Description
The AquaProbe Optical Electrodes work on the principle of Dynamic Luminescence Quenching. While the principle of dynamic luminescence quenching is primarily used for dissolved oxygen, these optical electrodes are designed for parameters like:
- Turbidity: These often use a nephelometric technique, where a light beam is shone into the water, and the scattered light is measured at a 90-degree angle to determine the turbidity (cloudiness) caused by suspended particles.
- Chlorophyll, Blue-Green Algae, Rhodamine, Fluorescein, Refined Oil, CDOM/FDOM: These sensors typically work by exciting specific compounds in the water with a light source and then measuring the fluorescence emitted by those compounds at a different wavelength. The intensity of the emitted fluorescence is proportional to the concentration of the target substance.
All Optical Electrodes, with the exception of the Turbidity Electrode, employ fluorescent measurement techniques. Fluorescence measurement are ideal for researchers who are interested in detecting the presence or absence of a specific substance in reasonable concentrations and measuring relative fluorescence changes that can be used as an indication of increasing or decreasing concentrations. Interference from microbiological species and compounds which fluoresce at similar wavelengths and differences in fluorescence caused by temperature, ambient light and turbidity can all cause inaccuracies.
Installation
To fit an Electrode, first remove the sleeve from the AquaProbe by unscrewing at the blue split-line. Apply a small amount of silicone grease to the threaded section and the O-ring of the AUX Electrode (see photograph). ENSURE NO GREASE IS APPLIED TO THE GOLD CONTACTS. Use a clean cloth or tissue paper, polish the gold contacts ensuring they are completely clean. Carefully insert the electrode into the socket and tighten firmly by hand until the O’ring is completely compressed. Do not over-tighten or use any tool (such as pliers). After fitting the Electrode, replace the Sleeve and ensure the Sleeve End Cap is fitted.
Once a new electrode is fitted it is essential to carry out a full two-point calibration prior to use. Calibration solutions are available with the relevant optical electrode. The carry case has space to hold suitable calibration solutions
Calibration
| Electrode | Excitation Peak Wavelength | Detection Range | Calibration Solution | Calibration High Point |
|---|---|---|---|---|
| Chlorophyll | 470nm | >630nm | RHOD-CAL | 500µg/L |
| Blue-Green Algae Phycocyanin (BGA-PC) | 590nm | >655nm | RHOD-CAL | 100µg/L |
| Blue-Green Algae Phycoerythrin (BGA-PE) | 520nm | >575nm | RHOD-CAL | 8µg/L |
| Fluorescein Dye | 470nm | >550nm | FSCEIN-CAL | 100µg/L |
| Rhodamine WT | 520nm | >575nm | RHOD-CAL | 100µg/L |
| Refined Oil | 285nm | 330nm – 370nm | REFOIL-CAL | 10ppm solution of 1-5, naphthalenedisulfonic acid disodium salt |
| CDOM | 365nm | 450nm – 520nm | CDOM-CAL-600 | 100µg/L Quinine Sulphate |
| Turbidity | 850nm | 850nm | TURB-1000 | 1000 NTU |
Low Point Calibrations should be done using a bottle of Still Mineral Water.
The Optical Electrodes are designed to work with specific AquaProbe sensors and the correct probe should be matched to the correct probe. AP-LITE, AP-2000, AP-5000 and AP-6000/AP-7000 probes are available on the pages linked below.
