title: Development of a medical fiber-optic pH sensor based on optical absorption.
abstract: A new fiber-optic pH sensor system has been developed. The sensor uses an absorbtive indicator compound with a long wave-length absorption peak near 625 nm; change in absorption over the pH range 6.8 to 7.8 is reasonably linear. The sensor is interrogated by a pulsed, red LED. Return light signal is split into short and long wave-length components with a dichroic mirror; the respective signals are detected by photodiodes, and their photocurrents are used to form a ratiometric output signal. In laboratory tests, the sensor system provided resolution of 0.01 pH, accuracy of +/- 0.01 pH, and response time of 30-40 s. Following gamma sterilization, laboratory sensor testing with heparinized human blood yielded excellent agreement (e.g., r = 0.992 for n = 42) with a clinical blood gas analyzer. Excellent sensor performance and low cost, solid-state instrumentation are hallmarks of this sensor-system design.
authors.affiliation: MetriCor Inc., Woodinville, WA 98072.
authors.forename: R
authors.initials: R
authors.lastname: Wolthuis
authors.forename: D
authors.initials: D
authors.lastname: McCrae
authors.forename: E
authors.initials: E
authors.lastname: Saaski
authors.forename: J
authors.initials: J
authors.lastname: Hartl
authors.forename: G
authors.initials: G
authors.lastname: Mitchell
mesh_terms: D000042:Absorption; D001391:Azo Compounds; D001784:Blood Gas Analysis / Q000295:instrumentation*; D002138:Calibration; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D005336:Fiber Optic Technology / Q000295:instrumentation*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D055100:Optical Fibers; D013242:Sterilization; D014227:Triazines
chemical_list: D001391:Azo Compounds; D007202:Indicators and Reagents; D014227:Triazines; C076690:6-chloro-N-(7-(2,4-dinitrophenylazo)-8-hydroxy-6-sulfo-2-naphthyl)-N'-(5,7-disulfo-2-naphthyl)-1,3,5-triazine-2,4-diamine