Fiber-optic electrode

A fiber-optic electrode was fabricated for the simultaneous generation and transmission of electrochemical luminescence by preparing a transparent electrode on the optical and surface of a fiber-optic. The opto-electrochemical properties of the micro-optical device were characterized in solutions containing the compounds required for luminol luminescence. The validity of sensitive measurement of electrochemiluminescence to be employed in a homogeneous immunoassay was evaluated by using potential step excitation of luminol in the presence and in the absence of hydrogen peroxide. 

Spectroelectrochemistry, a combination of optical spectroscopy and electrochemistiy has provided a powerful means for eluddating complex redox processes near solution-ekcbodc interfaces f 15.161. A union of transparent electrodes with fiber-optics provides a new strategy for designing new biosensing devices, provided they can be assembled into one instrument (fiber-optic electrode) that will generate and transmit a luminescence signal in response to the substance to be determined. 

We report here the performance characteristics of the fiber-optic electrode by app iqg the device to the electrochemiluminescence of luminol to clarify the feasibility of luminol as an electrochemiluminescent label for a sensitive homogeneous immunoassay. 

Fabrication of fiber-optic electrode. Platinom was sputtered on the flat end surface of a plastic fiber-optic (diameter 2 mm, length ISO cm) courteously supplied by Mitsubishi Rayon Co. Sputtering was performed by a Hitachi minisputter for 5 min at 15 mA. The platinum counter electrode was prepared as illustrated in Figure 2. The thin platinum layer for the working electrode was connected to a lead wire with silver paste, while that for the counter electrode was connected with solder. The contact points were then fixed in place and insulated by sealing with epoxy resin. 

Figure 2. Schematic illustration of the configuration of a fiber-optic electrode for the generation and simultaneous transmission of electrochemiluminescence.

AIZAWAETAL. Fiber-Optic Electrode for OptodeOrochenucol Biosensors 133... 

Figure 3. Experimental apparatus for the characterization of fiber-optic electrode.

The cell volume was less than 2 mL, therefore the potential of the fiber-optic electrode was referred to the reference electrode (Ag/AgCl) through a salt bridge. 

The fiber-optic electrode was employed for the oxidation of luminol. A phosphate-buffered solution (0.1 M, pH 70) was used as an electrolyte, and the scan rate was 5 mV/sec. 

The interval of a step-wise potential application for the excitation of luminol was also investigated. Figure 7 shows that a duration of the negative potential application of 5 s and that of the positive potential application of 15 s was the best conation for the greatest luminescence generation. Under the optimum condition, electrochemiluminescence of luminol was detected with the fiber-optic electrode in the concentration range from 10 to 10 3 M as shown in Figure 8. 

The principal uses of PCTFE plastics remain in the areas of aeronautical and space, electrical/electronics, cryogenic, chemical, and medical instmmentation industries. AppHcations include chemically resistant electrical insulation and components cryogenic seals, gaskets, valve seats (56,57) and liners instmment parts for medical and chemical equipment (58), and medical packaging fiber optic appHcations (see Fiber optics) seals for the petrochemical /oil industry and electrodes, sample containers, and column packing in analytical chemistry and equipment (59). 

Normal reflection optics have been used to advantage with bulk electrode materials. Examples of this type of spectroelectrochemical cell are shown in Figure 9.11 [67]. Simple bifurcated fiber-optic waveguides are used to direct source light onto reflective bulk electrode surfaces and to collect the reflected light for transmission to a detector. This is a simple means for performing spectroelectrochemical experiments at bulk metal electrodes that cannot be as... 

Figure 17.11 Transmission spectroelectrochemistry cell designed for use with room-temperature haloaluminate melts and other moisture-reactive, corrosive liquids, (a) Auxiliary electrode and reference electrode compartments, (b) quartz cuvette containing the RVC-OTE, (c) brass clamping screw, (d) passageway between the separator and OTE compartment, (e) fritted glass separator, (f) A1 plate, (g) lower cell body (Teflon), (h) upper cell body (Teflon). This cell is normally used inside a glove box and is optically accessed with fiber optic waveguides. [From E. H. Ward and C. L. Hussey, Anal. Chem. 59 213 (1987), with permission.]...

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