User Manual
Optical pH Sensors | User Manual
© PyroScience GmbH 20
6 APPENDIX
6.1 pH Measuring Principle
The optical pH sensor is based on the successful PyroScience REDFLASH technology. The
sensor consists of a pH insensitive reference indicator and a pH sensitive luminescent
dye. Both are excited with red-light (more precisely: orange-red at a wavelength of 610-
630 nm) and show bright luminescence in the near infrared (NIR, 760-790 nm).
If the pH indicator is de-pronated at high pH, its fluorescence is quenched and only the
NIR emission of the reference indicator is measured. If the pH gets more acidic, the pH
indicator is protonated and emits bright NIR luminescence and the emission of both
indicators is detected.
The
REDFLASH technology impresses by its high accuracy, high reliability and low
power consumption.
The red-light excitation of the
REDFLASH indicators significantly reduces interferences
caused by autofluorescence and reduces background fluorescence from biological
samples / media.
The measuring principle is based on a sinusoidally modulated red excitation light. This
results in a phase-shifted sinusoidally modulated emission in the NIR. The
PyroScience
read-out device measures this phase shift, which is then calculated into pH.