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.
OxyTrace+ is a multi-function Windows® program supplied with our range of PC-operated electrode control units for system configuration, calibration, data acquisition and analysis.
In liquid-phase systems such as Oxygraph+, Oxytherm+, Chlorolab 2+ and Chlorolab 3+, an automated 2-step calibration routine guides the user quickly and effectively through the system calibration process using electrode values measured from air-saturated and deoxygenated water. For gas-phase systems such as Leaflab 2+, an automated 3-step calibration routine using electrode values measured from ambient air, ambient +/- 1ml of injected/removed ambient air and a further measurement of ambient air is employed.
For electrode control units that provide automated light source control in systems such as Oxytherm+P, Chlorolab 2+, Chlorolab 3+ and Leaflab 2+, OxyTrace+ allows simple configuration of comprehensive PFD tables consisting of up to 20 individual light steps. Light intensity adjustments are performed automatically during the measurement. OxyTrace+ also allows calibration of the light source from a simple software routine. This requires the QTP1+ PAR/temperature sensor to be connected to the rear of the electrode control unit and placed into the reaction vessel prior to the addition of any liquids. In the Leaflab 2+ gas-phase system, calibration of the LH36/2R light source requires manual input of measured values at each individual calibration intensity step using the QSRED quantum sensor.
A tabbed interface allows a simple transition between the different data views including oxygen electrode (and if configured, auxiliary and external ion-selective electrode) realtime output, a split screen showing realtime rate of change above the oxygen signal and tabulated numerical data.
Post-acquisition analysis tools allow automatic calculation of oxygen rates from user-defined rate intervals. For Oxytherm+P, Chlorolab 2+, Chlorolab 3+ and Leaflab 2+ systems, additional analysis tools automatically calculate rates of change for defined PFD light steps with a calculation of quantum yield presented at the end of a measurement. All files are saved as Comma Separated Values (CSV) data files opening effortlessly in external data processing packages such as MS Excel®.
OxyTrace+ will run on all supported Microsoft operating systems.
Oxygraph+ systems are supplied with the following components:
- DW1/AD: Liquid-phase electrode chamber
- OXYG1+: Electrode control unit
- A2: Membrane applicator to assist with smooth application of electrode membrane
- A3: Top plate key and alignment jig to dismantle and reassemble DW1/AD for cleaning
- S2/P: Pack of 5 magnetic followers
- S3: Pack of 2 replacement borosilicate glass reaction vessels
- S4: PTFE membrane (0.0125mm x 25mm x 33m)
- S7A: Replacement O-rings for electrode chamber
- S16: Cleaning kit for the S1 electrode disc.
Oxygraph+ electrode control unit
- Measuring range:
- Oxygen: 0% – 100%
- pH: 0pH – 14pH
- Aux: 0V – 4.096V
- Signal inputs:
- S1 O2 electrode (SMB)
- pH/ISE (BNC)
- Auxiliary (8-pin Mini-Din)
- Oxygen: 0.0003% (24-bit)
- pH: 0.0006pH (16-bit)
- Aux: 62.5µV/bit (16-bit)
- Polarising voltage: 700mV
- Input sensitivity: 0nA – 9000nA
- Magnetic stirrer: Software controlled 150rpm – 900rpm in % steps
- Sampling rate: 0.1 – 10 readings/s
- Microcontroller: 16-bit high-performance CPU running at 32 MHz
- ADC: Dual, Low-power, 16/24-bit Sigma Delta
- Communications: USB2.0
- Analogue output: 0V – 4.5V O2 signal
- Dimensions (HWD): 200mm x 110mm x 60mm
- Weight: 0.45 Kg
- Power: 12V dc @ 100mA, 90VAC – 264VAC @ 1A.
DW1/AD electrode chamber
- Suitability: Liquid-phase respiration/photosynthesis
- Construction: Clear cast acrylic
- Sample chamber: Precision-bore, borosilicate glass tube
- Sample volume: 0.2ml – 2.5ml
- Temperature control: Water jacket connected to thermoregulated circulating water bath
- Dimensions (DH): 65mm x 105mm
- Weight: 100g
- Plunger: Gas-tight, variable-height plunger assembly with stoppered central bore for sample additions.
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
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