing components, and tetrahy drofuran) and tested as particulate microoptical sensors. The particles con tain either only the chromoionophore ETH 2458 as active reagent or the pota ssium ionophore BME-44, chromoionophore ETH 5294, and lipophilic anionic si tes NaTFPB, The former system functions according to an anion-hydrogen ion coextraction mechanism and shows a Hofmeister anion selectivity pattern, wh ile the latter sensor containing additional ionophores represents the more complex, truly selective optical sensors based on ion-exchange equilibria, Single microspheres are simultaneously characterized spatially and spectral ly by fluorescence microscopy, coupled to a spectrometer equipped with a CC D detector. The results indicate that these microspheres respond in complet e analogy to traditional thin-film-based optodes previously reported in the literature. The introduction of small, spherical ionophore-based sensing p articles that operate on the basis of bulk extraction principles holds the promise of significantly expanding the available chemical palette of micros phere-based analytical assays.