S1 Oxygen Electrode Disc
Since its original design in the early 1970s by Tom Delieu and David Walker, the S1 Clark-type oxygen electrode disc remains largely unchanged – a true testament to the quality and reliability of the sensor. The S1 consists of a platinum cathode and silver anode set into an epoxy resin disc and is prepared for use by trapping a layer of 50% saturated KCl solution beneath an oxygen-permeable PTFE membrane. A paper spacer placed beneath the membrane acts as a wick to provide a uniform layer of electrolyte between anode and cathode.
When a small voltage is applied across these electrodes (with the platinum negative with respect to the silver), the current which flows is at first negligible and the platinum becomes polarised (i.e. it adopts the externally applied potential). As this potential is increased to 700 mV, oxygen is reduced at the platinum surface, initially to hydrogen peroxide H2O2 so that the polarity tends to discharge as electrons are donated to oxygen (which acts as an electron acceptor). The current which then flows is stoichiometrically related to the oxygen consumed at the cathode.
When connected to the electrode control unit, the S1 provides a fast, effective and accurate method of detecting small changes in oxygen concentration.
LD1/2 Electrode Chamber
The LD1/2 leafdisc electrode chamber is a simple device for measuring oxygen exchange from a 10cm2 leafdisc mounted within a sealed, gas-tight sample-chamber.
The LD1/2 is constructed from black acetal with a cast acrylic top window allowing the sample to be evenly illuminated for photosynthesis measurements using the LS2 high-intensity white light source.
A prepared S1 oxygen electrode disc mounts into the base of the LD1/2 with the dome of the electrode forming the floor of the sample-chamber.
Temperature of the sample can be accurately controlled by connecting an external circulating water bath (not included) to the water jacket inputs of the LD1/2.
LS2 White Light Source
The LS2 light source is a high-intensity (100W) tungsten-halogen light source which is powered from a stabilised power supply.
The lamp housing contains a cooling fan, infrared reducing “Hot-Mirror” and optics to provide light with minimum variation of intensity across the beam and little divergence from parallel. 2 slots are provided to accept 50mm square optical filters or a manual shutter-plate.
A range of light intensity steps may be achieved by adding permutations of the 4 A5 neutral density filters supplied (0.1,0.3,0.6 and 1.0 O.D.) to attenuate the light intensity. Maximum sample illumination intensities vary depending on the type of electrode chamber in use.
When used with the DW1 electrode chamber the LS2 can achieve a maximum intensity of 1,800 µmol m-2 s-1 when mounted horizontally with respect to the electrode chamber.
Oxyview Control Unit
The OXYV1 Oxyview control unit has been designed as a convenient, low-cost oxygen electrode control unit for teaching studies of photosynthesis and cellular respiration using the oxygen electrode measurement technique.
The Oxyview control unit is fully compatible with the range of oxygen electrode chambers produced by Hansatech Instruments thus allowing a wide range of different assays to be performed in both liquid and gas-phases.
The Oxyview is configured and controlled via a front mounted control panel featuring 4 touch-sensitive buttons. Configuration is achieved by navigating through a series of simple menu screens and following the displayed guidelines for each step of the setup process. These configuration steps include setting of the stirrer speed (for liquid-phase measurements) and back-off and gain settings. Once configured, the Oxyview control unit provides an accurate and stable reading of the oxygen content of the sample in question.
The Oxyview control unit is powered by a 12V DC wall cube which connects directly to the rear of the unit. Also at the rear is a 0V – 5V analogue output. This allows the measured values from the control unit to be logged to an external recording device such as a chart recorder or similar datalogger accepting a 0V – 5V analogue input.
System Components
Leafview 1 Systems are supplied with the following components:
- LD1/2: Oxygen electrode chamber
- OXYV1: Oxyview electrode control unit with integral magnetic stirrer
- S1: Oxygen electrode disc and SMB-SMB connection cable
- LS2: Tungsten-halogen white light source
- A2: Membrane applicator to assist with smooth application of electrode membrane
- A5: Set of 5 neutral-density filters
- S4: Reel of PTFE membrane (0.0125mm x 25mm x 33m)
- S8B: Set of replacement O-rings for LD1/2
- S14: Set of 3 stainless steel discs, capillary matting and foam spacer for leafdisc electrode chambers
- S15: 3-way gas taps and 1ml disposable syringe for leafdisc electrode chambers (4 taps + 2 syringes)
- S16: Cleaning kit for the S1 electrode disc.
Technical Specifications
Oxyview 1 electrode control unit
- Measuring range: Oxygen: 0% – 100%
- Signal inputs: Oxygen electrode (SMB)
- Resolution: 10 x 10-6 μmols/ml at 20°C
- Polarising voltage: Selectable between 0.4V – 0.9V (0.7V recommended default)
- Gain: Coarse: x1, x2, x5, x10, x20, x50, x100. Fine: 1mV steps
- Back off: Signal back off in 1mV steps
- Analogue output: 0V – 5V electrode signal
- Dimensions (HWD): 90mm x 135mm x 85mm
- Weight: 320g
- Power: 95V – 260V universal input mains supply. Output 12V DC 2.5A
LD1/2 electrode chamber
- Suitability: Gas-phase respiration/photosynthesis
- Construction: Black acetal
- Sample chamber: Leaf chamber (7.5cc)
- Sample area: 10cm2
- Optical Ports: Cast acrylic top window
- Temperature control: Water jacket connected to thermoregulated circulating water bath
Dimensions (DH): 95mm x 75mm
- Weight: 350g.
S1 oxygen electrode disc
- Electrode type: Clark-type polarographic oxygen sensor
- Electrode output: Typically 1.6µA at 21% O2
- Residual current: Typically 0.04µA in 0% O2
- Response time: 10 – 90% typically <5 seconds
- Oxygen consumption: Typically <0.015µmol/hr-1
LS2 light source
- Lamp Type: 100W tungsten-halogen (50W available on request)
- Power Supply: Mains, stabilised power supply. 12V DC 10A. 120/240V 60/60Hz
- Intensity Adjustment: Via combinations of 4 neutral-density filters (supplied)
- Max Intensity in DW1: 1,800 μmol m-2 s-1
- Dimensions:
- Light housing: 145mm x 65mm x 75mm. Weight 1.0kg
- Power supply: 86 mmx 150mm x 140mm. Weight 1.4kg.
Publications
One of the extensions of the Google search facility is Google Scholar. It allows you to search through vast archives of peer-reviewed published papers and journals that have been posted online.
Use the tool below to enter search terms as required. As an example, hansatech instruments Leafview 1 System has already been entered into the search box. Press the "Search" button to view the Google Scholar results for this search string.
Admittedly, some of the results link to journals which require subscription in order to view the publications but even so, we have found this facility to be a valuable tool.
