Aquaprobe
®
AP-700, AP-800 & AP-2000 Instruction Manual
10401-00870 Rev R
26. Appendix 5. Optical Electrodes Detailed Specification and FAQs
26.1. What are the excitation and detection wavelengths?
Each Aquaread
®
Optical Electrode (with the exception of Turbidity) is effectively a stand-
alone, fixed frequency fluorometer, specially tuned to excite and detect fluorescence of
selected substances in water.
The Turbidity electrode is not a fluorometer. This electrode employs a Nephelometric
measurement technique in accordance with ISO 7027.
The following table shows the excitation peak wavelengths and detection ranges for each
electrode.
Electrode
Excitation Peak
Wavelength
Detection Range
Chlorophyll
470nm
>630nm
Blue-Green Algae
Phycocyanin (BGA-PC)
590nm
>655nm
Blue-Green Algae
Phycoerythrin (BGA-PE)
520nm
>575nm
Fluorescein Dye
470nm
>550nm
Rhodamine WT
520nm
>575nm
Refined Oil
285nm
330nm – 370nm
CDOM
365nm
450nm - 520nm
Turbidity
850nm
850nm
Each fluorometer electrode (with the exception of the Refined Oil Electrode) emits short
pulses of high energy light at the excitation wavelength and responds to fluorescence in the
detection range. The deep UV excitation of the Refined Oil Electrode operates on a 15
second on / 15 second off duty cycle.
26.2. How does the Refined Oil sensor work?
The Refined Oil sensor detects volatile organic compounds (VOCs) that are found in
petroleum derivatives. These include benzene, toluene, ethylbenzene, and xylenes (BTEX).
The sensor is a fixed frequency
in situ
fluorometer that uses deep UV wavelengths (285nm)
to excite the VOCs. An emission filter is then used to detect any fluorescence generated by
the VOCs between 330 and 370nm.
The electrode measures the VOCs immediately in front of the sensor face so will measure
at whatever depth the probe is lowered to. Naturally, the probe will only detect compounds
that are actually mixed/dissolved in the water, not those floating on the surface.
The Refined Oil electrode is ideal for customers who are interested in detecting the
presence or absence of VOC’s and measuring relative fluorescence changes that can be
used as an indication of increasing or decreasing concentrations.
The electrode is not intended for absolute, quantitative measurements. This can only really
be done using Gas or Liquid Chromatography in a laboratory although if grab sample data
is available, a Grab Sample Factor (GS Factor) can be input on the calibration screen in
order to improve the accuracy of future readings.
© 2017 Aquaread
®
Ltd.
www.aquaread.com
Page 132 of 141