Technology

TecSense / Technology

Master your Oxygen!
TecSense uses opto-chemical sensor technology to determine gaseous and dissolved Oxygen concentrations in a wide concentration range – from 4ppb (parts per billion) to 40%). Opto-chemical sensors are extremely accurate, cover a wide range of applications and are easy to maintain.

The optochemical oxygen measurment system offers outstanding features:

  • measuring range from 4 ppb up to saturation
  • minimal response time t90 = 250 ms
  • highest accuracy +-±0,003 mg/l
  • maximal reproducibility of 99,99%
  • self diagnosis
  • self calibration applying coded sensor spot technology
  • temperature range from – 20 °C to +135°C
  • miniaturised, integrated measurement device
  • no cross sensitivity to CO2, SO2, ionic strength
  • CIP cleaning, SIP sterilization of the sensor
  • no constraints regarding installed location, material flow or pressure

The measurement principle is described here:

  • Detection of a sensitive spots luminescence after irradiation at a specific wave length
  • Luminescence quenching:
  • Oxygen acts as “Quencher”
  • Irradiation
  • Emission of fluorescence light (Stoke´s Shift)
  • Collision with quencher (e.g. Oxygen)
  • Oxygen absorbs the energie of the activated  dey molecule
  • Reduction of the emitted lights intensity
  • Reduction of life time of the activated luminophor
  • Phase shift between irradiation signal and emitted signal
How it works

The principle of “opto-chemical” or “optical”oxygen detection.

A luminescent (often named fluorescent) dye molecule (indicator substance) is irradiated with light of a characteristic wavelength (e.g., 520 nm), which then emits light at a longer wavelength. This shift is called “Stoke’s” shift, the whole phenomenon fluorescence or luminescence.

This luminescence light “lights up”, which means that it is still lit for a while after switching off the excitation light. This time is referred to as the “lifetime of the luminescence process”; it is between nano seconds and a few seconds, depending on the used dye.

The properties of the emitted light are influenced by the concentration of analyte (the substance to be detected) and the environment of the luminescence dye. When choosing the right luminescence dye, the luminescence lifetime can be determined by measuring the intensity of the luminescence light as a function of time. The concentration of oxygen O2 can be determined therefrom. The measurement of the lifetime is much more reliable than measuring the intensity and is therefore more suitable for stable measurements.

opto-chemical oxygen determination

Excitation of luminescence by energy absorption at a specific wavelength.
Emission is shifted to longer wavelength (Stoke’s shift)

Excitation (left side of the maximum) and decay (right side of the maximum) of the luminescence indicating the luminescence life time.

Principle setup of an opto-chemical device: Luminescence excitation and detection using a LED respectively a photodiode. The oxygen sensitive dye is embedded into a polymer layer (sensitive layer).

Luminescence life time as a function of oxygen concentration. The curve is fitted with a 3 component “False light” model.

Relevant Literature
  1.  O. Stern and M. Volmer, Über die Abklingungszeit der Fluoreszenz,
    Physik. Zeitschr., pp. 183-188, (1919).
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  3. Draxler S., Lippitsch M.E., Klimant I., Kraus H., Wolfbeis O.S. Effects of polymer matrices on the time-resolved luminescence of a ruthenium complex quenched by oxygen. Journal of Physical Chemistry. 1995;99:3162–3167.
  4. Demas J.N., DeGraff B.A., Coleman P.B. Oxygen sensors based on luminescence quenching. Analytical Chemistry. 1999;71:793A–800A.
  5. Bizzarri A. et al., “Opto-chemical sensor for oxygen measurements in sealed packages,” Proc. 4th Int. Conf. Optoelectronics (Erfurt,Germany), pp. 193-198, 2000.
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  7. Lakowicz J.R., Principles of Fluorescence Spectroscopy, Springer, Berlin, 3rd edn, 2006.
  8. Vos J.G., Kelly J.M. Ruthenium polypyridyl chemistry; from basic research to applications and back again. Dalton Transactions. 2006:4869–4883.
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  13. Mark J.E. 2nd edition. Oxford University Press; USA: 2009. Polymer Data Handbook.
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  16.  McDonagh, C., Burke C.S., MacCraith B.D., Optical Chemical Sensors, Chem. Rev., vol. 108, pp. 400-422, 2008.
  17. Knall A., Tscherner M., Noormofidi N., Pein A., Saf R., Mereiter K., Ribitsch , Stelzer F., Slugovc Ch.,Nonradiative deactivation of europium(III) luminescence as a detection scheme for moisture. The Analyst 11/2011; 137(3):563-6.
  18. Goossens G.H., Bizzarri A., Venteclef N., Essers Y., Cleutjens J.P., Konings E., Jocken J., Cajlakovic M., Ribitsch V., Clément K., Blaak E.E., Increased adipose tissue oxygen tension in obese compared with lean men is accompanied by insulin resistance, impaired adipose tissue capillarization, and inflammation. Circulation 06/2011; 124(1):67-76.
  19. Cajlakovic M., Bizzarri A., Goossens G.H., Knez I., Suppan M., Ovina I., Ribitsch V., Optochemical Sensor Systems for In-Vivo Continuous Monitoring of Blood Gases in Adipose Tissue and in Vital Organs, 01/2012; ISBN: 978-953-307-792.
  20. Lamprecht B., Tschepp A., Cajlakovic M., Sagmeister M., Ribitsch V., Köstler St., A luminescence lifetime-based capillary oxygen sensor utilizing monolithically integrated organic photodiodes. Analyst, 2013, 138: 5875-5.