Kinetics and Transient Times of Fluorescence Optical Sensors (Optodes) for Blood Gas Analysis (O2, CO2, pH)

  • N. Opitz
  • D. W. Lubbers
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 215)


Oxygen measurements with optical sensors (O2 optodes) (Lubbers and Opitz, 1983; Opitz and Lubbers, 1984) are based on fluorescence quenching of certain indicator molecules by molecular oxygen in a diffusion-controlled collisional process (Vaughan and Weber, 1970; Knopp and Longmuir, 1972). The functional dependence follows Stern-Volmer’s equation (Stern and Volmer, 1919) : S (P O2) = S0/ (1+KηPO2), where K is overall quenching constant, PO2, oxygen partial pressure, and S and So, relative fluorescence intensity in the presence and absence of oxygen, respectively. Since fluorescence optical sensors incorporate membrane-protected indicator layers, an exponential time course of the PO2 within these layers can be assumed (Jost, 1960), if a rectangular PO2 step, ΔP O2 = PO2″ − PO2′, is induced in front of the sensor membrane. Insertion of this time course into the hyperbolic calibration curve brings about asymmetrical kinetics of reversible reactions with different transient times, e.g. to 90% of final value (t90):
$$\begin{matrix}t_{90,02}^{\downarrow }={{k}^{-1}}\cdot \log \left( 10-\left( 9\cdot k\cdot \Delta P{{O}_{2}} \right)/\left( 1+k\cdot P{{O}_{2}}\prime\prime \right) \right) \\t_{90,02}^{\uparrow }={{k}^{-1}}\cdot \log \left( 10+\left( 9\cdot k\cdot \Delta P{{O}_{2}} \right)/\left( 1+k\cdot P{{O}_{2}}\prime\right) \right) \\\end{matrix}$$
where k−1 ~ D02/12, D02, oxygen diffusion coefficient and, 1, thickness of the sensor membrane.


Step Height Relative Fluorescence Intensity Transient Time Sensor Membrane Oxygen Diffusion Coefficient 


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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • N. Opitz
    • 1
  • D. W. Lubbers
    • 1
  1. 1.Max-Planck-Institut fur SystemphysiologieDortmund 1Germany

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