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6.26 Blue-Green Algae (aka Cyanobacteria)-Phycocyanin (PC)-6131 Calibration
ALWAYS ensure that the temperature sensor is completely submerged during all calibrations.
Failure to submerge the sensor can result in false calibrations. And, ALWAYS allow time for the
temperature of the standard and the sensor to equilibrate.
In most cases blue-green algae sensors are not calibrated prior to deployment but
rather the performance is checked using a fluorescent dye and a blank solution.
To ‘calibrate’ a blue-green algae probe, discrete water samples should be collected
from the field. At the time of collection, the sensor signal should be recorded. The
sample must then be stored properly and a cell count must be performed in the lab
according to Standard Methods. This will generate a quantitative blue-green algae concentration. The cell count data
is then correlated with the field sensor readings in order to post-calibrate the data and provide semi-quantitative blue-
green algae
data.
For more information on the BGA-PC sensor, please refer to the 6-Series User Manual, section 5.16, Principles of
Operation-BGA-PC.
You may use a 1-point calibration in a 0 cells/mL solution to zero out the sensor, however, YSI recommends using a
2-point calibration using a 0 cells/mL solution to zero out the sensor and a second standard of a fluorescent dye.
The following section explains how to prepare the recommended dye solution. If you wish to simply zero out the
instrument, you may proceed to the ‘1-Point Calibration’ section. If you will calibrate and check the sensor using
a known count of PC-containing BGA cells, you may proceed to the ‘2-Point Calibration using BGA-PC Counts.’
Preparation of Dye Standard for BGA-PC Sensor Calibration
For dye calibrations, YSI recommends using a Rhodamine WT solution. The dye does not necessarily increase the
accuracy of the sensor; it is used as a check of the sensor’s function.
The Rhodamine WT standard can photodegrade quickly after preparation. Calibrate the BGA-PC sensor no
more than 5 days after preparation.
YSI uses Rhodamine WT from the below-noted supplier. The solution is approximately 20% Rhodamine WT.
KEYSTONE RHODAMINE WT LIQUID (Part #70301027)
Keystone Aniline Corporation
2501 W. Fulton Street
Chicago, IL 60612
1. Weigh exactly 0.500 g of the 20% Rhodamine concentrate.
2. Quantitatively transfer the viscous liquid to a 1000 mL volumetric flask and fill the flask to the top
graduation.
3. Mix well. This solution contains 100 mg of Rhodamine WT per 1000 mL of water (100 mg/L).
4. Transfer exactly 1.0 mL of the solution prepared in the above step (100 mg/L) to a 1000 mL volumetric flask
and then fill to the top graduation with pure water.
5. Mix well to obtain a solution that is 100 ug/L (0.10 mg/L) in water (1000:1 dilution of original concentrate).
6. Store and refrigerate the original concentrate in a darkened glass bottle to retard decomposition.
7. Also store the dilute standard in a refrigerated environment.
If you wish to calibrate using this solution, please continue reading.
NOTE
NOTE
6.2