Ocean Optics - Inventor of the World's First Miniature Spectrometer
Ocean Optics - Inventor of the World's First Miniature Spectrometer

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Ocean Optics - Inventor of the World's First Miniature Spectrometer

Fiber Optic pH Sensors

The Fiber Optic pH Sensor system consists of a fiber optic probe designed to hold immobilized colorimetric indicator dye materials, plus a light source, spectrometer and OOISensors Software. You can supply your own indicator material, or select from our line of transparent or reflective films. Calibration involves recording spectra in high and low pH samples, and in at least one pH standard such as a NIST-traceable buffer.

Transmissive and Reflective pH Films

Transmissive films are for clean, transparent samples. These films consist of a cellulose mechanical matrix surrounded by a hydrophilic polymer that entraps the indicator dye. Reflective films are used for turbid or absorbing media.

Film Performance

When immersed in water, the film dyes may leach very slowly over time and will have to be replaced. The film response rate is slow (on the order of minutes), being limited by diffusion of ions into the material. Increasing stirring speed, ionic strength and temperature all tend to increase the response rate and do not affect the pH measurement. Nearly any aqueous sample environment is suitable, as are some solvents.

TP300 Probe

The TP300-UV-VIS Probe is a chemically inert PEEK transmission probe that can be equipped with a tip for mounting transmissive films in the optical path. Light is directed via one fiber through the mounted film to a mirror. Then light is redirected back through the film to a receive fiber that returns the light to the spectrometer. The sample is free to flow over the sides of the film. By using an RTP-2-10 (adjustable 2-10 mm) Transmission Tip, the TP300-UV-VIS can be used for routine transmission measurements.

Note: Only recommended for use with spectrometers with 50 m slits.

TP300-UV-VIS:  Call for Price

Item Specification
Fiber type (2) 300 m core diameter fibers (1 illumination, 1 read)
Outer diameter: 3.175 mm
Length: 107.9 mm for probe, 2 meters for fiber
Optics: Fused silica
Internal materials: Aluminum
Pathlength: 16 mm with RT-PH Tip
Outer materials: PVC fiber jacketing, PEEK polymer for sleeve
Connector: SMA 905
Operating temperature: Up to 220 C with PEEK sleeve

RF200 Probe

The RFP200-UV-VIS Reflective Film Probe consists of a 6-around-1 fiber bundle in a chemically inert 6.35-mm OD Torlon body. The open tip of the probe screws onto the body to hold 3.17-mm to 4.76-mm discs of reflective indicator material. The 6-fiber leg attaches to the light source; the central fiber leg connects to the spectrometer. The sample has access to the sensing material from one side only.

RFP200-UV-VIS:  Call for Price

Transmissive Indicator Dye Films for pH Sensing

Item Film Type pH Range

Color Change

PH-BCG-TRANS Bromocresol green 5.0-9.0 Yellow-Blue

No Resale

The goods identified herein are subject to the condition that they shall not, nor any portion of them, by way of trade or otherwise, be lent, resold, or otherwise conveyed to a subsequent borrower, purchaser, or transferee unless Purchaser has a currently valid License, Distribution, or Sales Representative Agreement expressly granting permission to so convey the goods. Please contact our sales department if you are interested in obtaining a license.

pH References

Spectrophotometric Determination of Freshwater pH Using Bromocresol Purple and Phenol Red. Author: Yao, Wensheng; Byrne, Robert H. Source: Environmental Science and Technology v. 35 no6 (Mar. 15, 2001) p. 1197-201

Spectrophotometric Determination of Seawater pH Using Phenol Red. Author: Robert-Baldo, Gillian L.; Morris, Michael J.; Byrne, Robert H. Source: Analytical Chemistry v. 57 (Nov. 1985) p. 2564-77

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