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Optical pH Sensor Spots

  • Original REDFLASH-technology
  • Contactless measurements in closed containers
  • Contamination-free due to non-invasive measurement
  • No need of a reference electrode
  • Minimal cross-sensitivity to ionic strength
  • For long-term measurements
  • Easy integration into your transparent vessel

The new pH sensor spots are based on a unique optical detection principle (REDFLASH technology) and allow contactless pH measurements within closed containers through a transparent window. The sensor spot is fixed at the inner side of the window and read-out with optical fibres connected at the outside to the new FireSting pro multi-analyte device. The REDFLASH technology utilizes red excitation light and uses the NIR emission of the new pH sensors to overcome background fluorescence of the sample which was already successfully applied for our optical oxygen sensors. The sensor spot is covered with an optical isolation protective layer to prevent disturbance of the pH measurement from e.g. external illumination or strong luminescent samples.

Different pH ranges. Optical pH sensors are sensitive to a pH range of 2-3 pH units. Sensors are offered for two different ranges for pH measurements between pH 6.0 to 8.0 and pH 7.0 to 9.0. Robust calibration is ensured by using PyroScience pH buffer capsules at pH 4.0 and pH 10.0. Our pH sensors were especially designed for minimal cross sensitivity to ionic strength and the outstanding photostability of the sensors enable high sampling rates over long periods.

Typical Applications

  • General measurements in liquids
  • Single-Use (Micro)Bioreactors
  • Integration into cell culture flasks 
  • Photosynthesis / respiration measurements

Compatible oxygen meters

FireSting pro (FSPRO-x)

Available Sensors

Item No. Description Pricing
in EU*
PHSP5-PK7 pH Spots for measurements between pH 6.0 – 8.0 (8 spots) Ø5 mm, PET foil 75 µm, with optical isolation 240 €
PHSP5-PK8 pH Spots for measurements between pH 7.0 – 9.0 (8 spots) Ø5 mm, PET foil 75 µm, with optical isolation 240 €


Item No. Description Pricing
in EU*
SPGLUE Silicone Glue for gluing sensor spots to container walls (ca. 90 ml) 30 €
SPADBAS Basic Spot Adapter (4 pieces) for 0-2mm windows
50 €
SPADLNS Lens Spot Adapter for 2-6mm windows (for ST-plugs, needs SPFIB) 50 €
SPFIB Optical Fiber (1m length), ST-plugs at both ends 50 €
SPFIB-CL2 Optical Fiber (2m length), ST-plugs at both ends 60 €
SPFIB-BARE Bare Optical Fiber (1m length), ST-plug + one polished end 50 €
SPFIB-BARE-CL2 Bare Optical Fiber (2m length), ST-plug + one polished end 60 €

* Only EU-Prices shown. Contact us for pricing outside EU. Not for resale.


More details…


Silicone Glue for Sensor Spots (SPGLUE). This silicone glue can be used for gluing sensor spots onto the inner side of the containers, where the oxygen measurement should be performed in. Generally, every transparent silicone glue based on acetic acid can be used for this purpose. The actual delivered brand of silicone glue might differ from the product image.


Basic Spot Adapter (SPADBAS). Set of 4 basic spot adapters providing precise fixation for the optical fibers SPFIB or SPFIB-BARE at transparent container walls. The spot adapter should be glued to the window with an appropriate adhesive (e.g. silicone glue SPGLUE).


Lens Spot Adapter (SPADLNS). The lens spot adapter provides a precise fixation for the optical fiber SPFIB at transparent containers with a wall thickness of ca. 2-6mm. A flexible re-adjustable cable binder is included, allowing quick positioning e.g. on laboratory flasks. Not applicable if submersed in water.



Optical Fiber (SPFIB). The optical fiber SPFIB is used for connecting the spot adapters SPADBAS or SPADLNS to the optical oxygen meter FireStingO2. There are ST-connectors at both ends. Standard cable lengths of 1m or 2m are available.



Bare Optical Fiber (SPFIB-BARE). The bare optical fiber SPFIB-BARE is used for connecting the basic spot adapter SPADBAS to the optical oxygen meter. It has a straight cut polished fiber end, which has no metallic parts. Therefore, SPFIB-BARE can be used in water baths or salt water applications.


Less details…


Given for 2-point calibrated pH sensors (pH 4.0 and 10.0) in physiological solutions at 25°C.

PK7 - Version pH
Optimum measuring range 6.0 - 8.0
Resolution at pH 7.0 0.005
Accuracy at pH 7.0 +-0.05
Drift at pH 7.0 <0.005 / day
PK8 - Version pH
Optimum measuring range 7.0 - 9.0
Resolution at pH 8.0 0.005
Accuracy at pH 8.0 +-0.05
Drift at pH 8.0 <0.005 / day
All versions
Temperature range 5 to 50°C
Photostability Negligible photodegradation
Response time t90 < 60 sec. at 25°C
Interferences Surfactant solutions, organic solvents or commercial buffer solutions (typically contain stabilizer) must not be used
Salinity Compensation of ionic strength (IS) for different application areas (10 mM – 500mM IS) possible
Background fluorescence Minimized due to REDFLASH technology
Cleaning Rinsing with deion. water only
Storage time Original packaging (unpacked) 12 months at room temperature
Storage conditions Dark and dry conditions
Calibration 2-point calibration, pH offset adjustment possible
Calibration solution PyroScience buffer capsules or a self-made buffer must be used. Important: other pH buffers must not be used and can damage the sensor irreversibly
Optical isolation The sensor is equipped with an optical isolation to minimize interference from strong external illumination and light-sensitive / fluorescent samples