Oxygen sensing Clark electrode

The idea of separating the gas sample by a gas-permeable membrane from the actual internal sensing element is common to several types of electrochemical and some optical sensors. The potentiometric Severinghaus electrode and the amperometric oxygen Clark electrode have already been discussed. Actually, most types of sensors can be used in this configuration and the conductometric sensor is not an exception (Bruckenstein and Symanski, 1986). 

Fig. 10.2. Sensing principles for the determination of the biochemical oxygen demsind (BOD), (a) Immobilized cells on the surface of a Clark electrode and (b) batch assay with cells in suspension and with a redox mediator.

The importance of molecular oxygen sensing is unquestionable, given the role this species plays in nature. According to the required application field, different sensor types have been developed through the years, whether for measurements in the gas-phase or in liquids [82-84]. From the very beginning, silicones have been present in the fabrication of oxygen sensors. The amperometric Clark electrode for waterborne Oj measurements, developed in 1956, was basically formed... 

We note here that the widely employed Clark oxygen electrode differs fundamentally from these devices (18, 63). The Clark device is similar in construction to the apparatus of Figure 2.4.5, in that a polymer membrane traps an electrolyte against a sensing surface. However, the sensor is a platinum electrode, and the analytical signal is the steady-state current flow due to the faradaic reduction of molecular oxygen. 

An acid phosphatase (AP) hybrid biosensor was developed using a thin layer of potato tissue coupled to an amperometric GOD-based biosensor based on internal sensing of H202. The reversible inhibition of AP was utilized for the determination of malathion, paraoxon methyl, paraoxon, and aldicarb with limits of detection of 0.5 ppb for paraoxon methyl, and 40 ppb for aldicarb. The tissue-based biosensor exhibited a longer shelf life and abetter reliability on the amperometric results than a bi-enzymatic sensor with purified AP and GOD. A similar biosensor was also developed using a potato layer with a Clark-type dissolved oxygen electrode. ... 

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