A sensitive probe for oxygen sensing in gas mixtures, based on room-temperature phosphorescence quenching

The dye Erythrosine B (which gives room-temperature phosphorescence, RTP) has been covalently bound to a silica-based amino-functionalized exchanger. The resulting material turned out to be extremely useful as a luminescent probe for oxygen. The photochemical properties and the analytical performance of the RTP probe have been studied by use of a gas flow-injection analysis system, which incorporates a convenient exponential dilution chamber for gas sample introduction. The possible origin of the non-linear Stern-Volmer quenching response observed is thoroughly discussed in terms of the quenching and lifetimes. The proposed sensing material is particularly suitable for measuring oxygen in gas mixtures at extremely low concentrations. The detection limit attained was 0.00006% (0.6 ppm) of oxygen in dry argon (making the system one of the more sensitive opto sensors for oxygen published so far). A typical precision of +/- 0.2%, at the 0.025% oxygen level, was achieved. Response times were less than 2 s for full signal change and no hysteresis effects were noticed. A possible mechanism for the observed oxygen RTP quenching in the new sensing material is proposed.