Oxygen sensing in nonaqueous media using porous glass with covalently bound luminescent Ru(II) complexes

A comparative study of the oxygen-quenching features of novel luminescent Ru(II) complexes, covalently attached to controlled porous glass (CPG), has been performed in methanol, chloroform, toluene, cyclohexane, and n-hexane, The investigated dyes contain 1,10-phenanthroline-4,7-bis(phenylsulfonate) (s2d), 5-acetamide-1,10-phenanthroline (acap), and 5-tetradecanamide-1,10-phenanthroline (tdap) coordinated to the Ru(s2d)(2) moiety. The immobilization procedure involves stable sulfonamide linkages to amino-derivatized CPG-Glycophase, the loading being a function of indicator molecular size (i.e. highest for the [Ru(s2d)(2)(acap)](2-) dye). Steady-state and time-resolved emission analysis have revealed that oxygen quenching is purely dynamic and occurs on the glass bead surface. Using a continuous-flow system and a conventional spectrofluorometer, a detection limit of 6.2 mu M (200 ppb) oxygen in methanol has been achieved and a 2-4-fold one in the other organic solvents tested, with dynamic ranges over two decades. The analytical figures of merit make the fabricated sensing phases suitable for fiber-optic industrial monitors and oxygen transducers for optical biosensing in nonaqueous media.