Differential oxygen sensors

Figure 3. Oxygen profiles in four different types of commercial MAP hams over their shelf life measured with the oxygen sensors system. Changes between Days 10 and 15 and subsequent differentiation are seen.

Appelhoff RJ, Tian YM, Raval RR, Turley H, Hands AL, Pugh CW, Ratcliffe PJ, Gleadle JM. Differential function of the prolyl hydroxylases, PHDl, 2 and 3 in the regulation of hypoxia inducible factor (HIF). J. Biol. Chem. 2004 279 38458-38465. Berra E, Benizri E, Ginouves A, Vofinat V, Roux D, Pouysse-gur J. HIF prolyl-hydroxylase 2 is the key oxygen sensor setting low steady-state levels of HIF-la in normoxia. EMBO J. 2003 22 4082-4090. 

Abstract We review recent progress in wide bandgap thin-film and nanorod sensors made from GaN or ZnO and related materials for applications in the detection of gases such as oxygen, carbon dioxide and hydrogen. Practical aspects are covered, such as the use of differential sensor pairs to eliminate the effects of temperature variations and of the effect of humidity on the detection sensitivity. 

For any enzyme-based electrode, there is the problem of finite substrate affinity determined by enzyme MichaeUs constant (Kn,) that, typically, falls well below the analytical concentration range needed for a linear response in undiluted samples. For oxidases, there is also the need for oxygen co-substrate. Venous blood samples have relatively low PO2 levels which could compromise response. A material-based solution to the problem is to use a manbrane barrier that (1) reduces the transport of analyte to the enzyme and (2) maintains a relative permeability to O2. In one early approach, substrate-restricting microporons manbranes were used modified with O2 permeable silicone [10] in another, silicone emnlsion was used [11] both these barriers promoted the differential transfer of O2. High-volume production of sensors is less... 

FIGURE 6.18 Time Trace of Temperature Sensors and Differential Pressure Transducer with Corresponding Images of Screen using (a) Gaseous Helium and (b) Gaseous Oxygen as Pressurants. 

---