Abstract
A new oxygen analyzer combining a polymer-encapsulated dualemission probe and a diode-based ratiometric fluorometer is described. The ratiometric fluorometer was configured to measure the relative fluorescence and phosphorescence intensity of the short-lived singlet and long-lived oxygen-quenchable triplet of [(dppe)Pt{S<sub>2</sub>C<sub>2</sub>(CH<sub>2</sub>CH<sub>2</sub>-N-2-pyridinium)}](BPh<sub>4</sub>), where dppe is 1,2-<i>bis</i> (diphenylphosphino)ethane. This luminescent dye was immobilized at 0.3% by weight in cellulose acetate/75% triethylcitrate and cast into a 0.5 mm-thick film. The dye molecule was excited with a blue light-emitting diode (LED) and the singlet and triplet emissions monitored by individual photodiodes at 570 and 680 nm, respectively. Oxygen can be accurately measured without interference from nonanalyte-induced intensity changes by monitoring the relative output of the two photodiodes. The output of the device was linear with oxygen concentration. The <i>P</i>O<sub>2</sub>(1/2) from the ratio-adapted Stern-Volmer plot was 9.6% oxygen (≊73 torr), offering a dynamic range of 0-90% O<sub>2</sub>. The device is stable and the oxygen measurements reproducible. Intentional photobleaching of 20% of the sensor dye had little effect upon the reproducibility of the oxygen measurements.
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