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Proceedings Paper

pH optrode for the complete working range
Author(s): Gargi Vishnoi; Tara Chand Goel; P. K. C. Pillai
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Paper Abstract

We report a fast response and inexpensive optical sensor capable of measuring pH in the range of 0.5 to 13.5 units with good resolution. Three indicator dyes viz. Bromocresol Green, Bromothymol Blue and Nile Blue were used to fabricate the sensor head. ion-exchange resin, Amberlite IRA 400, was powdered and immobilized by these dye solutions. In order to prepare sensing membranes, Polyvinyl chloride was dissolved in Tetrahydrofuran and the solution was poured on to a glass plate. Before the membrane was completely dry, the immobilized resin powder was uniformly sprinkled so that the granules are properly glued to it. A bundle of fibers was attached to the membrane mechanically to carry the light from the source to the membrane and collect the reflected optical signal. He-He laser was used as a light source. The experimental results show a linear dependence of pH value on reflected optical signal for the pH range of 0.5 to 13.5 with the resolution of 0.02 unit. The optrode was also characterized by studying the effect of ionic strength and temperature of the solution on the probe response.

Paper Details

Date Published: 11 January 1999
PDF: 7 pages
Proc. SPIE 3538, Process Monitoring with Optical Fibers and Harsh Environment Sensors, (11 January 1999); doi: 10.1117/12.335760
Show Author Affiliations
Gargi Vishnoi, Indian Institute of Technology (India)
Tara Chand Goel, Indian Institute of Technology (India)
P. K. C. Pillai, Indian Institute of Technology (United States)

Published in SPIE Proceedings Vol. 3538:
Process Monitoring with Optical Fibers and Harsh Environment Sensors
Michael A. Marcus; Michael A. Marcus; Anbo Wang, Editor(s)

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