Oxygen Sensor (Model 1302)

Oxygen Sensor (Model 1302)

This is a Clark-type polarographic sensor with a 22 micron diameter platinum cathode and silver/silver chloride anode connected by a buffered potassium chloride electrolyte solution.

  • Used in conjunction with both the 782 Dual-Channel Oxygen Meter and 928 Six-Channel Oxygen Meter
  • May be used with or without medium stirring
  • Exhibits highly stable signal output
  • Very low rate of oxygen consumption
  • Compatible with all Strathkelvin accessories

Item# Description U.S. List Price Quantity
69-3006 Microcathode Oxygen Electrode Model 1302 with polypropylene jackets
69-3004 (SI-1320F) 1302 Oxygen electrode with jacket for FEP membranes
69-3007 Oxygen Electrode Service Kit
69-3005 (SI-021) FEP oxygen electrode service kit
69-3008 Electrolyte Solution, 125 ml
69-3013 O-Rings, Box of 25 SI130
69-3014 (SI-045) Polyproplyene membraned jackets, box of 6
69-3034 (SI-023) Polyproplyene membraned jackets, box of 30
69-3011 Electrode Jacket (with Hole) for FEP Membranes
69-3010 FEP Membranes, pkg. of 15
69-3035 (SI-031) Abrasive membranes, box of 6
69-3036 (SI-043) O-rings for FEP membranes, 25 pack
69-3001 Model 782 Dual channel oxygen meter with automatic respirometry software
69-3002 (SI-929) Model SI-7929 Six channel oxygen meter with standard respirometry software
69-3018 Respiration Cell RC 300, 0.31 ml
69-3019 Respiration Cell RC 350, 1.0 - 3.0 ml
69-3033 Mitocell Miniature Respirometer MT 200, 50/100 µl
69-3021 6 Electrode Respirometer RC 650
69-3016 MicroCell Model MC 100
69-3023 Flow Cell Model FC 100
69-3015 (SI-067) Modified syringe for MT-200A and MS-200A, 5
69-3017 (SI-066) Modified syringe for MT-200 and MS-200, 1
69-3029 (SK-650) Replacement glass cells for RC-650, 6 pack
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View the complete application table here.

The 1302 Oxygen Electrode is a precision electrode with a very small diameter. Its rate of oxygen consumption is extremely low so that when used with the relatively low permeability polypropylene membranes, most of the resulting oxygen gradient is confined to the distance between the outside of the membrane and the cathode surface. Consequently there is no requirement for physical movement of the solution to replenish the oxygen at the outer surface of the membrane.

The 1302 is compatible with all Strathkelvin accessories including the MS-200/200A, RS-650, RC-650, RC-350, and RC-300 respiration cells and the MT-200, MC-100 and FC-100 flow cells

The relaxation of a stirring requirement for the 1302 results in a small stirring artifact (2-3%) when the electrode has been calibrated in stirred solution and is then used in an unstirred environment (and vice versa). In general, electrodes using the fast-responding, highly permeable FEP membranes have a large O2 flux through the membrane. This causes the electrode to behave as a macrocathode making it necessary to stir.

Unfortunately, it is not possible to build a fast electrode with no stirring requirement, and it is important to note that most Clark-type electrodes require stirring. Only in a microcathode electrode such as the 1302, fitted with a low permeability membrane, is stirring not required.

Stirred Clark-type electrodes

The Clark-type oxygen electrode consists of a probe at whose tip is an exposed gold or platinum cathode and a silver or silver/silver chloride anode. When the anode and cathode are polarized so that the cathode is held at a voltage of -0.6 to -0.8 volts relative to the anode, and connected via a solution of electrolyte such as KCl, the following reaction will occur at the anode:

4Ag > 4Ag + + 4e and 4Ag + + 4Cl- > 4AgCl

Simultaneously, at the cathode, any oxygen which is present is reduced:

O2 + 2H2O + 4e > 4OH-

Thus for each oxygen molecule reduced, 4 electrons of current flow in the circuit. Oxygen is therefore continually consumed as it is reduced to OH at the cathode. In practice, the anode and cathode are covered by an oxygen permeable membrane to exclude other species which would interfere. The KCl electrolyte is buffered to remove the OH produced in the cathode reaction. As oxygen is removed at the cathode, a pO2 gradient is set up which extends outwards into the surrounding medium. In unstirred water, oxygen therefore diffuses inwards along the pO2 gradient. Because of the pO2 gradient, the outside of the electrode membrane is effectively sensing a lower pO2 than that in the surrounding water. For this reason, most Clark electrodes require the water to be stirred. The size of the signal generated by the electrode is proportional to the flux of oxygen molecules to the cathode.

Last Revision 6.28.12


This is a Clark-type polarographic electrode, with a 22 micron diameter platinum cathode and silver/silver chloride anode, connected by a buffered potassium chloride electrolyte solution.

In the normal configuration the cathode is covered with a relatively low permeability polypropylene membrane, in order for the electrode to be used in unstirred solutions or where minimal stirring is required. With these membranes, there is a relatively slow response time. For fast response, as required for rapidly respiring enzyme preparations, a thin FEP membrane (used with a special electrode jacket) is used. Rapid stirring of the medium is then necessary. The electrodes are not temperature compensated and require to be used at controlled temperatures (within + or -0.05°C). They should always be used in the electrode holder, so that only the tip of the electrode is exposed to the medium.

Response time at 37°C:
Polypropylene membranes 18 sec. for 90% change
FEP membranes 6 sec. for 90% change
Oxygen consumption (polypropylene membranes) 0.5 to 3x10-10mg O2/min
Temperature coefficient 2% per °C
Resolution of 928 and 782 meter 0.1% with 1302 electrode*

*The display resolution of the 982 and 782 meter is 0.1%. The A/D converter is capable of at least 0.01%, so you can work on an expanded scale. However, the limit is normally set to about 0.1% by the noise level of the 1302 electrode.

Last Revision 6.28.12

  1. Reduction of Copper(II) by Iron(II)
    Matocha CJ, Karathanasis AD, Rakshit S, Wagner KM
    J Environ Qual. 2005 Aug 9;34(5):1539-46
1302electrode_manual.pdfOxygen Sensor Electrode Manual (Model 1302)