Unique oxygen analyzer combining a dual emission probe and a low-cost solid-state ratiometric fluorometer

A new oxygen analyzer combining a polymer-encapsulated dual-emission probe and a diode-based ratiometric fluorometer is described. The ratiometric flu orometer was configured to measure the relative fluorescence and phosphores cence intensity of the short-lived singlet and long-lived oxygen-quenchable triplet of [(dppe)Pt{S2C2(CH2CH2-N-2-pyridinium)}](BPh4), where dppe is 1, 2-bis(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 photodi odes at 570 and 680 nm, respectively. Oxygen can be accurately measured wit hout interference from nonanalyte-induced intensity changes by monitoring t he relative output of the two photodiodes. The output of the device was lin ear with oxygen concentration. The PO2(1/2) from the ratio-adapted Stern-Vo lmer plot was 9.6% oxygen (approximate to 73 torr), offering a dynamic rang e of 0-90% O-2. The device is stable and the oxygen measurements reproducib le. Intentional photobleaching of approximate to 20% of the sensor dye had little effect upon the reproducibility of the oxygen measurements.