Tomas B. Hirschfeld

Single fibre optic fluorescence pH probe

Fibre optic sensing is a growing technology in analytical chemistry. Scattering, absorbance, reflectance and luminescence spectroscopic measurements have been made using fibre waveguides. Fluorescence is particularly suited for use in fibre sensing because of its sensitivity and versatility, and the ease with which this type of measurement may be implemented with a single fibre optic.The probe configuration used in this study for pH measurement consists of fluorescein isothiocyanate (FITC) covalently bonded to a porous glass bead. This bead is attached to a single, multi-mode optical fibre, which conducts both the excitation and emission radiations. The increase in fluorescence intensity, as the acid form of the immobilised FITC is converted to its basic form, is related to the pH. The dynamic range of this miniature probe is pH 3–7 and this can be extended by decreasing the dye loading. The response time is between 20 and 35 s, depending on the capacity.

Clinical measurements using fiber optics and optrodes

Fiber optics, optrodes, and fluorescence spectroscopy have been combined to form the new technology of remote fiber fluorimetry (RFF). Both in-vivo and in-vitro clinical measurements can be made by using this technique. The optrode, a fiber termination with preselected chemical or physical properties, is attached to the distal end of the optical fiber so that specific, in-situ measurements can be made. RFF systems for pH, blood pressure, oxygen, and carbon dioxide are being completed, and other optrodes are in the development stages.