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Macro 900 Operation Manual
15.2. PT 1552 Freshwater Blue-Green Algae (phycocyanin) Probe
Freshwater Blue-Green Algae can be measured by the MAP 2000/2100 using
the optional PT 1552 optical probe.
15.2.1.
Principle of Operation
The PT 1552 Blue Green Algae optical probe is a submersible, fixed response
fluorometer, which provides excitation at 590nm and detects any resultant
fluorescence above 655nm.
The electrode induces the phycocyanin to fluoresce, then measures the longer
wavelength light which is emitted as a result of the fluorescence process.
15.2.2.
Limitations of Use
Determination of BGA-PC in the field using fluorescence measurement
techniques will never be as accurate as measurements made in a lab using
either cell counting or analysis of molecular phycocyanin after its extraction
from cells.
Factors adversely affecting accuracy include:
Interference from other microbiological species and compounds, which
fluoresce at similar wavelengths.
Differences in the fluorescent response between various species of BGA.
Differences in the fluorescent response caused by temperature.
Differences in the fluorescent response caused by ambient light.
Interference caused by turbidity.
Fluorescence measurement techniques are ideal for researchers who are
interested in detecting the presence or absence of a specific substance and
measuring relative fluorescence changes that can be used as an indication of
increasing or decreasing concentrations.
Fluorescence
measurement
measurement. In order to obtain more accurate results, data obtained
with the fluorometer in the field should be post-calibrated with data
from standard laboratory analysis of grab samples acquired during the
study.
15.2.3.
Calibrating the BGA-PC Electrode
The BGA-PC probe has two calibration points. Careful calibration is essential in
order to ensure consistent and reliable results.
When a BGA-PC probe is first installed, it MUST be calibrated at both points
in order to set the probe's relative sensitivity and establish its slope.
Subsequently, a single point (Zero) calibration should be carried out daily.
Calibration of the BGA-PC probe Zero point is normally carried out during
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