Ocean Optics Transmissive pH Probe User Manual

Transmissive pH Probe

Instructions

Overview

Ocean Optics’ fully integrated pH systems provide full spectral analysis to help eliminate errors from
dye leaching or from changes in turbidity, temperature, and ionic strength. Inherent calibration based
on the physical properties of the immobilized indicator dye eliminates the need for frequent
calibration. The ratiometric algorithm provides accurate and reproducible measurements at a high
resolution.

The Transmissive pH Probe’s form factor provides very fast response with high signal strength,
though is limited to clear, non-turbid solutions. These sensors are compatible with aqueous solutions,
ethanol/methanol solutions, ammonia, peroxides, and sodium hypochlorite solutions.

Transmissive Probes and Patches

The pH sensory substrates use a sol gel sensing material coated onto a transmissive patch. The
immobilized indicator dye(s) are encapsulated into the sol gel matrix, allowing for the diffusion of
ions while preventing leaching of the dye. The sensors provide very accurate measurements in the
biological range, from pH 5 to 9. Advantages of these probes over traditional potentiometric devices
include faster response time, easy storage and no maintenance, and low cost. These are especially
useful for monitoring low conductivity samples such as boiler water, where electrode devices fail.

Software Interface

The Transmissive pH Probes can be used with a desktop system or the Jaz handheld spectrometer. The
desktop system uses a special SpectraSuite software module that allows for easy calibration,
convenient pH readings, customizable data logging, and comprehensive export of data and calibration
values.

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pH Probe Instructions

Transmissive pH Probe Benefits

 Chemistry

- Proprietary Organically Modified Sol Gel (ORMOSIL) formulation engineered to
maximize immunity to ionic strength sensitivity

- Compatible with some organic solvents (i.e. acetone, alcohols, aromatics)
material chosen over typical polymer method, allowing for a faster response

- time, versatility in the desired dopants, greater chemical compatibility, flexible coating,
and enhanced thermal and optical performance

- Indicator molecule allows high resolution measurement in biological range (pH 5-9)

 Simplified algorithm takes analytical and baseline wavelengths into account to reduce errors

caused by optical shifts

 Sterilization

- Transmissive patches are autoclavable

- Transmissive patches are gamma and ethylene oxide sterilizable

 Maintenance

- Long-term storage

- Dry or wet storage

- Single point reset

 Applications

- Organic solvents

- Low ionic strength cooling water

- Biological Processes

- Environmental

 Durable design allows probe to survive conditions/shocks that would cause glass electrodes to

break

◊ Sol-Gel

Fiber Optic pH Sensor System Components

The Fiber Optic pH Sensor system consists of the following:

 Transmissive pH probe (T300-UV/VIS or VIS/NIR)
 Ocean Optics VIS-NIR spectrometer (or Jaz Sensor module) that covers 350–1100 nm (slit

options 25, 50, 100, 200)

 SpectraSuite Spectrometer Operating Software for reading values
 Light source (LS-1 Tungsten Halogen Light Source or a white LED)
 Transmissive pH patches, pack of 5 (PH-BCG-TRANS)

Calibration requires recording spectra in high and low pH samples, as well as in at least one pH
standard solution (such as a NIST-traceable buffer).

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pH Probe Instructions

For field measurements, the Ocean Optics handheld Jaz spectrometer offers an easy and portable
solution. An SD card contains a script that allows you to use the factory calibration or a complete
calibration, shows live pH values and provides the ability to save data right onto the SD card.

Probe Storage/Lifetime

Probes can be stored dry at room temperature for any amount of time. As they are used, the patches
may slowly leach indicator dye from the sensing material. As a rule,

at pH 11 falls below 0.1, the patch should be discarded and replaced

1). The patch’s lifetime depends on frequency of use, harshness of the samples it is exposed to, the
temperature of samples, and other environmental factors.

once the maximum absorbance

(assumes a reference of pH

Nature of Samples

The analyte solutions being measured should have a pH within the biological range (pH 5-9) for
accurate readings. Data obtained from analyte solutions that register values above or below this range
should not be considered valid within the specifications of the sensors. Aqueous solutions,
ethanol/methanol solutions, peroxides, ammonia, and sodium hypochlorite solutions are all compatible
with the sensor material. Samples being used with the transmissive probe should be optically
transparent, having no turbidity or sediment present. It is also ideal to have analyte solutions that are
colorless, though colored liquids can be compensated for.

Response time is dependent on the ionic strength of the solution, with higher salinity samples
responding notably faster. For example, using the calibration buffers of pH 5 – 8 will show a 90%
response in 10 seconds or less, but when pure D.I. water is being measured, more time is needed to
equilibrate at a final value. Make sure that the probe is sufficiently submersed into the analyte
solution, and that there are not bubbles present. To ensure no bubbles remain, shake the probe back
and forth through the liquid to knock them free. Likewise, more accurate results will be obtained if the
probe is rinsed once or twice with the analyte solution after calibration. This removes any residual
buffer solution that may contaminate your sample.

When immersed in solution, the film dyes may leach very slowly over time and will have to be
replaced. The film response rate is limited by diffusion of ions into the material; therefore increasing
stirring speed and ionic strength tend to increase the response rate.

pH Probe Set Up

The following procedures describe how to connect and calibrate the transmissive pH probe using a
VIS-NIR spectrometer, a light source and SpectraSuite software. See your spectrometer, light source
and SpectraSuite manual for more detailed installation information (available at

http://www.oceanoptics.com/technical/operatinginstructions.asp).

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