Xylem EXO Series User Manual page 79

Rhodamine WT Dye Solution for Total Algae Sensor
A
Read and follow all the safety instructions and MSDS documentation supplied with the dye before
proceeding. Remember that only trained personnel should handle chemicals.
Preparation
Use the following procedure to prepare a Rhodamine WT solution for use as a sensor stability check reagent
for the EXO Total Algae (Chlorophyll and Blue-green Algae) sensor:
1. Purchase Rhodamine WT dye in solution form, which can vary somewhat in nominal concentration.
Recommended supplier for a solution that is approximately 2.5% in Rhodamine WT:
Fluorescent FWT Red Dye (item #106023)
Kingscote Chemicals
3334 South Tech Blvd.
Miamisburg, OH 45342 USA
1-800-394-0678
2. Accurately transfer 5.0 mL of the Rhodamine WT solution into a 1000 mL volumetric flask. Fill the
flask to the volumetric mark with deionized or distilled water and mix well to produce a solution that
is approximately 125 mg/L of Rhodamine WT. Transfer this standard to a glass bottle and retain it for
future use.
3. Accurately transfer 5.0 mL of the solution prepared in the above step to a 1000 mL volumetric flask
and then fill the flask to the volumetric mark with deionized or distilled water. Mix well to obtain a
solution, which is 0.625 mg/L in water (a 200:1 dilution of the concentrated solution).
4. Store the concentrated standard solution in a glass bottle in a refrigerator to retard decomposition. The
dilute standard prepared in the previous step should be used within 24 hours of its preparation.
Discard the used standard. When Rhodamine standards are required in the future, perform another dilution
of the concentrated Rhodamine WT solution after warming it to ambient temperature.
Effect of temperature on fluorescence
The intensity of the fluorescence of many dyes shows an inverse relationship with temperature. This effect
must be accounted for when calibrating the EXO Total-Algae sensor with Rhodamine WT. Enter the μg/L
calibration value from the table below that corresponds to the temperature of the standard.
Temp (˚C)
μ g/L Chl
30 56.5
28 58.7
26 61.3
24
63.5
22
66
20
68.4
Temp (˚C)
μ g/L BGA-PC
7.4 18
8.5 16
9.2 14
12
9.7
10
10.4
8
11.1
μ g/L Chl μ g/L BGA-PC
70.8 11.4
73.5 12.4
76 13.1
78.6 13.8
81.2 14.5
83.8 14.7
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