High signal at zero oxygen

MitoPedia O2k and high-resolution respirometry: O2k-Open Support

Description

A high signal at zero oxygen may be observed during zero calibration (R0). First, check the quality of the dithionite solution. The following instructions show how to distinguish between a defective sensor head and an electrical leak current.

Reference: Zero calibration, OroboPOS-Connector

Leak current test

O2k-series J and XB

Unplug the SmartPOS from the O2k-main unit.
Remove the membrane from the SmartPOS and wash the cathode and anode with distilled water.
Switch on the O2k and start DatLab.
Record the signal for 10 min.
Connect the SmartPOS to the O2k-main unit. Set an event in DatLab called "SmartPOS".
Record the signal for 10 min.
The leak current of each individual component should be stable and below 0.001 µA (DatLab 8). If the SmartPOS is giving a high leak current a sensor service frequently solves the problem. If you have any uncertainties, please forward the file to the technical support.

O2k-series D-I and XA

Unplug the POS-Connector from the O2k-main unit and unscrew the OroboPOS from the POS-Connector. Screw the POS to the blue part of the perspex housing.
Remove the membrane from the POS and wash the cathode and anode with distilled water.
Switch on the O2k and start DatLab.
Record the signal for 10 min.
Connect the POS-Connector to the O2k-main unit without the POS. Set an event in DatLab called "POS-Connector".
Record the signal for 10 min.
Screw the POS to the POS-Connector. Set an event in DatLab called "POS".
Record the signal for 10 min.
The leak current of each individual component should be stable and below 0.001 µA (DatLab 8) or V (DatLab 7 and previous versions). Depending which component is giving a high leak current, a sensor service, followed by cleaning the electrical connections and drying the OroboPOS (without membrane) or the POS-Connector in an oven at up to 60 °C for 1-2 h frequently solves the problem. If you have any uncertainties, please forward the file to the technical support.

O2k-series A-C

Plugging or unplugging of the POS-Connector while the main unit is switched on could damage the POS-Connector of O2k-series A-C. Therefore, the following should be started with the O2k switched off.

Unplug the POS-Connector from the O2k-main unit and unscrew the OroboPOS from the POS-Connector. Screw the POS to the blue part of the perspex housing.
Remove the membrane from the POS and wash the cathode and anode with distilled water.
Plug the POS-Connector to the main unit.
Switch on the O2k and start DatLab.
Record the signal for 10 min.
Screw the POS to the POS-Connector. Set an event in DatLab called "POS".
Record the signal for 10 min.
The leak current of each individual component should be stable and below 0.001 V (DatLab 7 and previous versions). Depending which component is giving a high leak current, a sensor service, followed by cleaning the electrical connections and drying the OroboPOS (without membrane) or the POS-Connector in an oven at up to 60 °C for 1-2 h frequently solves the problem. If you have any uncertainties, please forward the file to the technical support.

References

[1] Cleaning the electrical connections

[2] MiPNet19.18B POS-service

[3] MiPNet06.03 POS-calibration-SOP

[4] MiPNet14.06 Instrumental O2 background

Example

First, the OroboPOS-Connector and the POS were disassembled and disconnected from the main unit. Second, the OroboPOS-Connector was connected to the O2k-Main unit without the OroboPOS. Third, the OroboPOS was connected to the OroboPOS-Connector without membranes. After each step, the O₂ raw signal [V] was recorded for 10 min. The marks were set to the O₂ raw signal [V] to evaluate the leak current.

Figure 1. Leak current test. Upper panel: Leak current is in the range of ±0.00099 V. Lower panel: Leak current is higher than 0.00099 V when the OroboPOS-Connector is connected to the O2k-Main unit and when the OroboPOS is connected to the OroboPOS-Connector, indicating a potential electrical problem of both, the OroboPOS-Connector, and the OroboPOS.