Optrodes

FIGURE 8.4 Configurations for several different kinds of optieal fiber sensing systems are shown. The eommon faetor in all these systems is the use of an optical fiber as an integral element in the system, either to earry light to and from diserete sensors (often referred to as optrodes), or as sensitive elements themselves (intrinsie fiber sensors). Courtesy, AT T Bell Laboratories. 

Moreno-Bondi M.C., Wolfbeis O.S., Leiner M.J.P., Schaffar B.P.H., Oxygen optrode for use in a fiber optic glucose biosensor, Anal. Chem. 1990 62 2377. 

Trettnak W., Wolfbeis O.S., Fiber optic cholesterol biosensor with an oxygen optrode as the transducer Anal. Biochem. 1990 184 124. 

An integral part of a fibre optic sensor is the light source. Its primary task is to deliver an appropriate light, which possesses such features as an optical power suitable to interact with an analyte or an indicator from the optrode, a wavelength matched to the spectral properties of the sensors in order to obtain the highest sensitivity, and, in dependence on the construction of the sensor, polarisation, short pulse etc. There are many various light sources utilised in the fibre optic chemical sensors. They differ in spectral properties, generated optical power and coherence. 

Oehme I., Prokes B., Murkovic I., Werner T., Klimant I. Wolfbeis O.S., LED-compatible copper(II)-selective optrode membrane based on lipophilized Zincon, Fresenius J. Anal. Chem. 1994 350 563-567. 

Lapp H., Spohn U., Janasek D., An enzymatic chemiluminescence optrode for choline detection under flow injection conditions, Anal. Lett. 1996 29 1-17. 

Abdel-Latif M.S., Guilbault G.G., Peroxide optrode based on micellar-mediated chemiluminescence reaction of luminol, zlna/. Chim. Acta 1989 221 11-17. 

Voraberger H.S., Kreimaier H., Biebemik K., Kem W., Novel oxygen optrode withstanding autoclavation technical solutions and performance, Sens. Actuat. B 2001 74 (1-3) 179-185. 

W. Trettnak, M.J. Leiner and O.S. Wolfbeis, Optical sensors. Part 34. Fibre optic glucose biosensor with an oxygen optrode as the transducer, Analyst, 113(10) (1988) 1519-1523. 

H. He, H. Li, G. Mohr, B. Kovacs, T. Wemer, and O. S.Wolfbeis, Novel type of ion-selective fluorosensor based on the inner filter effect An optrode for potassium, Anal. Chem, 65, 123-127... 

Y. Kawabata, T. Kamichika, T. Imasaka, and N. Ishibashi, Ion-selective optrode using hexadecyl-acridine orange attached on poly(vinyl chloride) membrane, Anal. Chem, 62, 2054-2055 (1990). 

Performance Characteristics of the Fluorescence Optrode Cure Sensor... 

Figure 2. Tool-mounted optrode with glass-plate interface.

The run-to-run reproducibility of the profile shape of the FOCS fluorescence-intensity signal is good however, the reproducibility of the absolute intensity values is unsatisfactory. The run-to-run variations in the fluorescence intensities are caused by the differences in resin thickness at the small area "viewed" by the optrode. In addition, substantial resin flow takes place during cure, causing the resin thickness to vary as a function of cure time. However, since this variation in resin thickness mi t be reproducible from run-to-run (if other cure parameters remain unchanged), it may be possible to develop a suitable... 

Tool-mounted optrode (TMO). The cure-monitoring experiments described here were conducted with a "tool-mounted" optrode (TMO) arrangement (5,6) (Figure 2) which is Ideally suited for the manufacturing environment where minimum interference with the laminate layup work is desirable. The use of a tool-mounted optrode is as simple as the use of tool-mounted thermocouples currently in wide use. Indeed, the TMO provides viscosity/degree-of-cure information on the cure state of the surface layer only. However, knowledge of the cure state of the surface layer permits determination of the cure states in the bulk based on the available models (1,2). 

The optrode-laminate Interface. The exact geometrical arrangement in which a tool-mounted optrode is in contact with the layer of resin covering the carbon fibers and the dimensions of the layer "viewed" by the optrode strongly affect the level of the FOCS intensity signal at a given cure time. 

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