A graph illustrating the calibration procedure.

(A) Behavior of luminescence lifetime during calibration (blue). The total volume of liquid injected is shown as red dots, orange crosses indicate injection points on the lifetime graph. After injections, the bottle was flushed with 75 ppm oxygen reference gas and equilibrated with the ambient pressure (green rectangle). (B) The luminescence lifetime of the dye as a function of the effective injected reference liquid volume. Red line is the initial approximation and blue line is the final approximation that compensates for the unintentional inflow of oxygen. (C) Effective amount of oxygen in the gas phase in the units of the injected volume of the reference solution. Red line shows the initial approximation and blue the final one. (D) Calibration curves for the luminescence lifetime as a function of the partial pressure of oxygen with 75 ppm oxygen reference gas in N2 used a calibration point. Red is the initial approximation and blue the final one.