Patent ID: 7608460

Claim:
A system for measuring pH, comprising: (a) a light source for exciting a fluorescent species, wherein the fluorescent species has a first emission intensity at a first emission wavelength and a second emission intensity at a second emission wavelength; (b) a first emission detector for measuring the first emission intensity; (c) a second emission detector for measuring the second emission intensity; (d) an excitation lightguide for transmitting excitation light from the light source to the fluorescent species, wherein the lightguide comprises a first terminus proximate to the light source and a second terminus distal to the light source; (e) a first emission lightguide for transmitting emission from the fluorescent species to the first emission detector, wherein the lightguide comprises a first terminus proximate to the detector and a second terminus distal to the detector; (f) a second emission lightguide for transmitting emission from the fluorescent species to the second emission detector, wherein the lightguide comprises a first terminus proximate to the detector and a second terminus distal to the detector; (g) a probe housing the distal termini of the excitation lightguide, first emission lightguide, and second emission light guide; and (h) an assembly for receiving the probe, the assembly comprising: (i) a housing for receiving the probe, wherein the housing is adapted for receiving the probe at a first end and terminating with a window at the second end, the window being transparent to the excitation and the emission light, (ii) a tip member reversibly connectable to the housing's second end, wherein the tip member is adapted to receive liquid from a sample to be measured, and (iii) a fluorescent species immobilized on a substrate intermediate the tip member and the window, wherein the fluorescent species immobilized on the substrate is in liquid communication with the sample during the measurement, and wherein the window physically isolates the probe member from the fluorescent species immobilized on the substrate.