Larvae Knowledge Incubator
Larvae Knowledge Incubator
Larvae Knowledge Incubator

FireStingO2- Respirometry with optical oxygen meter

The FirestingO2 is a fiber-optic meter controlled from a PC using an oxygen logger software. There are several types of sensors available (needles, microsensors, sensor spots, respiration vials) to measure temperature and oxygen saturation in gases and liquids.

The FireStingO2 allows for up to four sensors to be attached through input channels (S1-S4) at once for continuous reading of the oxygen content (Figure 1). The FireStingO2 is connected to the PC by a USB-connector and is operated from the Windows-based program Firesting Logger by Pyro Science.

Figure 1: The FireStingO2 optical oxygen meter with four input channels from optic sensors (S1-S4), a temperature input channel (T) and an USB output.
Figure 2: Respirometer setup with one set of 4 vials connected to their respective input channels (1-4) on the fireStingO2 optical oxygen meter.

Respirometer set up

Respiration vials are used for respirometry and metabolic studies of cell cultures, fish eggs and -larvae, small crustaceans, small fish and plants algal sample.

One set consists of 4 respiration vials connected to their respective input channels (1-4) on the FireStingO2 (Figure 2).

Figure 3: Vial for closed respirometry compatible with FireStingO2 respirometer. The vial have a green stripe (arrow). This is an intergrated sensor on the inside of the vial for oxygen measurements.
Figure 4: The adapter ring and the optic fiber cable is fixed to the respirometer vial by screws on the adapter ring.
Figure 5: The measuring principle with FireStingO2 is based on the REDFLASH technology with red and infrared light.

Measuring principle

The sensing technology is based on an oxygen-sensitive indicator. The respiration vials have an integrated sensor stipe (Figure 3) on the inside for measuring oxygen content in water. An adapter ring (Figure 4) is fixed by screws on the vials and an optical fibre cable is connected to the vials facing the integrated sensor stripe.

The optical fibre cable has a sensor surface on the tip. The tip excitates red light sinusoidal flashes to measure oxygen as fast as 10 milliseconds, based on REDFLASH technology (Figure 5).

Use of the REDFLASH technology allows for:

  • High precision of measurement
  • High reliability of the measurement
  • Low power consumption
  • Low cross-sensitivity (different molecules with similar chemical structure)
  • Fast response time
  • Low interference with biological systems performing autofluorescence (natural emission of light from structures (e.g. the mitochondria), molecules (e.g. NADPH) and amino acids (e.g. tryptophan and phenylalanine)) which may result in a stress response.

Red and Infrared light

The REDFLASH technology is based on excitated red light (613-630 nm) and an oxygen-dependent luminescence of near-infrared light (NIR; 760-790 nm). Luminescence is the spontaneous emission of light from the substrate. As demonstrated in figure 6a when there is low oxygen in the substrate, there is a high NIR-emission. When there is a high level of oxygen (6b), there is low NIR-emission.

The sinusoidal flashes of red light results in a phase-shift (Figure 7) of the NIR-readout by the FireStingO2 oxygen meter (termed "dphi" in the Firesting Logger software). The phase shift is logged and converted into an oxygen unit based on Stern-Vollmer-Theory.

 

 

Figure 6: Red light excited show luminiscence in the near infrared light (NIR). A) high NIR emission at low oxygen level. B) low NIR at high oxygen level.
Figure 7: Phase shift is the horizontal shift for a function.