Xylem EXO Series User Manual page 74

Calibration (Chl + BGA-PC)
5.8 4.4
Total Algae
Chlorophyll
This procedure calibrates Chlorophyll RFU or Chlorophyll μg/L. If the user has both units selected, then this
procedure must be performed twice, once for each unit, to completely calibrate the parameter.
For 2-point calibrations, one standard must be clear water (0 μg/L), and this standard must be calibrated
first. The other standard should be in the range of a known chlorophyll content of the water to be monitored.
Two general types of standards can be used: (a) phytoplankton suspensions of known chlorophyll content,
determined by employing the extractive analysis procedure described in Standard Methods for the
Examination of Water and Wastewater, or by analyzing the suspension in situ using a laboratory fluorometer,
and (b) dye solutions whose fluorescence can be correlated to that of chlorophyll.
For option (b), we recommend using a 625 μg/L Rhodamine WT dye solution (for detailed instructions, see
section 5.10), and the solution is used in the calibration steps below.
µg/L – 1- or 2-point
This procedure will zero your fluorescence sensor and use the default sensitivity for calculation of chlorophyll
concentration in μg/L, allowing quick and easy fluorescence measurements that are only semi-quantitative
with regard to chlorophyll. However, the readings will reflect changes in chlorophyll from site to site, or over
time at a single site.
Pour the correct amount of clear deionized or distilled water into the calibration cup. Immerse the probe
end of the sonde in the water.
In the Calibrate menu, select BGA-PC/Chlor, then select Chl μg/L. Select either a 1- or 2-point calibration.
Enter 0 for first standard value and 66 for second standard value.
Click Start Calibration. Observe the readings under Current and Pending data points. While stabilizing,
click the Wipe Sensors button to activate the wiper to remove any bubbles. When data are Stable (or data
shows no significant change for approximately 40 seconds), click Apply to accept this calibration point.
Next place the sensors in the Rhodamine WT standard. Click Proceed on the pop-up window. Observe
the readings under Current and Pending data points. While stabilizing, click the Wipe Sensors button to
activate the wiper to remove any bubbles. When data are Stable (or data shows no significant change for
approximately 40 seconds), click Apply to accept this calibration point.
Click Complete. View the Calibration Summary screen and QC score. Click Exit to return to the sensor
calibration menu, and then the back arrows to return to main Calibrate menu.
Rinse the sonde in tap or purified water and dry the sonde.
RFU – 1- or 2-point
RFU is a percent full scale output; it outputs relative fluorescence from 0-100%. This calibration procedure is
recommended if you are also using grab samples to post-calibrate in vivo chlorophyll readings.
The sonde will report relative values of fluorescence in the sample being measured. These values can be
converted into actual chlorophyll concentrations in μg/L by using a post-calibration procedure, after the
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